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The temperature dependence of the structural and magnetic properties of wolframite-type FeWO4 was studied in situ by high-pressure neutron diffraction. Neutron diffraction measurements were performed with the XtremeD instrument at the Institut Laue-Langevin up to a maximum pressure of 8.7(4) GPa and a minimum temperature of 30.0(5) K. The diffraction data were analyzed via Rietveld refinements. We found that despite producing a contraction of 5% of the volume, the maximum pressure applied in this study does not modify the Shubnikov space group below magnetic order. However, the orientation of magnetic moments and the Néel temperature are slightly modified with the pressure, which is expected according to the preexistent understanding of magnetism in wolframites. We also determined a pressure–volume equation of state of FeWO4 at 300 K, which is compared with previous x-ray diffraction studies and density-functional theory calculations. [ABSTRACT FROM AUTHOR]

The temperature dependence of the structural and magnetic properties of wolframite-type FeWO4 was studied in situ by high-pressure neutron diffraction. Neutron diffraction measurements were performed with the XtremeD instrument at the Institut Laue-Langevin up to a maximum pressure of 8.7(4) GPa and a minimum temperature of 30.0(5) K. The diffraction data were analyzed via Rietveld refinements. We found that despite producing a contraction of 5% of the volume, the maximum pressure applied in this study does not modify the Shubnikov space group below magnetic order. However, the orientation of magnetic moments and the Néel temperature are slightly modified with the pressure, which is expected according to the preexistent understanding of magnetism in wolframites. We also determined a pressure–volume equation of state of FeWO4 at 300 K, which is compared with previous x-ray diffraction studies and density-functional theory calculations. [ABSTRACT FROM AUTHOR]

Lead-free piezoelectric ceramics of (1 − x)K0.5Na0.5NbO3-xCaTiO3 were fabricated, and their crystal structure, microstructure, and electrical properties were systematically studied. Rietveld refinement of the x-ray diffraction data and Raman spectroscopic analyses revealed a composition-dependent structural phase transition: three phase transitions, namely, from a pure orthorhombic phase for x ≤ 0.02 to a mixed phase of orthorhombic and tetragonal phases (0.03 ≤ x ≤ 0.08) and finally another mixed phase of tetragonal + cubic for x = 0.10 and 0.15 at room temperature (RT). The morphological study reveals a decrease in grain size along with a more uniform distribution of grains as the concentration of CaTiO3 (CT) increases; notably, a homogeneous distribution of grains is observed for x = 0.05. The temperature-dependent dielectric properties show two phase transitions, from orthorhombic to tetragonal (TO-T) and tetragonal to cubic (TC), for unmodified K0.5Na0.5NbO3 (KNN). However, both the phase transition temperatures (TO-T and TC) decrease, and the transition peaks broaden with an increase in CT substitution, and for x > 0.06, the TO-T shifted below RT. The broadening of the transition peak at TO-T may be due to the relaxation behavior. Among the prepared samples, the 5 mol. % CT-modified KNN shows the optimum electrical properties (d33 = 114 pC/N, ɛr = 412, and 2Pr = 15.25 μC/cm2) at RT. The enhanced electrical properties for x = 0.05 are due to the coexistence of orthorhombic and tetragonal phases, facilitating easy polarization rotation and flattening of the free energy profile. A phase diagram has been constructed based on the information gathered from the temperature-dependent dielectric measurements, RT x-ray diffraction, and Raman spectroscopy data and is discussed in detail. [ABSTRACT FROM AUTHOR]

(Bi0.5Na0.5)1−xBaxTiO3 lead-free ferroelectric ceramics were synthesized via the conventional solid-state reaction method. Structural and dielectric properties were investigated as a function of the doping concentration, considering x = 0, 2, 5, 8, 10, 12, 16, and 18 at. % Ba. The structural analyses were carried out from the x-ray diffraction technique, including the Rietveld refinement method, and Raman spectroscopy. Results confirmed the formation of the perovskite structure, revealing different crystalline symmetries, depending on the Ba2+ concentration: the single rhombohedral ferroelectric phase (R3c) for x = 0 and 2 at. %; coexistence of both rhombohedral ferroelectric (R3c) and tetragonal antiferroelectric (P4bm) phases for x = 5 at. % Ba; the single tetragonal antiferroelectric phase (P4bm) for x = 8 at. % Ba; coexistence of two tetragonal phases (antiferroelectric P4bm and ferroelectric P4mm) for x = 10 at. % Ba; and the single tetragonal ferroelectric phase (P4mm) for x = 12, 16, and 18 at. % Ba. The characteristics of the phases' transition, investigated from dielectric analysis, revealed the presence of two dielectric anomalies, which indeed have been associated to different phases' transitions, one of them showing relaxor-like characteristics. The obtained results offer new insights for a better understanding on the features of the phase diagram for the studied ceramic system, according to the different observed crystalline symmetries (ferroelectric and antiferroelectric) in a very wide doping concentration. In the light of the obtained results, a new phase diagram has been proposed considering a wider compositional range than those reported in the literature. [ABSTRACT FROM AUTHOR]

Chemical pressure is widely applied to antiferroelectrics (AFEs) as a criterion to enhance their antiferroelectricity. However, NaNbO3 (NN)-based ceramic with well-defined double polarization hysteresis (P–E) loops was rarely reported based on this strategy, and the effect of chemical pressure on antiferroelectricity remains to be understood. In this work, the Me cations (Me is Ti, Sn, Zr) with different ionic radii were introduced into the component system 0.76NaNbO3–0.20AgNbO3–0.04CaMeO3 to tune the negative chemical pressure and investigate its effect on antiferroelectricity. The enhancement of negative chemical pressure can effectively stabilize the AFE phase and reduce hysteresis, as revealed by the P–E loops and dielectric properties, which is further confirmed by the change in crystal lattice parameters and in situ Raman spectra. Rietveld refinement of x-ray powder diffraction reveals that the enhanced negative chemical pressure mainly reduces the cation off-centering displacement and [BO6] octahedral tilting angles. As a result, the 0.76NaNbO3–0.20AgNbO3–0.04CaZrO3 exhibits good reversibility of the electric field-induced antiferroelectric–ferroelectric phase transition and well-defined double P–E loops. This work reveals the underlying mechanism of chemical pressure and provides an effective way of discovering new NN-based AFEs. [ABSTRACT FROM AUTHOR]

In this study, the influence of La3+ substitution on the phase structure, microstructure, electrical and energy storage properties of (Sr 0.3 Bi 0.35 Na 0.335 Li 0.015) 1-x La x TiO 3 (SBNLT-xLa) ceramics with x = 0–0.05, using the solid-state combustion technique, was investigated. X-ray diffraction (XRD) patterns indicated a pure perovskite structure formed, along with coexisting rhombohedral and tetragonal phases in all ceramics. The Rietveld refinement analysis showed the tetragonal phase increased while the rhombohedral phase decreased with increased La3+ content. The morphology of the SBNLT-xLa ceramics displayed polygonal grain shapes and anisotropic grain growth. Average grain sizes increased from 2.01 to 2.43 μm as x increased from 0 to 0.01 and afterwards decreased as x increased further. Both the measured density and maximum dielectric constant (ɛ m) decreased from 5.48 to 5.29 g/cm3 and from 4667 to 2313, respectively, when x increased from 0 to 0.05. A decrease in the dielectric properties caused by the phase ratio shifting away from a morphotropic phase boundary (MPB) condition, poor microstructure and low density was produced with La3+ replacement. The maximum polarization (P max), remnant polarization (P r) and coercive field (E c) decreased with increased La3+ content. A decline in P r and E c improved the energy storage efficiency (ƞ) and energy storage loss (W loss), resulting in enhanced energy storage properties. At x = 0.02, the ceramic showed good energy storage properties (W total of 0.781 J/cm3, W rec of 0.624 J/cm3, W loss of 0.157 J/cm3 and ƞ of 79.8%), measured at 60 kV/cm. [ABSTRACT FROM AUTHOR]

SrLaAlO 4 -based ceramics have attracted intense interest due to their high quality factor (Qf) at high frequency. However, the poor resonant frequency temperature stability (τ f) limits their practical applications. Therefore, obtaining near-zero τ f while guaranteeing high Qf values is challenging. (Zn 0.5 Ti 0.5)3+ is utilized in Sr 0.6 Ca 0.4 LaAlO 4 ceramics to improve the τ f value effectively. The relationship between the structural features and microwave dielectric properties of Sr 0.6 Ca 0.4 LaAl 1- x (Zn 0.5 Ti 0.5) x O 4 (x = 0–0.5) ceramics has been systematically investigated by XRD, Rietveld refinement, SEM, Raman spectroscopy, TEM and P–V-L theory. XRD and Raman spectroscopy reveal the effect of (Zn 0.5 Ti 0.5)3+ substitution on the evolution of the crystal structure. According to the chemical bond theory, (Zn 0.5 Ti 0.5)3+ substitution leads to the increase of the dielectric constant, which is related to the increase of the average bond ionicity, with the La–O bond contributing predominantly to the bond ionicity. The variation of the Qf values can be attributed to the densification of the ceramics, the lattice energy of the Al/Zn/Ti–O bond, and the FWHM. The τ f value is strongly affected by the coefficient of thermal expansion of the lattice and the Al/Zn/Ti–O bond valence. It is noteworthy that excellent microwave dielectric properties are obtained for Sr 0.6 Ca 0.4 LaAl 1- x (Zn 0.5 Ti 0.5) x O 4 ceramics at x = 0.4: ε r = 21.62, Qf = 87,700 GHz (at 7.23 GHz), and τ f = −1.81 ppm/°C. The above work provides deeper insights into establishing the relationship between the K 2 NiF 4 -type crystal structure and dielectric properties from the perspective of chemical bond. [ABSTRACT FROM AUTHOR]

Herein, the Zn 2 V 2 O 7 electro-ceramic pyrovanadate was synthesized via a conventional solid-state reaction technique and calcined at 700 °C. The single phase formation of Zn 2 V 2 O 7 pyrovanadate crystallized in the monoclinic structure with C 12/ c 1 space group was confirmed by X-ray diffraction (XRD). The XRD powder diffraction profile was analyzed by Rietveld refinement to investigate the structural details of the compound. The complex impedance analysis was carried out in the frequency domain of 83 − 2 × 10 6 Hz over a temperature range of 453–613 K to study the electrical charge conduction and dielectric relaxation mechanism in the material which revealed the presence of the distribution of relaxation times with thermal charge activation. Depressed semicircles in the Nyquist plots were modeled by an equivalent circuit with configuration (R G C G)(R GB Q GB) which resolved the contributions of grains and grain boundaries towards the transport properties of the material. The electrical conductivity spectra followed Jonscher's power law behavior and the temperature variation of frequency exponent suggested correlated barrier hopping (CBH) as the governing transport mechanism in the Zn 2 V 2 O 7 pyrovanadate system. The comparison between scaling behaviors of imaginary parts of impedance and modulus advocated the temperature-independent nature of relaxation time distribution. The imaginary electrical modulus spectra were reproduced by the Kohlrausch, Williams, and Watt formulism, and the fitted parameters confirmed the non-Debye type nature of the dielectric relaxation. Further, the Haveriliak-Negami function was employed to investigate the dielectric response of the material which was found to be consistent with impedance, conductivity, and modulus analyses. The frequency dispersion of the tangent loss verified that the hopping mechanism was thermally activated. [ABSTRACT FROM AUTHOR]

Obtaining high-purity MAX-phase powders is a challenging issue. Therefore, in this article, the effects of two key parameters, including mechanical activation time (1, 2, and 3 h), and preheating temperature (800 and 1000 °C) were investigated on the formation mechanism of Ti 2 AlC MAX phase using mechanically activated (assisted) self-propagating high-temperature synthesis (MA-SHS) combustion method through thermal explosion mode. For this aim, a powder mixture of titanium, aluminum, and carbon with a stoichiometry ratio of (2:1:1) was used. Differential thermal analysis (DTA) was carried out to evaluate the effect of mechanical activation and preheating temperature of the formation temperature of the target MAX phase. Subsequently, the microstructural, phase analysis, chemical composition, and determination of surface chemical states studies were carried out through scanning electron microscopy (SEM), X-ray energy distribution spectroscopy (EDS) transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), and X-ray photoelectric spectroscopy (XPS), respectively. DTA results illustrated that applying mechanical activation alters the formation temperature, which leads to an increase in the purity of the MAX phase. The quantitative measurements were carried out using the Rietveld method to determine the purity of the achieved MAX phase. The results indicated that samples subjected to 2 h of mechanical activation at a preheat temperature of 1000 °C exhibited to contain 96.1 % of Ti 2 AlC MAX phase, which is the highest value among other specimens and the lowest amount of secondary and oxide phases (3.9 % of TiC) during the combustion synthesis process compared to other samples. [ABSTRACT FROM AUTHOR]

In this study, the estimated stress, strain, and crystallite sizes of different Mn-doped ZnO nanoparticles were calculated using the Williamson-Hall method and compared with the values obtained from the Debye-Scherrer formula. Moreover, defects, and magnetic properties of Mn-doped ZnO nanoparticles at different concentrations were investigated. The sol-gel method was used to synthesize nanoparticles. The X-ray diffraction and Rietveld analysis results confirm that the desired structure is formed and that no secondary phase is present up to an Mn concentration of x = 0.2. In and out of plane lattice parameters, cell volumes, bond length, atomic locality, and dislocation density (δ) were clarified. The grain size of the concentration-dependent samples was provided by scanning electron microscope. Photoluminescence (PL) spectra exhibited ultraviolet emission along with a broad band encompassing violet, blue, and red regions, attributed to defect-related and excitonic emissions. These emissions were notably influenced by synthesis conditions and doping elements and ratios. Electron spin resonance properties of the concentration-dependent samples were analyzed to figure out the g-factor through line widths of pike-to-pike (ΔHPP) of ESR spectra. Mn-doped ZnO nanoparticles exhibited ferromagnetism at room temperature. [ABSTRACT FROM AUTHOR]

Mg 3 Ga 2 TiO 8 ceramics were prepared using a solid-phase method. The ceramics sintered at 1440 °C exhibited excellent microwave dielectric properties (ε r = 12.07, Q × f = 89,270 GHz, and τ f = −40.7 ppm/°C). The typical spinel structure of the Mg 3 Ga 2 TiO 8 ceramic was confirmed through Rietveld refinement and Raman spectroscopy. High-resolution transmission electron microscopy indicated local lattice distortion in the Mg 3 Ga 2 TiO 8 ceramics, with a Vickers hardness of 12.53 GPa. The values of ε r and Q × f for the Mg 3 Ga 2 TiO 8 ceramics were affected by the relative density. The theoretical ε r obtained from the C-M equation was lower than the measured ε r , plausibly due to underestimation of the polarizability of the Ti ions. According to the P-V-L theory, Ti2-O1 has the highest f i value, contributing 29.92 % to ε r. The contribution rate of the Ga2-O1 bond to U was 35.76 %, with the greatest impact on Q × f. [ABSTRACT FROM AUTHOR]

In pursuit of the objective of implementing fifth-generation communication technology, a LiMg 2 P 3 O 10 microwave dielectric ceramic was developed in this study, and an ultra-wideband dielectric resonant antenna was fabricated. Rietveld refinement confirmed that the monoclinic crystal structure of LiMg 2 P 3 O 10 ceramics is constituted of MgO 6 octahedral chains and shared angle PO 4 tetrahedra. The impact of chemical bond characteristics on properties was explored through P-V-L theory. The primary contributions to the intrinsic properties were investigated through infrared spectroscopy. The LiMg 2 P 3 O 10 ceramics sintered at 830 °C were found to have the best microwave dielectric properties (ε r = 6.16, Q × f = 33,573 GHz (at 15.538 GHz), and τ f = −35.6 ppm/°C). A novel ultra-wideband dielectric resonant antenna with 53.7 % relative bandwidth, 6.53 dBi maximum gain and 81.7 % radiation efficiency was designed and fabricated. Its wide ultra-wideband characteristics makes it suitable for signal transmission in modern wireless communication systems. [ABSTRACT FROM AUTHOR]

The futuristic technology demands materials exhibiting multifunctional properties. Keeping this in mind, an in-depth investigation and comparison of the dielectric, ferroelectric, piezoelectric, energy storage, electrocaloric, and piezocatalytic properties have been carried out on Ba 0.92 Ca 0.08 Zr 0.09 Ti 0.91 O 3 (BCZT) and Ba 0.92 Ca 0.08 Sn 0.09 Ti 0.91 O 3 (BCST) lead-free compounds synthesized through the conventional solid state reaction method. Further, the Rietveld refinement against the XRD patterns affirmed the coexistence of orthorhombic (Amm2) and tetragonal (P4mm) phases at room temperature for both compounds. While BCZT compound demonstrated remarkable dielectric, piezoelectric, and piezocatalytic characteristics with maximum dielectric constant ( ε m ) ≈ 13304 near the Curie temperature (T c ≈ 105 °C), converse piezoelectric coefficient (d 33 ∗) ≈ 609 p.m. V−1, power density (P d) ≈ 89.71 kW cm−3 at room temperature, and 82.7 % Rhodamine B (RhB) dye degradation capability; on the other hand, BCST compound exceled in superior energy storage density (W r e c ) ≈ 191.8 mJ cm−3 with efficiency η ≈ 73.26 % near room temperature and enhanced electrocaloric properties with adiabatic temperature change (Δ T) ≈ 0.980 K, isothermal entropy change (Δ S) ≈ 1.15 J kg−1K−1 and a higher electrocaloric responsivity (Δ T / Δ E) ≈ 0.49 K mm kV−1. These distinctions arise from the difference in ionic radii, lattice distortion, and the electronic configurations of the dopant ions, leading to a greater polarization change and a lower coercive electric field in the BCST ceramic. The outcome of the present study provides valuable insights for selecting a dopant tailored compound for specific application and underscores the potential of such ceramics in energy storage, piezocatalysis, and the development of advanced solid-state cooling devices for future applications. [ABSTRACT FROM AUTHOR]

Novel low permittivity LaAlGe 2 O 7 ceramics was prepared by a solid-state reaction method, and the relationship between microstructure and microwave properties was revealed. XRD and Rietveld refinement confirmed that the crystal structure of LaAlGe 2 O 7 is monoclinic P 2 1 / c space group. Raman spectroscopy reflects the trend of internal structural order and phonon-damping behavior of LaAlGe 2 O 7 ceramics. The ceramic sintered at 1250 °C exhibited the best surface morphology and optimum microwave dielectric properties of ε r = 9.22, Q × f = 33417 GHz, τ f = −71.68 ppm/°C. The lattice energy and packing fraction are used to explain the change of Q × f value. The relationship between phonon damping behavior and microwave dielectric properties was revealed. The temperature stability was studied by bond valence. The LaAlGe 2 O 7 ceramics is a strong candidate for the substrate material of millimeter wave communication. [ABSTRACT FROM AUTHOR]

Samples in the La 2 MoO 6 – Sm 2 MoO 6 – MoO 3 system were obtained using the solid-state synthesis method. The phase formation in the given compositional section was firstly studied, and the homogeneity region of the fluorite-like lanthanum-samarium molybdate was determined, as confirmed by XRD analysis including Rietveld refinement and SEM with energy-dispersive microanalysis. The fluorite-like phase contains less molybdenum than the isostructural neodymium molybdate Nd 5 Mo 3 O 16+δ. The homogeneity region of fluorite-like solid solutions has been determined, which corresponds to the La 5-x Sm x Mo 2.75 O 15.75 section in the composition range 2.5 ≤ x ≤ 3.5. The crystal structure is characterized by the splitting of cation positions and the presence of excess oxygen in the octahedral voids of the structure. Oxygen atoms in the octahedral positions are displaced from the center of the voids and enter into the molybdenum coordination sphere. The density of single-phase ceramic samples increases with the increase in samarium content. The conductive properties of single-phase ceramics were investigated in an air atmosphere using impedance spectroscopy. The total conductivity was ∼10−2 S cm−1 for La 2.5 Sm 2.5 Mo 2.75 O 15.75 at 800 °C. The grain bulk conductivity exhibits a break at a temperature of approximately 600 °C, which may be explained by the depletion of charge carriers in the structure. [ABSTRACT FROM AUTHOR]

In the present investigation, we report a comparative study of structural, magnetic and electric transport properties in bulk NiFe 2 O 4 and Ni 0.7 Zn 0.3 Fe 2 O 4 ceramics. The materials were synthesized by solid state reaction method. X-ray diffraction analysis confirmed the cubic spinel structure of the ferrite samples belonging to the Fd 3 ‾ m space group. The structural analysis of the ceramics was comprehensively evaluated from Rietveld refinements of the XRD data and Raman studies. An increased grain size in the Ni 0.7 Zn 0.3 Fe 2 O 4 microstructure was noticed due to Zn substitution. Both structural and microstructural modifications led to a significant change in the magnetic and electric properties of the Ni 0.7 Zn 0.3 Fe 2 O 4 ceramic. A large increase in saturation magnetization with decreased coercivity was noticed in the Ni 0.7 Zn 0.3 Fe 2 O 4 system due to Zn substitution. DC resistivity was observed to decrease in the Zn-substituted nickel ferrite ceramic due to increased grain size and larger electron hopping between Fe3+ and Fe2+ ions, as verified by the XPS analysis. Further, a remarkable dielectric relaxation has been observed in the Ni-Zn ferrite owing to greater charge hopping and interfacial polarization. Complex impedance spectra of Ni 0.7 Zn 0.3 Fe 2 O 4 revealed evidence of surface polarization contribution with grain and grain boundary effect on the electric transport properties. [ABSTRACT FROM AUTHOR]

A series of hexagonal perovskite Ba 12 M 0.5 Zr 0.5 Nb 9 O 36 (M = Ni, Mg, Co, Zn) ceramics were prepared by solid-state reaction method. XRD and Rietveld refinement results showed that all ceramic samples belong to the hexagonal perovskite structure with R- 3 m space group. With different B-site ion substitution, variation of permittivity (ε r) can be ascribed to the average ion polarizability. Ceramics with highest relative density exhibit maximum quality factor (Q×f) values. Among all samples, the optimal microwave dielectric properties of ε r = 35.2, Q×f = 57,985 GHz, and τ f = 26.4 ppm/°C for Ba 12 Mg 0.5 Zr 0.5 Nb 9 O 36 were obtained, which indicated that Ba 12 Mg 0.5 Zr 0.5 Nb 9 O 36 ceramic is a candidate material for microwave communication applications. [ABSTRACT FROM AUTHOR]

Vanadium-doped barium hexaferrite with a nanostructure is a highly valuable material in various technological fields, such as electronics, permanent magnets, and sensors. The Ba 1-x Fe 12-x V x O 19 (x = 0, 0.02, 0.04, 0.06, 0.08, and 0.1) nanoparticles derived from the aqueous solutions containing Fe:Ba molar ratio of 10:1 through the sol-gel auto-combustion method. Computational study was also performed using the first-principles density functional theory (DFT) approach. Crystal structure optimization, band structure, and density of states (DOS) calculations were conducted by CASTEP code. The variation of the structural, magnetic, optical, morphological, and electronic properties of V5+-doped barium hexaferrite was investigated. The XRD analysis combined with the Rietveld refinement showed the hexagonal structure of M-type barium ferrite (BaM), confirmed by the FT-IR analysis. The morphology of BaM nanoparticles was studied by the FE-SEM and TEM micrographs. In addition, magnetic and optical properties were analyzed through VSM and UV–Vis analysis. Crystallite size was found to be highly effective in tuning the coercivity and optical band gap of barium hexaferrites, which varied, respectively, from 3.24 to 4.83 kOe, and 2.69–3.69 eV. Magnetic results showed that several variables like cations distribution, lattice strain, and hematite secondary phase affected the nanoparticles' magnetization. The DFT simulation results showed a sharp reduction of electronic band gap energy whether V takes the position of Ba or Fe (from 1.10 eV in undoped to 0.64 and 0.14 eV in doped structures). The projected density of states (PDOS) calculations demonstrated that the d orbitals of V and Ba mainly contribute to the valence band maximum (VBM) and conduction band minimum (CBM), respectively. [ABSTRACT FROM AUTHOR]

Advancing energy density, enabling lithium metal anodes, and ensuring unparalleled safety and operational reliability in lithium batteries hinge on advancing inorganic solid-state electrolytes. To overcome current impediments, we present an innovative approach that integrates glass-ceramics with a pioneering new Nasicon strategy involving molybdenum doping. In the conducted study, a series of 14Li 2 O-9Al 2 O 3 -38TiO 2 -(39-x)P 2 O 5 -xMoO 3 glasses, denoted as LATPMo x , along with their corresponding glass-ceramics (LATPMo x -GC), have exhibited a promising characteristic as solid electrolytes. X-ray diffraction (XRD) analysis confirms the formation of the novel Mo-doped Nasicon phases in the glass-ceramics, as validated by Rietveld refinement. Examination of the crystallization kinetic behavior of the glasses reveals a three-dimensional nucleation process with spherical particle growth, featuring an activation energy of 165 kJ mol−1. Transmission Electron Microscopy TEM characterization aligns crystallization behavior with crystallite and distribution within the glass matrix, resulting in a compact and dense microstructure. The structural properties of the resultant phases are examined through FT-IR, Raman spectroscopy, and TEM-SEAD analysis. Vickers indentation tests were employed to assess the microscopic fracture toughness, and both the glass and glass-ceramics materials demonstrated favorable mechanical performance. Optical characterization using UV–visible absorption highlights the reduction of Mo6+ to Mo5+, likely occupying tetrahedral sites within the crystalline lattice. Impedance spectroscopy measurement showcases the effective promotion of ionic conductivity following Mo doping, reaching a total conductivity value of 5.50 × 10−5 Ω−1 cm−1 along with a high lithium transference number of 0.99 at room temperature for LATPMo 2.6 -GC glass-ceramic. This value is larger than that of many other glass-ceramics as well as that of the well-known lithium phosphorous oxy-nitride LiPON solid electrolyte whose ionic conductivity at RT is around 2 × 10−6 Ω−1 cm−1. [ABSTRACT FROM AUTHOR]

This article investigates the effect of morphology on the thermoelectric properties of nanostructured zinc oxide. Three different samples of nanostructured zinc oxide, named ZnO, ZnO triethanol amine (TEA) and ZnO Calc., were synthesized. ZnO and ZnO TEA samples were synthesized by the chemical precipitation method, while ZnO Calc. sample was prepared by the direct calcination method. The FESEM analysis revealed that ZnO and ZnO Calc. samples have flakes and nanorod-like morphology, respectively, while ZnO TEA has a mixed hexagonal and irregularly shaped morphology. The Rietveld refinement of X-ray diffraction data confirmed that all the prepared samples have a hexagonal wurtzite phase of ZnO with space group P63mc. The energy-dispersive X-ray spectroscopy confirmed the presence of zinc and oxygen in all the synthesized samples. The electrical resistivity and Seebeck coefficient were recorded in the temperature range of 300–950 K. The negative values of the Seebeck coefficient revealed the n-type nature of all the samples. The increase in electrical resistivity with the increase in temperature confirmed that all three prepared ZnO samples show metallic behaviour. The highest Seebeck coefficient of –245 μV K–1 was attained by ZnO nanorods at 950 K, while the lowest Seebeck coefficient of –212 μV K–1 was obtained for ZnO TEA at 950 K. The highest thermoelectric power factor of 2.11 × 10 - 3 W m–1 K–2 was attained by the ZnO Calc. sample at 950 K. The results indicate that the synthesized ZnO Calc. sample with nanorod-like morphology has better thermoelectric performance as compared to flakes and platelets-like morphology. [ABSTRACT FROM AUTHOR]

We investigate the dielectric and impedance spectroscopic investigation of Pr‐doped NASICON type Na3+xZr2−xPrxSi2PO12${\rm Na}_{3+x} {\rm Zr}_{2-x} {\rm Pr}_{x} {\rm Si}_2 {\rm PO}_{12}$ (x=0.05−0.2$x = 0.05 - 0.2$) samples as a function of temperature and frequency. The Rietveld refinement of X‐ray diffraction patterns confirms the monoclinic phase having C2/c space groups for all the samples. The scanning electron microscopy shows the granular‐like structure and energy dispersive X‐ray analysis confirms the desired compositions. The temperature (90–400 K) and frequency (20 Hz–2 MHz) dependence of electric permittivity are explained using Maxwell–Wagner–Sillars (MWS) polarization and space charge polarization mechanisms. The dielectric relaxation shows nearly equal activation energy for all the samples with a non‐Debye type of relaxation in the measured temperature range. The complex impedance analysis shows the presence of broad grain and grain boundary relaxation peaks. The stretched exponent analysis of electric modulus using the Kohlrausch–Williams–Watts (KWW) function further confirms the non‐Debye type of relaxation. Moreover, scaling analysis of the electric modulus shows a similar type of relaxation for all the samples. The ac conductivity data are fitted using modified power law, where the temperature dependence of exponent (s$s$) confirms the correlated barrier hopping (CBH) type conduction for all the samples. Our results indicate that the Pr‐doped NASICON samples are potential candidates for charge storage devices due to their large electric permittivity. [ABSTRACT FROM AUTHOR]

Lead‐based piezo‐ceramics like lead zirconate titanate (PZT) are a mainstay for many piezoelectric applications. However, lead oxide (PbO) evaporation during sintering poses a significant environmental challenge. Flash sintering (FS) is a novel technique that can densify ceramics in seconds and at a much lower furnace temperature. The liquid‐phase FS (LPFS) of PZT (Pb (Zr0.5Ti0.5) O3, with 3 wt.% Cu2O and PbO in the molar ratio of 1:4) is investigated in this work. Further, a comparison has been made among the lead loss, dielectric, and piezoelectric properties of flash‐sintered and conventionally liquid‐phase‐sintered PZT. It has been observed that the evaporation of PbO has been brought down 3–5 times by FS. The dielectric constant of LPFS PZT is significantly higher, especially at higher frequencies with lower dielectric loss. An enhanced piezoelectric coefficient in flash‐sintered PZT has also been observed. The LPFS of PZT shows that the lead loss can be brought down significantly with the added benefit of enhanced dielectric and piezoelectric properties. XRD and Rietveld analysis show an increase in tetragonality after FS in comparison with conventional sintering. XPS and ESR studies show a difference in defect concentration after FS in comparison with conventional sintering that is likely responsible for the enhanced dielectric and piezoelectric properties. [ABSTRACT FROM AUTHOR]

In the present manuscript, zinc oxide nanoparticles (ZnO NPs) were synthesized using a cost-effective and environmentally benign way utilizing Azadirachta indica (neem) leaf extract (AILE). Rietveld refined X-ray diffractogram of biosynthesized ZnO NPs revealed wurtzite-type hexagonal crystallinity with space group P63mc. The optical spectrum of ZnO NPs carried out using ultraviolet visible-diffuse reflectance spectroscopy (UV-DRS) showed an energy band gap of 3.35 eV. FTIR spectrum of the ZnO NPs fabricated via green synthesis route showed a broad anomaly at 3451 cm−1 (hydroxyl group) belonging to phenolic content present in AILE. Microstructural properties were obtained using transmission electron microscopy which showed pseudo-spherical formation of ZnO NPs with an average diameter of particle as 8.5 nm. The TGA-DTA curve of ZnO NPs depicted the thermal stability of synthesized NPs below 405 °C. The study investigated the impact of different parameters, specifically contact time and pH, on the adsorption process on adsorption of Pb2+ using ZnO NPs. It was observed that the adsorption process exhibited a strong dependence on pH. To analyze the kinetics of the process, experimental data was assessed using both the pseudo-first-order and pseudo-second-order kinetic equations. The pseudo-first-order model fit of the data at 100 ppm of Pb2+ concentration gives the R2 = 0.863 with k′ = 2 × 10−2 min−1, respectively, whereas the pseudo-second-order model gives the better fit with R2 = 0.976 which is higher as compared to pseudo-first-order (R2 = 0.863). Additionally, the equilibrium data was modeled using Langmuir and Freundlich isotherm models. The value of the equilibrium constant (K) and R2 value with the Langmuir model were found to be 0.99 and 0.209, respectively, and for the Freundlich model were 3.176 and 0.97, respectively. The experimental results showed good agreement with the Langmuir isotherm model. [ABSTRACT FROM AUTHOR]

BACKGROUND: The degradation of organic pollutants, such as p‐cresol, is a challenge for natural mechanisms, and semiconductors are useful as photocatalysts to restore water quality. This work investigated the effects of neodymium (Nd) and niobium (Nb) doping on the structural and photocatalytic properties of titania (TiO2) under ultraviolet (UV) irradiation. RESULTS: X‐ray diffraction (XRD) results displayed the formation of anatase, TiO2(B) and rutile phases on the Nd/TiO2 and Nb/TiO2 compounds. The Rietveld analysis estimated the composition of phases, as well as the crystal size for each crystalline phase in the samples (<43 nm). The crystal sizes and morphology of the powders were observed using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Energy dispersive spectroscopy (EDS) and X‐ray spectroscopy (XPS) analysis confirmed the presence of Nd and Nb dopants in the TiO2‐based photocatalysts. Nitrogen adsorption/desorption isotherms results revealed pore sizes between 5 and 11 nm, as well as surface area values up to ~81 m2 g−1. The diverse compounds showed excellent removal efficiency of p‐cresol under UV light (10–30% faster than commercial TiO2‐P25). CONCLUSIONS: This synthesis method favored the incorporation of Nd and Nb dopants in the TiO2 structure. Nd/TiO2 specimens showed higher photocatalytic response than Nb/TiO2 samples, possibly as a result of the synergic effects between phases [anatase and TiO2(B)], higher surface area values (≤ ~80.47 m2 g−1), as well as the nature of dopant. Photocatalysts with better photocatalytic performance demonstrated good degradation rate after 20 h. © 2024 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

This paper reports an extensive investigation on the structural, dielectric, ferroelectric and pyroelectric properties of 0.7Ba 1-x Sr x TiO 3 – 0.3Bi 0.5 Na 0.5 TiO 3 (x = 0.0, 0.5, 0.6, 0.7) ceramics synthesized via conventional solid-state reaction (SSR) technique. X-ray diffraction data confirms the presence of pure perovskite phase. The variation of lattice parameters with strontium concentration in 0.7Ba 1-x Sr x TiO 3 – 0.3Bi 0.5 Na 0.5 TiO 3 ceramics were evaluated using the Rietveld refinement of the XRD data. The variation of dielectric permittivity with temperature (ε' ∼ T) shows the diffused phase transition and all the parameters related to the relaxor ferroelectrics (relaxation coefficient, activation energy and freezing temperature) were evaluated. The energy storage properties of the as-prepared ceramics were evaluated using the room temperature PE loop. Amongst the as-prepared ceramics, the composition with x = 0.5 possesses the highest energy storage density of 0.46 J/cm3 with an efficiency of 90 %. The temperature dependent P-E loops were used to study the electrocaloric effect (ECE). The ECE calculations were performed using in-direct method based on Maxwell's thermodynamic relations. A maximum adiabatic temperature change of 0.32 K is achieved at 268 K under a small applied electric field of 25 kV/cm for the ceramic with Sr content x = 0.5. Additionally, electrocaloric responsivity ξ max = 0.13 K mm/kV was also found for the studied ceramics. The above results show that the ceramic 0.7Ba 1-x Sr x TiO 3 – 0.3Bi 0.5 Na 0.5 TiO 3 with the composition x = 0.5 is a viable lead-free option for application in solid state refrigeration. [ABSTRACT FROM AUTHOR]

BaLa 1-x-y MgNbO 6 : xSm3+, yY3+ phosphors were successfully synthesized via high-temperature solid-state reaction method. The crystal structure of representative samples was determined using X-ray diffraction and Rietveld refinement, confirming high phase purity of the prepared phosphors. In the singly doped BaLa 1-x MgNbO 6 : 0.05 S m3+ sample, red emission was observed under 406 nm excitation with an internal quantum efficiency of 27.8 %. The thermal stability at 599 nm (483 K) retained 72.39 % of the emission intensity. To further enhance the luminescent properties, co-doping strategy was employed by substituting Y3+ for La3+ ions. This adjustment significantly improved the brightness of the phosphors. For instance, in BaLa 0.93 MgNbO 6 : 0.05 S m3+, 0.02Y3+, the emission intensity at 599 nm was enhanced by 3.27 times compared to BaLa 0.95 MgNbO 6 : 0.05 S m3+, with an internal quantum efficiency increased from 27.8 % to 60.2 %. Moreover, the color purity of BaLa 1-x-y MgNbO 6 : xSm3+, yY3+ phosphors reached 99 %. Warm white LED devices fabricated using BaLa 0.93 MgNbO 6 : 0.05 S m3+, 0.02Y3+ exhibited a color rendering index (Ra) of 95.7 and a color temperature of 4938K, indicating broad application potential. Experimental results demonstrate that BaLa 0.93 MgNbO 6 : 0.05 S m3+, 0.02Y3+ phosphors with double perovskite structure are a novel and high-performance material for warm white LED phosphors. [ABSTRACT FROM AUTHOR]

In this experiment, we successfully synthesized NaCaY(WO 4) 3 ceramic by employing a traditional solid-state reaction method. Experimental results demonstrated that NaCaY(WO 4) 3 ceramic sintered at 925 °C exhibited excellent microwave dielectric properties with ε r = 10.74, Q × f = 46510 GHz, and τ f = −32.7 ppm/°C. In addition, the dielectric demonstrated excellent chemical compatibility with Ag electrodes, suggesting its potential application in LTCC devices. To address its poor temperature stability, we optimized the original NaCaY(WO 4) 3 ceramic by doping Li 2 CO 3 , ultimately obtaining the Li x Na (1- x) CaY(WO 4) 3 (x = 0∼0.3) ceramics. XRD analysis confirmed the tetragonal scheelite structure of this ceramic systems. Rietveld refinement and Raman spectroscopy analysis revealed that the inclusion of Li 2 CO 3 had no impact on the phase structure of this ceramic system. Furthermore, the P-V-L theory demonstrated that the W-O bond significantly contributed to the Q × f value of Li 0.3 Na 0.7 CaY(WO 4) 3 ceramics. With a sintering temperature of 900 °C, Li 0.3 Na 0.7 CaY(WO 4) 3 ceramics exhibited the optimal microwave dielectric properties of ε r = 11.29, Q × f = 19363 GHz, and τ f = −2.46 ppm/°C. This highly stable microwave dielectric ceramic holds potential for applications in 5G communications. [ABSTRACT FROM AUTHOR]

The polycrystalline Sr 0.8 Sn 0.2 Bi 1.75 Nd 0.25 Nb 2 O 9 (NdSBN) was synthesized using the green synthesis microwave sintering method, which significantly reduced the processing parameters of the NdSBN ceramics. Orthorhombic crystal structure with A2 1 am symmetry was revealed by Rietveld refinement study, whereas the doping-induced strain and crystallite size was studied using the Williamson Hall method. Crossectional SEM micrographs confirm the plate-like structure, with an average grain size of 273.7 nm. A diffuse type of phase transition was observed at 345 °C, which usually arises due to compositional fluctuations and mobile oxygen vacancies; further, the diffusiveness of the NdSBN was studied using Uchino and Nomura function, a modified version of Curie-Weiss law (CW). The frequency and temperature-dependent dielectric study of NdSBN ceramics display a Maxwell-Wagner relaxation with a high loss in a low frequency regime, possibly due to the presence of leakage current in the solid solution. Frequency dependent AC conductivity obeys Jonscher's power law, whereas DC conductivity supports polaron assisted hopping in NdSBN composition with dual activation energies of 0.55 eV and 0.75 eV, which correspond to electrons and ions, respectively. The non-Debye type relaxation mechanism in conjunction with negative temperature coefficient of resistance (NTCR) behavior was demonstrated by temperature dependent impedance spectroscopy, while modulus spectroscopy confirmed the multiple relaxation processes in NdSBN ceramics. [ABSTRACT FROM AUTHOR]

In this study, NaMg 1- x Mn x (PO 3) 3 (0.00 ≤ x ≤ 0.0625) ceramics with low dielectric constant were prepared via the solid-state reaction method. The effects of Mn2+ substitution on the microstructure and dielectric properties (at microwave and terahertz frequencies) of the NaMg(PO 3) 3 ceramics were studied by means of the Rietveld refinement, morphology, and ionic polarizability analysis. It is obtained that the NaMg 0.0975 Mn 0.025 (PO 3) 3 ceramic sintered at 880 °C for 4 h exhibited optimal dielectric properties at microwave frequencies, where ε r = 4.585, Q × f = 48,313 GHz (@17.228 GHz), and τ f = −40.83 ppm/°C. The Q × f and τ f values were changed by 74.2 % and 27.8 %, as compared to the values of 27,728 GHz and −56.52 ppm/°C for the pure NaMg(PO 3) 3 ceramic, respectively. For terahertz frequencies (0.2–1.0 THz), the ε r values were decreased to 3.79–3.98, and the tan δ values were between 0.0203 and 0.1152. All the experimental results indicate that this system exhibits great potentials both at microwave and terahertz frequencies. [ABSTRACT FROM AUTHOR]

NASICON (Na Super Ionic CONductor) type materials are an important class of solid-state electrolytes due to their high ionic conductivity along with decent chemical and electrochemical stability. In this study, a medium-entropy Li 1.5 Zr 1.0 Sn 0.5 Al 0.5 (PO 4) 3 (LZSAP) ceramic electrolyte was prepared via a solid-state synthesis method. Rietveld refinement confirmed the rhombohedral structure of the conventionally sintered sample (LZSAP-CS) at 1000 °C. The spark plasma sintering (SPS) technique was used for the densification of the pellet and resulted in ∼2.64 times higher room temperature conductivity (∼4.42 × 10−5 S cm−1) than that of the LZSAP-CS. The activation energy, calculated in the 30–100 °C range, decreased from 0.37 ± 0.01 eV for LZSAP-CS to 0.31 ± 0.01 eV for spark plasma sintered LZSAP pellet. The transference number of Li+ was ∼0.98, indicating that Li+ is the predominant charge carrier in this electrolyte. Further investigation of the lithium metal-electrolyte interface was conducted using a symmetric Li|LZSAP-SPS|Li cell configuration, demonstrating stability for over 500 h at 5 μA cm−2. LZSAP extends the list of suitable solid-state electrolytes for all-solid-state lithium batteries. [Display omitted] [ABSTRACT FROM AUTHOR]

Powder nanoparticles of ZnO/Fe 2 O 3 composites with varying concentrations of precessour have been synthesized with the help of the co-precipitation method followed by annealing and milling the composite at 700 °C. Then, the obtained powder composites were characterized by X-ray diffraction, Fourier Transformation Infrared spectroscopy, Field Emission Scanning electron microscopy with EDX, Raman spectroscopy, UV–visible absorption spectroscopy, and Photolumnisences. The powder X-ray diffraction results show the formation of the well-crystalline phase of ZnO/Fe 2 O 3. For the further study of the structural analysis, we have done the Rietveld refinement of the XRD data. Williams-hall plot was used to calculate the lattice strain of the composites. Crystalline size, dislocation density, and Rietveld parameters were also calculated using the XRD and Rietveld refinement methods. FESEM study revealed that with an increase in the concentration of Fe 2 O 3 , the shape of the composite changes from spherical to nanosheets via nanorods. The absorption peaks and vibration band obtained at zftir and RAMAN spectra show the formation of the ZnO/Fe 2 O 3. The UV–visible absorption spectroscopy shows the maximum absorption peak in the 200–400 nm range. The successfully synthesized nanocomposites ZnO/Fe 2 O 3 indicate that it can be a potential candidate for organic pollutant degradation. [ABSTRACT FROM AUTHOR]

Wastewater pollution is a pressing environmental issue, necessitating effective remediation strategies to mitigate its impact. This study investigates the use of an efficient catalyst for degrading nitrophenols by converting them into useful aromatic amines, which are crucial building blocks for many pharma industries, and photodegradation of various dyes in their unitary solution as well as in mixture. The Cu-Co-Mn ferrite was synthesized using the sol-gel process and sintered at different temperatures. Structural analysis using XRD and Rietveld refinement revealed a crystal structure corresponding to the Fd 3 ‾ m space group having high purity in all the samples. Additionally, the impact of sintering temperature on the magnetic features of the phases were also studied and the findings suggest that all the phases exhibit ferromagnetic behaviour, which means they can be easily separated from reaction mixtures using an external magnetic field. It was also found that higher sintering temperatures lead to a rise in saturation magnetization and magnetic moment with decrease in coercivity (H c). Further, it was observed that Curie temperature (T c) increases with increase in sintering temperature with the exception of CFM400. The catalytic performance of all the catalysts, including CFM400, CFM500, CFM600, CFM800, and CFM1000, was evaluated and the results indicate that CFM400 exhibits the highest catalytic activity for nitrophenols reduction and photodegradation of dyes, which could be accredited to its larger BET surface area and lower PL intensity. Overall, the structural and magnetic features of the catalyst's sheds light on the underlying mechanisms governing their catalytic activity. These insights offer valuable guidance in the designing and development of effective catalysts for sustainable wastewater treatment practices, emphasizing the importance of considering both structural and magnetic features in catalyst design. [ABSTRACT FROM AUTHOR]

Novel spinel-type Li 2 Mg 2 Ga 2 Ti 3 O 12 ceramics were prepared by the solid-state method. Rietveld refinement revealed that the Li 2 Mg 2 Ga 2 Ti 3 O 12 ceramics possess a cubic spinel structure with the F d 3 ‾ m (227) space group. Raman spectrum analysis indicated that the Q × f and FWHM of ceramics exhibit an inverse relationship. According to the P-V-L theory, the Ti-O bond has the highest percentage of contribution to both of bond ionicity and lattice energy, indicating a significant impact on ε r and Q × f , respectively. The Li 2 Mg 2 Ga 2 Ti 3 O 12 ceramics showed the best microwave dielectric properties (ε r = 15.72, Q × f = 69,633 GHz, and τ f = −20 ppm/°C), sintering at an optimum temperature of 1200 °C. Additionally, a dielectric resonance antenna, on the basis of Li 2 Mg 2 Ga 2 Ti 3 O 12 ceramics was designed and simulated. [ABSTRACT FROM AUTHOR]

This paper presents an investigation into the structural, magnetic, and dielectric characteristics of BaFe12-xYxO19 (x = 0.0, 0.2, 0.4, 0.6) nanoparticles (NPs) produced by the sol-gel method at 800, 900, 1000, 1100 °C annealing. Rietveld refinement analysis shows that the lattice parameter ratio (c/a) lies within the range of 3.93–3.96 provides the confirmation of M type hexaferrite with space group P 6 3 / mmc. The average crystallite size for BaFe 12 O 19 is found to decrease (53.0–23.4 nm) with increasing annealing temperature while for doped BaFe 12-x Y x O 19 it is increased from 30.7 to 96.2 nm. The magnetization found to decrease (82–17 emu/g) with Y3+ content for 800 and 900 °C annealing. However, for 1000 and 1100 °C annealing the magnetization increases and reaches to maximum 100.2 emu/g for x = 0.2 at 1100 °C annealing. The site preference of the Fe3+ ions is responsible to change the value of magnetization. The coercivity of undoped BaFe 12 O 19 varies from 4039 to 2028 with doping content. However, maximum coercivity 4586 Oe is found for x = 0.4 at 900 °C. The dielectric function is found to vary with annealing temperature and Y content as well. The wide range of magnetic properties (soft and hard magnetic) can be used in data storage, spintronic and microwave device applications. [ABSTRACT FROM AUTHOR]

MgO-Nd 2 Zr 2 O 7 (M-NZO) composite ceramics, as a promising material for inert matrix fuel (IMF), can be used to replace mixed oxide (MOX) fuel for consuming plutonium (Pu) storage and minor actinides (MA) in light water reactors (LWRs). In this study, the effect of Y doping and content of MgO on the thermophysical properties and mechanical performances of ω MgO-(1- ω)(Nd 1- x Y x) 2 Zr 2 O 7 (M-NYZ) composite ceramics were systematically investigated. XRD, Rietveld refinement, and SEM-EDS results demonstrated that the as-prepared M-NYZ samples only consist of magnesium oxide and NYZ pyrochlore two phases, and with uniform element distribution and dense microtopography. In terms of properties, the thermal expansion coefficient and the thermal conductivity of 0.5M-0.5NYZ samples at 100–1200 °C is in the range of 13.1 × 10−6 K−1–13.5 × 10−6 K−1 and 3.9 W⋅m−1⋅K−1–15.9 W⋅m−1⋅K−1, respectively. And the Vickers hardness, Young's modulus, and microhardness of typical samples are located in the range of 8.50–10.10 GPa, 183.35–275.32 GPa, and 7.03–10.52 GPa, respectively. Compared with UO 2 fuel, MOX fuel, and other ceramic IMFs, M-NYZ composite ceramics used for IMF exhibit comparable or even superior thermophysical and mechanical properties. [ABSTRACT FROM AUTHOR]

Double perovskites have shown promise in the development of spin polarized conduction and ferromag semiconductors. In this category of double perovskite, we report on the lanthanum ferrocobaltite, co-doped with Pr and Mn. The polycrystalline ceramics were analysed for its structural properties by using Rietveld refinement of X-ray diffraction (XRD) and Raman spectroscopy measurements. The pristine and co-doped samples possess monoclinic structure with P2 1 /n space group. In the pristine compound Co and Fe octahedra are ordered periodically which later gets distorted upon cationic substitution. Scanning electron microscopy (SEM) and energy dispersive spectra (EDS) reveals the grain morphology and elemental analysis. The samples were investigated for their dc and ac electrical responses. The two-probe dc resistance was measured from room temperature RT to 575 K. Dielectric spectroscopy in the RT to 650 K temperature range was performed in the frequency range of 50 kHz to 5 MHz. We observed that introducing Pr at La-site and Mn at Fe site creates structural disorder and tilt in octahedra which results in decreasing the dielectric constant at RT but increases significantly at higher temperature with low dielectric loss. ac conductivity was found to increase with increasing temperature indicating the thermally governed hopping mechanism. All these features validate their potential applications as a high temperature capacitor and can be widely used in automotive and aerospace domains for the storage device application. [ABSTRACT FROM AUTHOR]

In this paper, Ce 2 [Zr 1− x (Cd 1/3 Sb 2/3) x ] 3 (MoO 4) 9 (CZ 1− x (CS) x M, x = 0.01–0.1) were prepared via the conventional solid-state method. XRD and Rietveld refinement analyses confirmed the formation of a single-phase CZ 1− x (CS) x M solid solution with a space group of R -3c(167). The sintering behavior of the samples were investigated using SEM and relative density, which showed that optimal densification for CZ 0.98 (CS) 0.02 M ceramics were achieved at 675 °C with an average grain size of 1.70 μm. The P-V-L theory revealed the significant influence of the Zr(Cd/Sb)-O bond on the dielectric properties of CZ 1− x (CS) x M ceramics. Furthermore, far-IR reflectance spectra indicated that the measured dielectric loss value (1.04 × 10−4) is in line with the calculated value (1.60 × 10−4), suggesting a substantial impact of phonon oscillation absorption on the dielectric properties. Notably, CZ 0.98 (CS) 0.02 M ceramics demonstrated superior performance at 675 °C, with ε r = 10.44, Q × f = 93,152 GHz (at 12.96 GHz), and τ f = −17.73 ppm/°C. [ABSTRACT FROM AUTHOR]

This study examines the use of rice husk ash (RHA) and incinerated sugarcane press mud (ISPM) as precursors in the lime/pozzolan geopolymer system and the effect of the bacterium Lysinibacillus sp. WH on the mechanical properties and microstructures. The RHA-to-ISPM ratio was varied, and the geopolymer pastes were cured at ambient temperature. The results show that an increase of ISPM content up to 5% improves strength and reduces water absorption and voids, while higher ISPM levels beyond 5% degrade the quality of geopolymer paste. An increase in ISPM content reduces setting times due to an increase amount of calcium in the pastes. Notably, the addition of bacteria resulting in a reduction of setting times has been proved for the first time in this work. Moreover, the addition of bacteria can enhance all mechanical properties and introduce self-healing abilities, with microcracks healing within < 20 days of treatment, regardless of mix proportions. Microstructural studies, using a scanning electron microscope (SEM), Fourier Transform Infrared Microscopy (FT-IR), X-ray diffraction (XRD), and Rietveld refinement analysis, reveal that bacteria increase cristobalite, and decrease quartz, thus resulting in strength enhancement of geopolymer pastes. Furthermore, this work is the first to provide evidence that bacteria tend to reduce the efflorescence formation as confirmed by a decrease in gaylussite. These findings pave ways to the production of more sustainable geopolymer systems via upcycling wastes and prolonging service life due to bacterial activity. [ABSTRACT FROM AUTHOR]

Ferrite compounds have gained scientific attention for their multifunctional attributes. This investigation explores the structural, optical, dielectric and conductivity properties of polycrystalline γ-Fe 2 WO 6 synthesized by the solid state route. The X-ray diffraction confirmed the orthorhombic structure and single-phase formation, while the electron microscopy showed uniform distribution of dense micrometer-sized grains in γ-Fe 2 WO 6. The FTIR spectroscopy analysis validated the presence of active stretching and bending modes, signifying oxygen anion vibration at both Fe and W sites. The simultaneous presence of Fe2+ and Fe3+ ions in the matrix, as confirmed by X-ray photoelectron spectroscopy (XPS), results in an augmented optical energy band gap and contributes to dielectric permittivity due to the charge carrier hopping mechanism between the trap sites. The compound manifests semiconductor attributes, evident in its indirect optical band gap measuring 1.7 eV. It is observed that the compound has effectively degraded the Methylene Blue (MB) under the visible light within 40 min with a degradation efficiency up to 63 %. The material's electrical conductivity, follows the Jonscher's power law, signifies its semiconductor nature and adheres to the Small Polaron tunneling model for charge conduction between neighboring sites. The impedance (Z′) curves exhibit dielectric relaxation (≤ 10 kHz) with a similar activation energy to the dc conductivity study. The activation energy, determined from both the impedance and conductivity analyses, indicates a connection with the migration of oxygen vacancies within the material. Our observation reveals the presence of oxygen vacancies, which possibly act as in-gap electron traps, enhancing the correlated optical and ac conductivity properties, making it an appealing material for diverse multifunctional applications. [ABSTRACT FROM AUTHOR]

The present research focuses on the electrical properties of lead-free piezoceramics (0.985- x)(K 0.485 Na 0.485 Li 0.03)(Nb 0.96 Sb 0.04)O 3 -0.015(Bi 0.5 Na 0.5)ZrO 3 - x SnO 2 (KNNLS-BNZ- x SnO 2 , x = 0.003, 0.006, 0.009, 0.012, and 0.015). This study examines the influence of varying SnO 2 doping levels on the microstructure and piezoelectric properties of the ceramics. All the ceramics prepared demonstrate pure perovskite structure without any secondary phases. The Rietveld refinement analysis of XRD data reveals the existence of multiphase evolution around room temperature. The tetragonality (c/a) and cell volume of the ceramics tend to rise with an increase in Sn4+ content, potentially leading to improved ferroelectric characteristics. The optimum values obtained were Curie temperature (T c) = 395 oC, remnant polarization (P r) = 21.07 μC/cm2, piezoelectric coefficient (d 33)=357 pC/N, piezoelectric voltage constant (g 33) = 24 × 10−3 Vm/N, and figure of merit (FOM off) = 10.34 pm2/N, corresponding to the ceramic doped with x = 0.012 SnO 2. The findings indicate that an optimal amount of Sn4+ in the host composition KNNLS-BNZ improves piezoelectric properties by constructing an R-O-T phase boundary near room temperature. This study suggests that the ceramic with x = 0.012 SnO 2 exhibits a favorably high T c coupled with an exceptional energy harvesting capability, making it a suitable candidate for energy harvesting applications. [ABSTRACT FROM AUTHOR]

The objective of this work was to synthesize a new catalyst x-MoO 3 /Ni 0.5 Zn 0.5 Fe 2 O 4 using the combustion reaction method and to evaluate its catalytic potential and reuse in biodiesel production from waste oil, optimizing the process through experimental design. The catalysts were characterized in terms of structure by X-ray diffraction and phase quantification by Rietveld refinement, surface area by the Brunauer-Emmett-Teller technique, experimental density by helium pycnometry, acidity tests by ammonia desorption at programmed temperature, chemical analysis by X-ray fluorescence, morphology by scanning and transmission electron microscopy, and catalytic properties. The products of the simultaneous transesterification and esterification reactions were characterized by gas chromatography and acidity index. The results indicate the formation of catalysts with surface area ranging from 1.5 to 1.7 m2/g and density ranging from 4.5 to 5.1 g/cm3, composed of major crystalline phases of MoO 3 in the orthorhombic configuration and cubic Ni 0.5 Zn 0.5 Fe 2 O 4 ferrite, with total acidity ranging from 70 to 182 μmol/g of NH 3. Morphological characterization revealed that the catalyst comprises irregular plates of various sizes and shapes with a wide range of cluster sizes. In the simultaneous transesterification and esterification reactions of residual oil, the catalysts were active under all conditions tested, with emphasis on the catalyst containing 50 % Mo ions and 50 % Ni 0.5 Zn 0.5 Fe 2 O4 presenting the best catalytic performance with a conversion of 95 % in ethyl esters and a reduction of 71 % in acidity, with a service life of 6 cycles, an average conversion of 90 % and good thermal and structural stability after use. The experimental design was significant and predictive, with a confidence level of 95 %. Statistical analysis identified that all input variables (temperature, time, and amount of catalyst) were significant for the adopted design. The new catalyst composed of molybdenum, iron, nickel, and zinc has a positive impact on biodiesel synthesis from frying oil and ethanol. [ABSTRACT FROM AUTHOR]

This study investigates the effects of chromium inclusion on the structural, microstructural, frequency dependent electrical and magnetic properties of SrTiO3 perovskite. The composition of Sr1−xCrxTiO3 (SCT) ceramics with x = 0.00, 0.02, 0.04 is preapred via a high‐temperature solid‐state reaction route. Rietveld refinement of X‐ray diffraction data revealed a cubic structure with space group Pm3¯m$P m \bar{3} m$. All SCT samples have been analyzed for Cr incorporation at the Sr‐site using Raman and Fourier transform infrared spectroscopy. Field‐emission scanning electron microscopy studies probed a gradual increase in grain size due to the uniform distribution of dopants across sample surfaces, as confirmed by energy‐dispersive X‐ray spectroscopy analysis. Cr doping strongly influences the electrical properties of grain and grain boundary resistance. All samples undergo Arrhenius‐type transport via oxygen ion migration and mixed conduction (ionic/electron), whereas relaxation occurs through mixed‐type association (VO··−TiTi4+2+″$V_{\text{O}}^{\cdot \cdot} - \text{Ti}_{\left(\text{Ti}\right)^{4 &amp;amp;amp;plus;}}^{2 &amp;amp;amp;plus;} ^{&amp;amp;amp;aposx; &amp;amp;amp;aposx;}$) and (2CrSr.−TiTi4+2+″$2 \text{Cr}_{\text{Sr}}^{.} - \text{Ti}_{\left(\text{Ti}\right)^{4 &amp;amp;amp;plus;}}^{2 &amp;amp;amp;plus;} ^{&amp;amp;amp;aposx; &amp;amp;amp;aposx;}$). The magnetic nature of Cr‐doped samples confirms room‐temperature ferromagnetism due to carrier‐associated oxygen vacancies and Ruderman‐Kittel‐Kasuya‐Yosida interaction. These findings investigate Cr doping as mixed‐ionic and electronic conductors for intermediate temperature‐solid oxide fuel cells and spintronics‐based semiconductor devices. [ABSTRACT FROM AUTHOR]

In this work, an attempt is made for improving the piezoelectric properties of a lead-free (Na 0. 5 K 0. 4 8 5 Li 0. 0 1 5) (Nb 0. 9 8 V 0. 0 2) O3 ceramic system by doping manganese in it. The Rietveld analysis of XRD micrographs of the ceramics indicates the samples crystallizing into 99.86% of orthorhombic phase and very small traces of tetragonal phase around room temperature. The Curie temperature ( T c ) is hardly affected by the incorporation of Mn 4 + into the system. At the manganese concentration of 0.02 wt.%, the ceramic system attains the peak values in its density, dielectric constant at room temperature ( ε RT ), planar electromechanical coefficient ( k p) , piezoelectric coefficient ( d 3 3 ), and remnant polarization ( P r ). The optimum piezoelectric properties of k p = 4 3 % and d 3 3 = 1 9 3 pC/N are observed for this composition. The study reveals that the modification of (Na 0. 5 K 0. 4 8 5 Li 0. 0 1 5 ) (Nb 0. 9 8 V 0. 0 2) O3 with an appropriate quantity of Mn 4 + can produce the desired changes in the crystallographic properties and densification so as to eventually improve its piezoelectric properties. [ABSTRACT FROM AUTHOR]

