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The paper analyzes the influence of hard and soft admixture on the functional properties of multiferroic ceramic composites. Two composite materials via solid-state reaction route were obtained. PZT-type materials (with hard or soft admixture) were selected as the ferroelectric component (90%), and nickel–zinc ferrite as the magnetic component (10%). The influence of the doping type (soft and hard admixture of the ferroelectric composite component) on multiferroic composites' dielectric, ferroelectric, electromechanical, magnetic, and magnetoelectric properties were analyzed. Microstructural studies revealed the microstructure of composites with the correct distribution of the magnetic component in the ferroelectric matrix, suitable for maintaining both the ferroelectric and magnetic properties of composite materials. Research has shown that using a ferroelectric component as the PZT (from the morphotropic region and doped with the ferroelectrically soft niobium admixture) shows many advantages, positively influencing the functional properties of the multiferroic composite. It ensures effective polarization of the composite sample, obtaining a high magnetoelectric effect, which is required in sensors or magnetoelectric converters. PZT with a hard admixture shows higher stability of physical parameters, but its characteristic property also hinders the effective polarization of the composite sample. [ABSTRACT FROM AUTHOR]

This paper reports on the structural, optical and luminescence studies of Dy3+–Eu3+ co-doped glass ceramics that are obtained via thermal treatment method. The initial confirmation on glass ceramics with the formation of NaBSiO4 crystalline phase was made through XRD study. The FTIR study showed the vibrations of network formers (B2O3, SiO2) and other functional groups. The quantity of non-bridging oxygens (NBOs) are increased in the glass ceramics with increase in annealing temperature. The absorption spectra (UV–visible-NIR) showed the possible transitions of Dy3+ and Eu3+ ions in the glass ceramics. A red-shift in the absorption band-edge and reduction in the optical band gap values were obtained for glass ceramics owing to their heating temperatures. Photoluminescence studies showed the excitations of Dy3+ and Eu3+ ions under 575 nm and 613 nm emission wavelengths. The obtained NaBSiO4 crystalline phase in the glass ceramics has enhanced the luminescence intensity, and lifetimes of Dy3+ and Eu3+ ions compared to unheated precursor glass when excited under 350 nm and 393 nm. Color chromaticity diagram and correlated color temperature (CCT) values showed a shift in the color of light from warm white of precursor glass to neutral white of glass ceramics. The overall results justify the possibility of considering the Dy3+-Eu3+ co-doped glass ceramics as efficient materials for solid-state lighting applications like W-LEDs. [ABSTRACT FROM AUTHOR]

In this paper, the multi-phase ceramic composites, consisting of dielectric barium titanate BaTiO3 (BTO) and rare-earth-doped magnetic spinel ferrite NiFe2–xSmxO4 (NFSO) with x = 0.00, 0.10, and 0.20 were synthesized through solid-state route. The structure of the prepared samples has been examined through XRD. The results indicate the occurrence of both perovskite (BaTiO3) and spinel (NiFe2–xSmxO4) phases in the prepared composites.The magnetic as well as dielectric properties of the prepared samples were investigated and P–E hysteresis loops were recorded at various voltages. It has been found that the higher Sm concentration composite exhibits high dielectric permittivity (~ 9200) along with high remnant polarization (0.54 μC/cm2) and low saturation magnetization (12 emu/g) at room temperature. The analysis showed that the ferrite phase (NFS0) has influenced the magnetic properties and dielectric response of BaTiO3 material. [ABSTRACT FROM AUTHOR]

The present paper reports the effect of Yttrium substitution on the structural, microstructure, dielectric, ferroelectric, and electrocaloric (EC) properties of the lead-free (Na0.5 Bi0.5)0.94 Ba0.06TiO3 (abbreviated as NBT-6BT) ceramics. For a small quantity of Yttrium (x = 0.01 and 0.05), the X-ray diffraction and Raman spectra exhibit the coexistence of rhombohedral and tetragonal phases at room temperature. However, with x = 0.08 composition, a structural change to pseudo-cubic phase was identified. By adding a small amount of Yttrium, the ferroelectric properties were improved by increasing the remnant polarization from (Pr = 27µC/cm2) for x = 0 up to (Pr = 36µC/cm2) for x = 0.01. This resulted in an improvement of 30% in the estimated ferroelectric parameters as well as an improvement in the piezoelectric properties, as measured by the value of d33 of 130 pC/N. The electrocaloric temperature change (ΔT) is calculated by a direct method using Differential Scanning Calorimetry (DSC) to be at more than 1 K at 5 kV/mm for x = 0.01. Despite the minimal amount employed, our observations lead us to say that the introduction of Yttrium into the NBT-6BT ceramic has directly affected the properties of this material. Nevertheless, with a higher content of Yttrium (x = 0.08), a sudden decrease of both ferroelectric and EC effect was observed. The declined properties at higher contents may originate from the structural change which can influence the polar distribution in the structure. [ABSTRACT FROM AUTHOR]

In this paper, nanocrystalline Nd[(Zn0.925Co0.075)1/2Ti1/2]O3 (NZCT75) powders were synthesized through glycine–nitrate combustion method with the intent of reducing the sintering temperature and improving the microwave dielectric properties of NZCT75 ceramics. Phase composition, structure, and morphology of the powders were analyzed by thermogravimetric analysis–differential thermal analysis (TG–DTA), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The XRD results showed that the as-synthesized powder after rapid self-propagating combustion was highly crystallized and was mainly composed of NZCT75 phase and small amount of unknown phase. The unknown phase could be vanished through the calcination process of 600 °C. Compared to solid-state reaction route, a reduction of about 600 °C in the synthesis temperature for pure phase NZCT75 was realized. A large amount of pores with inhomogeneous distribution in size and shape was found from the SEM image of the as-synthesized powder due to the rapid combustion reaction between glycine and nitrates. The TEM study revealed that the average particle size of the calcined powder is around 31.9 nm. The bulk sample prepared by the nanosized powder could be sintered to 98.8% of the theoretical density at 1250 °C, reducing about 160 °C more than the solid-state reaction method. Meanwhile, excellent microwave dielectric properties of NZCT75 ceramics presented a dielectric constant of 37.17, a quality factor of 257,600 GHz, and a temperature coefficient of resonant frequency of – 29.48 ppm/oC. This study develops a facile approach to synthesize nanocrystalline powder for a promising application in microwave dielectric ceramics. [ABSTRACT FROM AUTHOR]

The partial substitution of Sb5+ on the Ti site for giant dielectric constant material CaCu3Ti4O12 (CCTO) has been done in the present paper, and the effect of Sb substitution on the microstructural, dielectric and electrical property of the material is investigated. The main objective of this paper is to minimize high loss tangent (tan δ) which has restricted the practical applications of CCTO. XRD analysis carried out on the as-synthesized powders confirms formation of single phase material accompanied by dopant-induced lattice constant shrinkage. Scanning electron microscope images demonstrate that the grain size of sintered ceramic samples decreases with the increasing Sb content. The dielectric response of sintered CaCu3Ti4−xSbxO12 samples studied by precision LCR meter suggests that Sb doping is an effective way for maintaining a high dielectric constant and low loss over a broad range in temperature and frequency. Room temperature complex impedance spectroscopy analysis suggests that all compounds are electrically heterogeneous consisting of semiconducting grains and insulating grain boundaries establishing internal barrier layer capacitance model. These results indicate that Sb-doped CCTO ceramics have a favorable prospect to be able to stimulate practical applications. [ABSTRACT FROM AUTHOR]

Although severe lattice distortion is one of the core effects of multicomponent materials, accurate quantitative description is still an open issue. In this paper, density functional theory (DFT) calculations based on special quasi-random structure (SQS) are used to investigate the lattice distortion of multicomponent (TiZrHf)C and (TiZrHf)N ceramics, and the influences on structural, mechanical, electronic and thermodynamic properties. The distortion in (TiZrHf)C and (TiZrHf)N is quantified by the average atomic displacement and the bond length distribution. