Search

This research article delves into the synthesis and characterization of Li(1‐x)Sm(x/3)NbO3 ceramic, employing a high‐energy ball milling process. The investigation explores the incorporation of Sm3+ at the Li+1 site across a range of compositions (x = 0, 0.01, 0.02, 0.03, 0.04, 0.05). Structural analysis, using x‐ray diffraction (XRD) and Rietveld structural refinement, establishes that within the investigated composition range, no significant changes in the crystal structure are evident. The x‐ray photoelectron spectroscopy revealed the presence of oxygen vacancies as well as the stable oxidation state of different elements like O2−, Nb5+, Sm3+, and Li1+. At sintering temperature 1050°C, the average grain sizes vary approximately from 1.5 to 3.8 μm for different compositions with regular grain morphology. The UV‐Vis analysis reveals a noteworthy reduction in the band gap to 3.09 eV for the x = 0.01 composition. Photoluminescence studies exhibit distinct green, orange, and red bands, with the highest intensity observed for x = 0.01, showcasing promising optical properties. The dielectric permittivity of Sm‐substituted compositions surpasses the response of pure LiNbO3, demonstrating an increasing trend with temperature in the frequency range 100 Hz‐1 MHz intriguingly, no Curie temperature is observed up to 500°C for any composition. The polarization vs electric field hysteresis loop response highlights better polarization characteristics at the room temperature and maximum polarization is 0.66 μC/cm2 for the composition x = 0.05. The energy storage response of the developed compositions is investigated, which reveals a maximum efficiency of 46.64% for x = 0.04 in Li(1‐x)Sm(x/3)NbO3. The tunable optical properties, enhanced dielectric response, and notable energy efficiency of these high TC ceramics suggest their utility across diverse applications. These findings not only contribute to the understanding of functional ceramic materials but also pave the way for their optimized utilization in advanced technological applications, particularly in energy storage devices under nonambient conditions at high temperatures. [ABSTRACT FROM AUTHOR]

In this paper, an unexplored solid solution (1-x)Bi(Cu1/2Ti1/2)O3-(x)PbTiO3 has been synthesized and characterized for its crystal structure, dielectric and ferroelectric properties aimed at a selected composition, i.e., 0.30 Bi(Cu1/2Ti1/2)O3-0.70PbTiO3. The paper unveils the different synthesis approaches to achieve pure-phase in Pb-based perovskite-structured materials that are prone to produce impurities during synthesis. The Rietveld refinement of the XRD pattern confirms a tetragonal crystal structure (P4mm) of the composition. The ferroelectric properties of the as-prepared composition are also discussed using P-E hysteresis and PUND characteristics. The composition shows a high Tc (480 °C) and low dielectric losses, making it suitable for high-temperature applications. [ABSTRACT FROM AUTHOR]

Exploring the functionalities of materials requires a profound understanding of the crystal structure. In this paper, room temperature crystal structures of a new solid solution (1 − x)Ba(Cu1/3Nb2/3)O3-(x)PbTiO3 have been investigated in the entire compositional span and different crystallographic phases and phase coexistence regions have been discovered. The confirmation of the symmetry of these crystal structures has been done with the help of Rietveld analysis of the high-resolution XRD data. Despite both the end components, Ba(Cu1/3Nb2/3)O3 and PbTiO3, having tetragonal (P4mm) symmetry, new cubic and monoclinic phases have been discovered for the intermediate compositions with multiple phase boundaries. The composition region 0.05 ≤ x ≤ 0.55 exhibits a cubic crystal structure and increasing PbTiO3 concentration to 0.62 results in a unique coexistence of two tetragonal phases with different tetragonalities. This transformation is mediated by coexisting cubic and tetragonal phases, for 0.59 and 0.60. The crystal structure of the solid solution later transforms into coexisting monoclinic and tetragonal phases for a wider compositional span i.e., 0.65 ≤ x ≤ 0.85. This composition region is very fascinating, as two phenomenologically different monoclinic structures have been observed in it. Finally, a tetragonal phase at x = 1 is achieved through the mediation of two coexisting tetragonal phases, for the region 0.85 < x ≤ 0.975. The evolution of different crystallographic structures and the coexisting phases are critically comprehended using the variations in the lattice parameters and unit cell volume. The presence of multiple phase boundaries spread across a wide range of compositions makes this solid solution very intriguing and a viable choice for exploring different properties with compositional tuning. [ABSTRACT FROM AUTHOR]

Results of the room temperature structural studies on (1-x)Bi(Mg1/2Ti1/2)O3-xPbTiO3 ceramics using Rietveld analysis of the powder x-ray diffraction data in the composition range 0.28⩽x⩽0.45 are presented. The morphotropic phase boundary region exhibits coexistence of monoclinic (space group Pm) and tetragonal (space group P4mm) phases in the composition range 0.33⩽x⩽0.40. The structure is nearly single phase monoclinic (space group Pm) in the composition range 0.28⩽x⩽0.32. The structure for the compositions with x⩾0.45 is found to be predominantly tetragonal with space group P4mm. Rietveld refinement of the structure rules out the coexistence of rhombohedral and tetragonal phases in the morphotropic phase boundary region reported by earlier authors. The Rietveld structure analysis for the sample x=.35 calcined at various temperatures reveals that phase fraction of the coexisting phases in the morphotropic phase boundary region varies with grain size. The structural parameters of the two coexisting phases also change slightly with changing grain size. [ABSTRACT FROM AUTHOR]

The present study highlights the effect of Ga3+ and Cu2+ co-doping on the crystal structure, surface morphology and ionic conductivity of ceria ceramics in the system Ce 0.8 Ga 0.2-x Cu x O 2-δ for potential applications as the solid electrolyte material in the intermediate temperature solid oxide fuel cells (IT-SOFCs). Ultrafine Ce 0.8 Ga 0.2-x Cu x O 2-δ (for x = 0, 0.05, 0.1, 0.15, and 0.2) nanopowders were prepared via glycine nitrate auto-combustion method. Phase identification, microstructural, and ionic conductivity of all the ceria ceramics were observed by powder XRD, SEM, TEM, and impedance analyses, respectively. Rietveld structural analysis using powder XRD pattern for all the co-doped systems confirms cubic fluorite type structure having Fm-3m space group, similar to cerium oxide. All these samples were found to have density above 85% after sintering at 1300 °C for 4 h. Raman spectra revealed the oxygen vacancies in all the compositions. Thermal analysis for change in weight and thermal expansion coefficient with temperature were performed by TGA and high temperature XRD measurements, respectively. Thermal expansion coefficient of the developed electrolytes matches with the commonly used electrode materials. The composition Ce 0.8 Ga 0.05 Cu 0·15 O 1.825 was found to demonstrate the maximum ionic conductivity with the least activation energy among all the existing co-doped ceria ceramics. These features make it a promising candidate in the IT-SOFC as the electrolyte material. Image 1 • Structural, Morphological, Electrical Properties Ce 0.8 Ga 0.2-x Cu x O 2-δ Electrolyte. • XRD, SEM, TEM, Raman and impedance analyses of Ce 0.8 Ga 0.2-x Cu x O 2-δ Electrolyte. • Highest ionic conductivity and lowest activation energy in Ce 0.8 Ga 0.05 Cu 0·15 O 1.825 • Optimal CuO precipitate at grain boundaries give additional path for O2− transport. • Low thermal expansion coefficient (11.10 × 10−6 K−1) for Ce 0.8 Ga 0.05 Cu 0·15 O 1.825 [ABSTRACT FROM AUTHOR]

Studies on (1-x)[Bi(Mg 3 / 4 W 1 / 4)O 3 ]-xPbTiO 3 ceramics across morphotropic phase boundary have been done to investigate the crystal structure and structure-property correlations. Rietveld structure refinement reveals that the structure of the morphotropic phase boundary compositions consists of coexisting ordered tetragonal and cubic phases for 0. 55 < x < 0. 72, not reported earlier. The structure is B-site ordered cubic (space group Fm- 3 m) for the compositions with x ≤ 0. 55, B-site ordered tetragonal (space group I 4/ m) for x ≥ 0. 72. The structure gradually transforms into disordered tetragonal phase (space group P 4 mm) for higher concentrations (x) of PbTiO 3. Raman studies also confirm the B-site ordered structure for the compositions close to morphotropic phase boundary. For all the compositions investigated, two peaks are observed in the temperature dependence of the permittivity, originating due to dielectric relaxation and structural transition from tetragonal (I 4/ m) to cubic (Fm- 3 m) phase. A new phase diagram of the solid solution is established. [ABSTRACT FROM AUTHOR]

Highlights • Nd 0.7 Ba 0.3 Mn 1-x Ti x O 3 (0.05 ≤ x ≤ 0.25) manganites were prepared by combustion method. • Nd 0.7 Ba 0.3 Mn 1-x Ti x O 3 crystallize into orthorhombic structure with Imma space group. • Effect of Ti4+ substitution on structural and magnetic properties is investigated. • Substitution of Ti4+ ion reduces ferromagnetic ordering temperature and fraction. • Nd 0.7 Ba 0.3 Mn 1-x Ti x O 3 exhibit first order phase transition in the vicinity of T C. Abstract The polycrystalline Nd 0.7 Ba 0.3 Mn 1-x Ti x O 3 (x = 0.05, 0.15 and 0.25) perovskite manganites have been synthesized using combustion synthesis method followed by single-step calcination process. Rietveld analysis of the X-ray powder diffraction patterns reveals that the samples crystallize in single phase body-centered orthorhombic crystal structure with space group Imma. The lattice parameters and unit cell volume increase exponentially with doping of Ti4+ ions for Nd 0.7 Ba 0.3 Mn 1-x Ti x O 3 (x = 0.05, 0.15 and 0.25). The temperature dependence of magnetization measurements reveal that all samples undergo transition from paramagnetic (PM) to ferromagnetic (FM) phase on cooling below room temperature. The values of Curie temperature (T C), Curie-Weiss temperature (T CW) and experimental effective paramagnetic moment (μ e f f e x p ) decrease exponentially on the doping of Ti4+ ions. The field dependent magnetization measurements reveal coexistence of FM and antiferromagnetic (AFM) states in the low-temperature region. The experimentally observed saturation moment (μ s a t e x p ) of all the samples is lower than the theoretically calculated values and decreases exponentially with doping of Ti4+, due to AFM component in the FM ordering. The negative slope in the low field region of the M2 vs. H/M Arrott-plots for all the samples reveals that Nd 0.7 Ba 0.3 Mn 1-x Ti x O 3 manganites exhibit a first-order magnetic phase transition. The critical exponents β, γ and δ were estimated for Nd 0.7 Ba 0.3 Mn 1-x Ti x O 3 perovskites. [ABSTRACT FROM AUTHOR]

Results of Rietveld analysis of powder neutron diffraction data on 0.75[Pb(Mg1/3Nb2/3)O3]-0.25PbTiO3 (PMN-0.25PT) at room temperature and 80 K are presented. It is shown that the currently believed structural model based on average rhombohedral structure (space group R3m) with local <110> disordered Pb atoms cannot account for the structure of PMN-0.25PT at 80 K. The low temperature structure of PMN-0.25PT is best refined using Cm space group of MB type. It is argued that with decreasing temperature the short-range monoclinic order at 300 K grows into a truly long-range ordered monoclinic structure at 80 K. [ABSTRACT FROM AUTHOR]

Results of Rietveld analysis of powder neutron diffraction data on 0.75[Pb(Mg1/3Nb2/3)O3]-0.25PbTiO3 (PMN-0.25PT) at room temperature and 80 K are presented. It is shown that the currently believed structural model based on average rhombohedral structure (space group R3m) with local <110> disordered Pb atoms cannot account for the structure of PMN-0.25PT at 80 K. The low temperature structure of PMN-0.25PT is best refined using Cm space group of MB type. It is argued that with decreasing temperature the short-range monoclinic order at 300 K grows into a truly long-range ordered monoclinic structure at 80 K. [ABSTRACT FROM AUTHOR]

We present the structural investigation on multiferroic Ba1-xSrxMnO3perovskite manganites with x = 0.50, 0.60, 0.70 and 0.75 synthesized by combustion method. Rietveld refinement of powder X-ray diffraction data reveals the hexagonal structure with space group P63/mmc for all compositions. The unit cell lattice parameters for Ba1-xSrxMnO3decrease monotonically with Sr-substitution on Ba-site. The value of structural tolerance factor decreases from 1.047 for x = 0.50 to 1.018 for x = 0.75. [ABSTRACT FROM PUBLISHER]

We have investigated the effects of Ti-doping at the Mn-site of La 0.6 Ba 0.4 Mn 1–x Ti x O 3–δ (0.02 ≤ x ≤ 0.08) manganites produced via an auto-combustion technique on the structural and magnetic behavior. All of the compositions crystallize into a cubic structure with Pm 3 ‾ m space group as confirmed using Rietveld analysis of the X-ray diffraction data. Unit cell lattice parameter 'a' and volume 'V' increase upon increasing the doping concentration, which revealed that the larger Ti-ions substitute the smaller Mn-ions in the lattice. Temperature-dependent magnetization measurements revealed that all of the compositions undergo a paramagnetic to ferromagnetic transition at the Curie-temperature (T C). The T C decreases non-linearly from 309 to 212 K as the concentration of Ti-ions increases from x = 0.02 to 0.08. An abnormal behavior in the experimental effective paramagnetic moment was observed in La 0.6 Ba 0.4 Mn 1–x Ti x O 3–δ (0.02 ≤ x ≤ 0.08), which increases with the substitution of magnetic Mn-ions by Ti-ions. The experimental paramagnetic moment increases non-linearly from 6.10 to 6.52 μ B. The downturn deviation in the inverse susceptibility from Curie–Weiss law for the sample with x = 0.08 revealed the appearance of a Griffiths phase. The singularity of the dc inverse susceptibility in the Griffiths phase region provided the numerical values of the Griffiths temperature (T G), critical temperature for random ferromagnet (T C R) , and critical exponent (λ GP) to be 310 K, 247.7 K, and 0.95(1), respectively. In the low temperature region, the larger value of the experimental saturation moment compared to the corresponding theoretical values observed for the La 0.6 Ba 0.4 Mn 1–x Ti x O 3–δ manganites indicates the possibility of spin-orbit coupling. Captions: (a) Room-temperature X-ray diffraction patterns, (b) Variation of lattice parameter and unit cell volume as a function of Ti-doping concentration (x), (c) Temperature dependence of ZFC and FC magnetizations curves and (d) Variation of theoretical and experimental saturation moments as a function of Ti-doping concentration (x) for La 0.6 Ba 0.4 Mn 1-x Ti x O 3 - δ (0.02 ≤ x ≤ 0.08) manganites. [Display omitted] • La 0.6 Ba 0.4 Mn 1–x Ti x O 3–δ manganites were prepared by auto-combustion method. • La 0.6 Ba 0.4 Mn 1–x Ti x O 3–δ manganites crystallize into a cubic structure with Pm 3 ‾ m space group. • La 0.6 Ba 0.4 Mn 1–x Ti x O 3–δ manganites exhibit ferromagnetic ordering and T C decreases non-linearly with Ti-concentration. • La 0.6 Ba 0.4 Mn 1–x Ti x O 3–δ manganite with x = 0.08 exhibits Griffiths Phase above room temperature. • La 0.6 Ba 0.4 Mn 1–x Ti x O 3–δ manganites are showing spin-orbit coupling in low temperature region. [ABSTRACT FROM AUTHOR]

In this paper, an unexplored solid solution (1-x)Bi(Cu1/2Ti1/2)O3-(x)PbTiO3 has been synthesized and characterized for its crystal structure, dielectric and ferroelectric properties aimed at a selected composition, i.e., 0.30 Bi(Cu1/2Ti1/2)O3-0.70PbTiO3. The paper unveils the different synthesis approaches to achieve pure-phase in Pb-based perovskite-structured materials that are prone to produce impurities during synthesis. The Rietveld refinement of the XRD pattern confirms a tetragonal crystal structure (P4mm) of the composition. The ferroelectric properties of the as-prepared composition are also discussed using P-E hysteresis and PUND characteristics. The composition shows a high Tc (480 °C) and low dielectric losses, making it suitable for high-temperature applications. [ABSTRACT FROM AUTHOR]

We report here the “incommensurate modulated” phase along with the ferromagnetic character in nanocrystalline Nd0.5Sr0.5MnO3 perovskite. The Rietveld analysis of powder X-ray diffraction data reveals that the structure of nanocrystalline Nd0.5Sr0.5MnO3 ceramic can be described as a modulated phase in the monoclinic structure with space group Pm and lattice parameters am ≈ 2ao, bm ≈ bo, and cm ≈ 3co, where ao, bo, and co correspond to the lattice parameters of the parent orthorhombic structure for the bulk sample at room temperature. Increasing the crystallite size converts the modulated monoclinic structure to an orthorhombic structure with the Imma space group for the bulk Nd0.5Sr0.5MnO3 sample. The magnetic measurements on nanocrystalline samples reveal ferromagnetic behaviour and the absence of charge ordering transition at low temperatures. The nanocrystalline samples also exhibit Griffith phase like behaviour near the paramagnetic to ferromagnetic phase transition. The Powder X-ray diffraction study of bulk Nd0.5Sr0.5MnO3 in the temperature range of 13 K–300 K reveals the transition from the orthorhombic to the monoclinic structure in the P21/m space group with the coexistence of the two phases in a wide temperature range below room temperature. [ABSTRACT FROM AUTHOR]

The size-dependent structural and magnetic properties of nano and bulk samples of 40 ​mol% Ba2+-doped LaMnO 3 (i.e., La 0.6 Ba 0.4 MnO 3) manganite have been investigated in detail. The Rietveld refinement of X-ray diffraction data confirms that nano and bulk La 0.6 Ba 0.4 MnO 3 manganites crystallize into ideal cubic perovskite structure with Pm 3 ¯ m space group. The refined unit cell parameters decrease with increasing calcinations temperature or particle size. The temperature dependent magnetization measurements reveal that both the bulk and nano samples exhibit paramagnetic (PM) to ferromagnetic (FM) phase transition at Curie temperature (T C). A distinct bifurcation between magnetization curves under zero-field cooled (M ZFC) and field-cooled (M FC) measurements reveals the possible existence of frustrated magnetic ordering or spin glass clusters. For nano sample, a sharp downward deviation in inverse susceptibility from Curie-Weiss law is observed, which indicates the existence of Griffiths Phase. The analysis of the field dependent magnetization M(H) curves measured at 10 ​K, in terms of saturation moments, reveals that there is a coupling between spin and orbital magnetic moments, in bulk sample of La 0.6 Ba 0.4 MnO 3 manganite, which can be quenched by reducing particle size of the manganite. According to the Banerjee's criterion, nano sample exhibits first-order magnetic transition and bulk sample shows second-order magnetic transition in the low magnetic field region. (a) A Williamson-Hall plot for nano sample of LBMO-40 manganite, (b) Rietveld fit for bulk sample of LBMO-40 manganite, (c) Temperature dependent M ZFC and M FC curves for nano and bulk samples of LBMO-40 manganite and (d) log 10 t versus log 10 χ-1 plot for the nano sample of LBMO-40 manganite. [Display omitted] • La 0.6 Ba 0.4 MnO 3 manganite exhibits ferromagnetic ordering above room temperature. • Nano La 0.6 Ba 0.4 MnO 3 manganite exhibits Griffiths Phase in the temperature region 315 ​K ​< ​T ​< ​360 ​K. • Bulk La 0.6 Ba 0.4 MnO 3 manganite is showing spin-orbit coupling in low temperature region. • Quenching of spin-orbit coupling can be achieved by reducing particle size of the prepared sample. • In low-field region, order of magnetic transition switches from FOMT to SOMT as particle size changes from nano to bulk. [ABSTRACT FROM AUTHOR]

Abstract: We present here the results of X-ray diffraction (XRD), dielectric and calorimetric studies on lead magnesium tungustate, Pb(Mg0.5W0.5)O3 (PMW) ceramic. It is shown that the low temperature antiferroelectric phase of PMW having orthorhombic structure (space group Pmcn) transforms to paraelectric cubic (space group Fm3m) phase at 281 K. The phase transition is of first order character as confirmed by coexistence of Pmcn and Fm3m phases over wide temperature range ∼50 K. The first order character of phase transition is also revealed by the observation of thermal hysteresis in the real part of dielectric permittivity and calorimetric studies. We do not find any evidence for the additional intermediate phase between antiferroelectric (Pmcn) and paraelectric (Fm3m) phases as reported in the literature. Anomalies in the heat flow and dielectric measurements support the finding of our XRD results and reveals that the phase transition temperature (Tc) is 281 K instead of 312 K reported in the literature. [Copyright &y& Elsevier]

The isovalently substituted lead-free binary solid solution, 0.67(Bi 1-x La x Fe 0.97 Ga 0.03 O 3)-0.33(BaTiO 3) (BF-BT) (x ≤ 0.07), has been synthesized by solid state ceramic method via air quenching sintering. FTIR and XRD along with Rietveld structure refinement confirmed a pure perovskite phase with a pseudocubic structure (space group Pm 3 ‾ m) for developed compositions. SEM revealed a dense microstructure with fine grain size (<1.5 μm) and minimal porosity. XPS analysis reveals predominantly Bi+3 and Fe+3 states, along with oxygen vacancies (V O · ·). Ferroelectric studies demonstrated a maximum remanent polarization (Pr) of 12.3 μC/cm2 and coercive field E C of 30.95 kV/cm for La3+ concentration of x = 0.03. Overall decrement in Pr can be attributed to dipolar defect-induced random fields reducing the activation barrier for domain nucleation. Leakage current measurement reveals improved resistivity (∼108 Ω cm) up to an applied field of 30 kV/cm. Dielectric measurements unveiled two frequency-dependent anomalies in temperature dependence above room temperature, indicative of diffuse phase transitions. The Vogel-Fulcher model depicted an increasing freezing temperature (from 465 K for x = 0.01–551 K for x = 0.07) and decreasing activation energy (from ∼0.61 eV to 0.07 eV) with increasing La3+ concentration. The estimated diffuseness parameter around ∼2 suggested relaxor behavior. Doping with La resulted in increased dielectric permittivity at 10 kHz (from 4100 to 24066), showcasing the efficacy of site engineering in augmenting the functional properties of BF-BT for high-temperature dielectric and transducer applications. The polarization (P-E) hysteresis loops for compositions La1, La3, La5, and La7, illustrating changes in remanent polarization with increasing La content in Fig (a). Fig (b) highlights current (I-E) curves, indicating peak shifts and current density variations with doping levels. Fig (c) plot elucidates the diffuseness parameter (γ) from the modified Curie-Weiss law, showing an increase in diffuseness with La concentration, where γ values range from 1.72 to 1.99, suggesting relaxor ferroelectric behavior. Fig (d) demonstrates a significant enhancement in dielectric constant at 10 kHz, which increases dramatically from 5000 to nearly 25,000 as La concentration increases, emphasizing the material's suitability for high-temperature applications. Together, these results emphasize the tunability of electrical characteristics through isovalent doping, vital for applications in high-performance electronic materials. [Display omitted] • Lead-free BF-BT relaxors synthesized via air quenching with pure perovskite phase. • Enhanced resistivity (∼108 Ωcm) at higher applied field of 30 kV/cm. • Ferroelectric studies show decreasing remanent polarization with increasing La3+ concentration. • Frequency dispersion suggests relaxor-like behavior due to La+3 ion introduction. • Enhanced dielectric permittivity (∼24066 at 10 kHz) with increasing La+3 concentration. [ABSTRACT FROM AUTHOR]

Temperature dependent structural changes in a nearly pure monoclinic phase composition (x=0.525) of Pb(ZrxTi1-x)O3 (PZT) have been investigated using Rietveld analysis of high-resolution synchrotron powder x-ray diffraction data and correlated with changes in the dielectric constant and planar electromechanical coupling coefficient. Our results show that the intrinsic piezoelectric response of the tetragonal phase of PZT is higher than that of the monoclinic phase. It is also shown that the high piezoelectric response of PZT may be linked with an anomalous softening of the elastic modulus (1/S11E) of the tetragonal compositions closest to the morphotropic phase boundary. [ABSTRACT FROM AUTHOR]

Results of Rietveld analysis of the synchrotron x-ray diffraction data on Pb(ZrxTi1-x)O3 (PZT) for 0.525≤x≤0.60 are presented to show the absence of rhombohedral phase on the Zr-rich side of the morphotropic phase boundary. Our results reveal that the structure of PZT is monoclinic in the Cm space group for 0.525≤x≤0.60. The nature of the monoclinic distortion changes from pseudotetragonal for 0.525≤x≤0.54 to pseudo-rhombohedral for x>0.54 [ABSTRACT FROM AUTHOR]

The understanding of structure-property co-relations is a key to utilising the materials for their best performances. This paper focuses on the physical property characterization of a new binary solid solution series with formula (1-x)Ba(Cu 1/3 Nb 2/3)O 3 -xPbTiO 3. A unique type of crystal structure evolution as a function of composition has been observed for this solid solution series, where a two-phase coexistence is observed in a very large span of compositions at room temperatures. The microstructure, piezoelectric, ferroelectric and dielectric properties along with their entanglement with crystal structure, have been investigated in detail. The compositional homogeneity of selected compositions has been verified with EDS and XPS. The higher responses in the physical properties have been observed near morphotropic phase boundary compositions. On heating above room temperature, peaks in dielectric permittivity responses have been observed that correspond to the phase transitions of non-centrosymmetric phases. The solid solution's best piezoelectric and ferroelectric responses are observed for the x = 0.70 composition showing higher densification, larger grain size and low dielectric losses, and lies near the morphotropic phase boundary region. The solid solution has enormous potential in piezoelectric industries as it possesses morphotropic phase boundary and high-temperature piezoelectricity. Fig. (a) Room temperature XRD pattern of (111), (200) and (220) reflection of (1-x)Ba(Cu 1/3 Nb 2/3)O 3 -(x)PbTiO 3 ceramics sintered at 1050°C for composition x = 0, 0.20, 0.40, 0.59, 0.60, 0.65, 0.70, 0.95 and 1. Fig. (b) P-E hysteresis loop of (1-x)Ba(Cu 1/3 Nb 2/3)O 3 -(x)PbTiO 3 ceramic for composition x = 0.70, 0.85, 0.90 and 0.95 at 50 Hz at room temperature. [Display omitted] • The comprehensive dielectric, ferroelectric and piezoelectric studies were done for (1-x)Ba(Cu 1/3 Nb 2/3)O 3 -(x)PbTiO 3 ceramics. • The solid solution studied exhibit multiple phase boundaries where high responses of physical properties can be found. • Profound correlations of the solid msolution's physical properties have been established with crystal and microstructure. [ABSTRACT FROM AUTHOR]

• Nanoparticles of La 3 Ni 2 NbO 9 have been synthesized using the glycine-nitrate combustion technique. • La 3 Ni 2 NbO 9 crystallizes into a single phase of monoclinic crystal structure with P 2 1 / n space group. • La 3 Ni 2 NbO 9 undergoes PM to AFM phase transition close to 43 K and AFM to spin glass transition near 31.45 K. • In the low-temperature region, nanoparticles of La 3 Ni 2 NbO 9 follow Vogel-Fulcher and dynamic scaling power laws. The nanoparticles of La 3 Ni 2 NbO 9 (LNNO) have been produced via the glycine-nitrate combustion technique followed by a process of calcination with an average crystallite size of ∼ 25 nm. The powder X-ray diffraction (XRD) pattern was analyzed for structure analysis by Rietveld structure refinement. Study on the XRD pattern reveals that LNNO crystallizes in the single phase of monoclinic crystal structure with P 2 1 / n space group. Analysis of temperature-dependent magnetization reveals that nanoparticles of LNNO undergo paramagnetic to antiferromagnetic phase transition at Neel temperature T N ∼ 43 K and antiferromagnetic to spin glass transition at T g ∼ 31.45 K. Analysis of magnetic ac-susceptibility reveals that the LNNO nanoparticles follow Vogel-Fulcher and dynamic scaling power laws in the low-temperature region. [ABSTRACT FROM AUTHOR]

Electrochemical water splitting by use of suitable electrocatalysts is an important process to establish water as sustainable energy material. Similarly, the Oxygen reduction reaction is an important step involved in fuel cells. Hence, suitable catalysts are required for low-cost and high-performance activity towards both processes. In this work, we synthesized Cobalt-free Lanthanum-based double Perovskites oxides La 0.5 Sr 0.5 Fe 0.8 Cu 0.2 O 3 and La 0.5 Sr 0.5 Fe 0.8 Zn 0.2 O 3 by sol-gel method followed by calcination at different temperatures (800 °C, 900 °C and 1000 °C). Prepared double Perovskite oxide materials exhibit bifunctional catalytic activity towards both oxygen evolution reaction and oxygen reduction reaction. Calcination temperatures and composition have a significant impact on catalytic performance because of morphological control along with tuning of surface composition. Powder X-ray diffraction study has been performed to characterize the materials and phases/composition of materials was further analyzed by Rietveld refinement. The morphology of the best catalyst was analyzed by SEM, EDS mapping and XPS analysis. The catalytic performances of the catalysts were examined using electrochemical methods such as linear sweep voltammetry, cyclic voltammetry and electrochemical impedance spectroscopy in 0.1 M KOH solution. Preparation of noble-metal/cobalt-free catalysts is important finding towards establishing water as potential source for hydrogen production. • Cobalt-free catalyst of Lanthanum based double perovskites oxides were synthesized and characterized. • Characterization of prepared catalysts was done by SEM, PXRD and XPS analysis. • The atomic and electronic structures of these compounds can be controlled due to compositional differences, which results in high conductivity. • Prepared catalysts were used as bifunctional electrocatalysts in OER and ORR. • Prepared catalysts exhibit bifunctional catalytic activity towards both OER and ORR in an alkaline media. [ABSTRACT FROM AUTHOR]

Abstract: We have carried out the powder X-ray diffraction and dielectric studies on multiferroic particulate composite xNi0.9Zn0.1Fe2O4/(1− x)PbZr0.52Ti0.48O3 with x =0.15, 0.30, 0.45, 0.60, 0.75 and 0.90 to explore the structural and ferroelectric properties. A conventional double sintering method was used to prepare the xNi0.9Zn0.1Fe2O4/(1− x)PbZr0.52Ti0.48O3 composites. The structure of one of the component Ni0.9Zn0.1Fe2O4 is spinel cubic with space group , while the other component PbZr0.52Ti0.48O3 is selected around the morphotropic phase boundary region in which the tetragonal and monoclinic phases with space group P4mm and Cm coexist respectively. We have carried out Rietveld refinement of the structure to check the formation of ideal composites with separate ferroelectric and ferrite phases. Even though the structural characterization does not reveal the formation of any new phase due to reaction between the two components of the composite during sintering, the tetragonality of the PbZr0.52Ti0.48O3 continuously decreases with increasing the ferrite fraction while the lattice parameter of ferrite phase increases with increasing fraction of the ferroelectric phase. Similarly, the dielectric study reveals clear shift in the ferroelectric to paraelectric phase transition temperature of PbZr0.52Ti0.48O3 during composite formation suggesting that part of Ni2+, Zn2+/Fe3+ ions are diffusing at the B-site of PbZr0.52Ti0.48O3 replacing Ti4+, which in turn decreases its transition temperature. Scanning electron micrograph of sintered pellet surface confirms the presence of two types of particle morphology in the particulate composite, corresponding to ferrite and ferroelectric phases. [Copyright &y& Elsevier]

• Nd 0.5 Ba 0.5 CoO 3 crystallizes into coexisting orthorhombic and tetragonal crystal structures. • Nd 0.5 Ba 0.5 CoO 3 undergoes PM to FM transition at T C ~ 147 K for H = 200 Oe. • Value of T C decreases with increasing applied cooling magnetic field. • Nd 0.5 Ba 0.5 CoO 3 shows PM to FM transition below 150 K and FM to AFM below 20 K transition. • Nd 0.5 Ba 0.5 CoO 3 exhibits Griffiths like phase in the range 147 K ≤ T ≤ 235 K for H = 200 Oe. • Bulk Nd 0.5 Ba 0.5 CoO 3 displays insulator to metal transition at 349 K (76 °C). We have investigated in detail the structural, magnetic, and dielectric properties of half-doped Nd 0.5 Ba 0.5 CoO 3 perovskite cobaltite synthesized by the auto-combustion method. The Rietveld structure refinement from X-ray diffraction pattern reveals that a polycrystalline sample of Nd 0.5 Ba 0.5 CoO 3 crystallizes into an orthorhombically distorted crystal structure with space group Pmmm along with a minor distorted tetragonal phase with P 4/ mmm space group. The temperature dependence of magnetization measurements show paramagnetic to ferromagnetic phase transition at Curie temperature T C around 147 K for H = 200 Oe. The value of T C strongly depends on the applied magnetic bias field, and T C decreases with an increasing magnetic field. The polycrystalline sample of Nd 0.5 Ba 0.5 CoO 3 cobaltite exhibits Griffiths' phase in the temperature range 147 K ≤ T ≤ 235 K for H = 200 Oe. Investigation of the isothermal magnetic field measurements on Nd 0.5 Ba 0.5 CoO 3 reveals that it exhibit antiferromagnetic, ferromagnetic and paramagnetic behaviors, at T = 2 K, 100 K and 150 K, respectively. The negative slope of the isothermal Arrott's plots (i.e., H/M versus M2) in the low magnetic field region suggests a first-order magnetic phase transition while the positive slope in high magnetic field region reveals a second-order magnetic transition. The dielectric constant and electrical resistivity of the synthesized Nd 0.5 Ba 0.5 CoO 3 cobaltite material decrease with increasing temperature as well as frequency. Bulk Nd 0.5 Ba 0.5 CoO 3 cobaltite shows insulator/semiconductor to metal transition at 76 °C. [ABSTRACT FROM AUTHOR]

Multiferroic particulate composites have been fabricated by taking the morphotropic phase boundary composition of ferroelectric phase Bi(Ni 1/2 Ti 1/2)O 3 –PbTiO 3 and magnetic phase (Ni,Zn)Fe 2 O 4. The ferroelectric phase has coexisting monoclinic and tetragonal perovskite structures with space group Pm and P 4 mm , respectively whereas the magnetic phase has spinel cubic structure with space group Fd 3 ‾ m. Rietveld structural analysis for the each components of composite reveals that the tetragonality (c/a) of the ferroelectric phase continuously increases with increasing the concentration of magnetic phase and finally transform in rhombohedral (R 3 ‾ c) phase suggesting partial ionic diffusion between ferroelectric and magnetic phases. Composition dependent Mössbauer spectra of (1-x)Bi(Ni 1/2 Ti 1/2)O 3 –PbTiO 3 /x(Ni,Zn)Fe 2 O 4 reveals the superparamagnetic like behavior for the ferroelectric rich composition with x = 0.2. The magnetic ordering increases for the composition with x = 0.4 and 0.6 which completely transforms into ferrimagnetic for the composition with x = 0.9. Unlike the ferroelectric or magnetic components that do not exhibit the magnetoelectric response separately, significant value of magnetoelectric coefficient (> 30 mV/Oe-cm) in (1-x)Bi(Ni 1/2 Ti 1/2)O 3 –PbTiO 3 /xNi 0.6 Zn 0.4 Fe 2 O 4 composite makes it promising for multifunctional applications. [ABSTRACT FROM AUTHOR]

The structures of the recently reported ordered perovskites SrLa(FeTi)O 6 and BaLa(FeTi)O 6 have been revisited using Rietveld analysis of the powder x-ray diffraction data. Our studies clearly show that earlier authors have incorrectly reported the tetragonal structure in the I4/m space group for SrLa(FeTi)O 6 and the cubic structure in the Fm 3 ¯ m space group for BaLa(FeTi)O 6 . The correct structure is found to be orthorhombic in the Pnma space group for SrLa(FeTi)O 6 while cubic in the Pm 3 ¯ m space group for BaLa(FeTi)O 6 . Thus the BaLa(FeTi)O 6 is not an ordered double perovskite as the occupancies of Ba/La ions at A-site and Fe/Ti ions at B-site are disordered resulting in the primitive cubic unit cell in the Pm 3 ¯ m space group. Similarly, the occupancies of Sr/La ions at A-site and Fe/Ti ions at B-site are disordered in SrLa(FeTi)O 6 also, ruling out the ordered perovskite structure. [ABSTRACT FROM AUTHOR]

The structures of the morphotropic phase and the phase coexistence region have been investigated in (1-x)Bi(Mg1/2Zr1/2)O3-xPbTiO3 ceramics. The structure is cubic with space group Pm3m for the compositions with x<0.57 and tetragonal with space group P4mm for the compositions with x>0.59. For the compositions with 0.56

In this paper, we have studied the structural, optical, dielectric and magnetic properties of Eu3+, Bi3+ co-doped LaVO 4 phosphors prepared by solid state reaction method. Rietveld structural analysis of the samples confirms the monoclinic crystal structure with P 2 1 / n space group. The particles size of Eu3+ doped LaVO 4 phosphor increased in presence of Bi3+ ion. The excitation spectrum of Eu3+, Bi3+ co-doped LaVO 4 phosphor reveals bands due to charge transfer state (CTS) and electronic transitions of Eu3+ and Bi3+ ions. The Eu3+ doped LaVO 4 phosphor gives intense red emission centred at 613 nm due to 5D 0 → 7F 2 transition of Eu3+ ion excited at 266, 355 and 394 nm wavelengths. When Bi3+ and Eu3+ ions are co-doped in the LaVO 4 phosphor the photoluminescence intensity is enhanced upto two times. The photoluminescence intensity is largest for the 266 nm excitation. This is due to energy transfer from CTS and (1P 1 , 3P 1) levels of the Bi3+ ion to 5D 4 level of the Eu3+ ion and increase in the particles size of phosphor. The Eu3+, Bi3+ co-doped LaVO 4 phosphors also show excellent dielectric and magnetic properties with a variation in frequency and magnetic field, respectively. Thus, the Eu3+, Bi3+ co-doped LaVO 4 phosphor may be useful in fabricating displays devices, red emitting phosphors, dielectric capacitors and magnetic devices. Unlabelled Image • The Eu3+, Bi3+ co-doped LaVO 4 phosphors were prepared by solid state reaction method. • The Eu3+ doped phosphor gives intense red emission at 613 nm upon 266, 355 and 394 nm excitations. • The PL intensity of Eu3+ doped phosphor is enhanced upto two times via Bi3+ doping. • This is due to energy transfer from host and Bi3+ ion to Eu3+ ion. • The Eu3+, Bi3+ co-doped phosphors show dielectric and magnetic properties. [ABSTRACT FROM AUTHOR]

Perovskite oxide powders of Nd 1-x Ba x Co 1-y (Fe, Ti) y O 3-δ (0 ≤ x ​≤ ​0.3, y ​= ​0, 0.2) were synthesized by combustion technique and investigated as cathode materials for SOFCs application. The Rietveld refinement of the XRD data confirms the formation of single phase orthorhombic perovskite structure of Pbnm space group within the compositions (0 ​≤ ​x ​≤ ​0.1, y ​= ​0, 0.2). The microstructural studies revealed the grains generated are irregular in shape and non uniform in size in the micrometer range. The X-ray photoelectron spectroscopy (XPS) analysis confirms the presence of mixed valence states of Co3+/Co4+, Fe3+/Fe4+, Ti4+/Ti3+ and O-Lattice/O-Chemisorbed/O-physisorbed species. The measured average CTE values are varies from 18–25 ​× ​10−6 ​K−1 in the temperature range 200–900 ​°C for all the synthesized samples. The electrical conductivity values are found to be 252 Scm−1, 308 Scm−1, 157 Scm−1 at 700 ​°C for the compositions Nd 0.9 Ba 0·1 CoO 3-δ (NBC 0.1), Nd 0.9 Ba 0·1 Co 0·8 Fe 0·2 O 3-δ (NBCFO), Nd 0.9 Ba 0·1 Co 0·8 Ti 0·2 O 3-δ (NBCTO), respectively. XRD analysis reveals no chemical reactivity for the compositions NBCFO, NBCTO with 20 ​mol% gadolinium doped ceria oxide (Ce 0.8 Gd 0.2 O 2−δ) electrolyte material after firing at 1200 ​°C for 8 ​h. The area specific resistances (ASR) were calculated for the symmetrical cells and are found to be 0.67 ​Ω ​cm2, 1.07 ​Ω ​cm2 at 850 ​°C for the NBCFO, NBCTO compositions, respectively. Among the compositions evaluated Nd 0.9 Ba 0·1 Co 0·8 Fe 0·2 O 3-δ showed highest total electrical conductivity ~308 Scm−1 and lowest ASR value ~0.67 Ωcm2 compared to all other compositions. Hence the result suggests the synthesized Nd 0.9 Ba 0·1 Co 0·8 Fe 0·2 O 3-δ composition could be a promising cathode material for SOFCs application. Image 1 • Phase pure novel perovskite oxide compositions of Nd 1-x Ba x Co y (Fe, Ti) 1-y O 3-δ (0 ​≤ ​x ​≤ ​0.3, y ​= ​0, 0.2) were synthesized by combustion method. • Reactivity of synthesized perovskite oxide powders with Ce 0.8 Gd 0.2 O 2−δ electrolyte material was investigated. • A novel Nd 0.9 Ba 0·1 Co 0·8 Fe 0·2 O 3-δ perovskite oxide composition could be a promising candidate as alternative cathode material for SOFCs application. [ABSTRACT FROM AUTHOR]