In this study, zinc silicate hybrid scaffolds with hierarchical meso/macroporous structures were synthesized using evaporation-induced self-assembly and sacrificial foamy templates. F127 triblock copolymer and polyurethane (PU) foam served as templates for mesoporosity and macroporosity, respectively. The scaffolds were calcined at 550, 650, and 750 °C for 2 h to remove the templates and form the crystalline phase. Analytical techniques, including BET, XRD, SEM, FTIR, and STA, were used to study the impact of calcination temperature on the scaffolds' meso-texture and crystalline phase. Results showed that increasing the calcination temperature to 750 °C significantly enhanced the overall crystallinity. The crystallized ZnO content increased from 10.3 wt% to 32 wt%, and the willemite (Zn 2 SiO 4) crystalline phase formed. Willemite content was approximately 3 wt% at 650 °C and 67 wt% at 750 °C, as determined by quantitative XRD analyses via Rietveld refinement. The emergence of the willemite phase adversely impacted the specific surface area, leading to a reduction from 123.18 m2/g to 2.18 m2/g, and compromised meso-texture-related characteristics, indicating a substantial disruption in mesoporosity. The pure willemite sample was also obtained by increasing the calcination temperature up to 1000 °C. Although the sample contained no secondary phase, the specific surface area and total mesopore volume were drastically reduced, indicating the negative effect of high calcination temperature on mesoporosity. In contrast to the mesostructure, the macrostructure of the scaffolds exhibited negligible sensitivity to calcination temperature, maintaining a mean macropore diameter of around 200 μm. Furthermore, the in vitro performance of the scaffolds was evaluated by assessing apatite formation ability, degradability, and cytocompatibility. It was demonstrated that the scaffolds calcined at 750 °C exhibited superior performance in terms of apatite formation and cytocompatibility when cultivated with MG-63 human osteosarcoma cells. [ABSTRACT FROM AUTHOR]

An A site disordered rare earth-based perovskite-derived structured new compound is synthesized using low-cost solid-state reaction method. The phase formation of the desired compound is established through the X-ray diffraction technique. Rietveld analysis of the obtained XRD data confirmed that the compound exhibits orthorhombic symmetry with pbnm space group which is further supported through Raman spectroscopic analysis. The surface morphology and microstructure analysis of the synthesized compound is carried out using scanning electron microscopy approach. The optical properties study done through UV–Visible absorption spectroscopy suggests possible application in optoelectronic devices. The frequency and temperature dependence of dielectric properties are studied for the analysis of electric polarisation in the sample. Electrical properties study conducted through complex impedance spectroscopy approach disclosed the dominant contribution of grain to the electrical response of the material with temperature dependent relaxation process in the compound. The effect of temperature on the dc resistance is further analysed to find the suitability of the material for thermistor application. The frequency dependent data of ac conductivity follows Jonscher's power law. The temperature dependent ac conductivity graph was used to estimate the activation energy in order to identify the specific charge species engaged in the ac conduction process. [ABSTRACT FROM AUTHOR]

In the present investigations, Gd3+ ions were substituted at the Sr2+ site through conventional solid state reaction technique. The influence of Gd3+ ion substitution on the physical attributes of Sr2FeTiO6 (SFTO) was meticulously examined. The basic structure of Sr2 − xGdxFeTiO6 (SGFTO) (x = 0.2 to 0.8), was employed to start the Rietveld structural refinement of the powder X-ray diffraction patterns. This process confirmed the presence of a cubic structure with a space group of Pm3m. The replacement of Gd3+ ions, noted for their larger ionic radii, led to a minor increase in the lattice parameters and the volume of the unit cell. The identity of the elements within the compound was determined by examining their oxidation states through X-ray photoelectron spectroscopy. The SEM images reveal that as Gd content increases in the SGFTO samples, the structure becomes denser and more agglomerated, with reduced porosity and less uniform particle sizes. This suggests that higher Gd content leads to a more compact morphology, potentially impacting the material's electrochemical performance and mechanical stability. The use of diffuse reflectance measurements confirmed that the band gap values decreased slightly from 2.95 eV to 2.24 eV for the Sr2 − xGdxFeTiO6 (x = 0.2–0.8) materials, indicating that these synthesized samples exhibit semiconductor nature. The study investigated how often the dielectric constant and its behavior change with temperature, and these measurements proved that as the amount of Gd3+ in the material increased from 0.2 to 0.8, the dielectric constant also increases. The research on magnetization showed that the prepared materials had a stronger magnetic property and displayed a antiferromagnetic behavior. All synthesized materials made in this way has the possibility to be used in today's electronic devices, magneto-optical storage devices, and magneto-dielectric technologies. Highlights: • The study investigates the substitution of Gd3+ ions at the Sr2+ site in Sr2FeTiO6 using the solid-state reaction method, examining its impact on the material's physical properties. • Rietveld refinement of X-ray diffraction patterns confirmed that Sr2-xGdxFeTiO6 (x = 0.2–0.8) maintains a cubic symmetry with a Pm3m space group, with Gd3+ ion substitution causing a slight increase in lattice parameters and unit cell volume. • X-ray photoelectron spectroscopy and EDAX pattern analysis confirmed the presence and uniform distribution of Sr, Gd, Fe, Ti and O elements, indicating a homogeneous and uniform structure. • Diffuse reflectance measurements showed a reduction in band gap values from 2.95 eV to 2.24 eV with increasing Gd3+ substitution, indicating a semiconductor-like nature of the synthesized samples. • Dielectric constant measurements revealed a progressive increase with higher Gd content, while magnetization analysis indicated an enhanced magnetic nature with antiferromagnetic character, highlighting potential applications in electronic technologies, magneto-optical storage systems, and optoelectronic and sensor devices. [ABSTRACT FROM AUTHOR]

Optical characteristics and microstructure of multilayered zirconia with different yttria contents in each layer can be influenced differently with a layer after speed sintering. The layer-wise translucency and opalescence of dental zirconia (E.max, E.max ZirCAD prime; Cercon, Cercon ht ML) after conventional (control) and speed sintering were analyzed using a spectrophotometer (n = 5). Specimens were subjected to microstructural analyses (n = 2) using field-emission scanning electron microscopy (FE-SEM) and phase analyses (n = 1) using high-resolution X-ray diffraction (HRXRD) and Rietveld refinement. The translucency parameter (TP) and opalescence parameter (OP) were analyzed using a 3-way ANOVA, followed by Scheffé's post hoc test (α = 0.05). The average grain size was analyzed using the Welch's t-test and Kruskal–Wallis test, followed by the Bonferroni–Dunn post hoc test (α = 0.05). Changes to the TP and OP after speed sintering were only observed in the dentin layers. Although the TP of E.max increased (p < 0.05), the difference was below the 50:50% perceptibility threshold (ΔE00 = 0.8). The OP of E.max decreased slightly, whereas that of Cercon increased slightly (p < 0.05). The microstructure and phase fraction of both zirconia barely changed. Therefore, speed sintering is considered to have a negligible clinical impact on the optical characteristics and microstructure. [ABSTRACT FROM AUTHOR]

In powder diffraction, lattice symmetry relaxation causes a peak to split into several components which are not resolved if the degree of desymmetrization is small (pseudosymmetry). Here the equations which rule peak splitting are elaborated for the six minimal symmetry transitions, showing that the resulting split peaks are generally broader and asymmetric, and suffer an hkl‐dependent displacement with respect to the high‐symmetry parent peak. These results will be of help in Rietveld refinement of pseudosymmetric structures where an exact interpretation of peak deformation is required. [ABSTRACT FROM AUTHOR]

The structural and luminescence properties of the Lu 3 Al 4 Sc 1 O 12 :Pr and Gd 3 Al 3 Sc 2 O 12 :Pr garnet scintillators co-doped with boron (B3+) ions were investigated. The addition of B3+ and Sc3+ to the structure has a positive effect on the luminescence properties, especially on the photo, radio emission intensities, quantum efficiency, and results in a reduction of the decay time, which is necessary for high-quality scintillators. Structural properties of garnets have been determined after X-ray diffraction analysis coupled with Rietveld refinement. Surface morphology analysis was performed using a scanning electron microscope and particle size was also determined. Elemental composition was confirmed by the ICP-OES technique. Reflection, excitation (in the UV and VUV range), emission (upon excitation by UV or X-rays), decay time, and quantum efficiency at room temperature were measured. Furthermore, the influence of temperature on excitation, emission, and decay curves was also analyzed. The obtained luminescence properties indicated positive effect caused by doping. [Display omitted] [ABSTRACT FROM AUTHOR]

The lattice distortion induced by element doping is regarded as an effective approach to improve the superconductivity of Bi-based superconductors. In this study, a series of Bi 2 Sr 2- x Ca x CuO 6+ δ (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0 and 1.2) ceramic samples are prepared by Pechini sol-gel method. The Ca-doping effects, structural stability and superconductivity of Bi-2201 phase are studied by electron microscopy, high-pressure Raman spectroscopy, the standard four-probe technique, X-ray diffraction and Rietveld refinements. Results indicate that all samples are constituted by Bi-2201 main phase and Ca 8.56 Sr 5.44 Bi 16 O 38 impurity. It can be determined that Ca atoms have entered Bi-2201 orthorhombic lattice and preferentially occupied the Sr-sites. When Ca atoms are introduced and high-pressure is exerted, the Bi-2201 lattice can present a relatively high structural stability. Meanwhile, the correlations between doping amount x , Cu–O–Cu bond angle (θ), carrier concentration of CuO 2 planes and superconducting onset transition temperature (T c,onset) are discussed particularly. It should be noted that the Bi-2201 lattice has the largest θ , the highest carrier concentration and the highest T c,onset value of 84.98 K when x = 0.8. [ABSTRACT FROM AUTHOR]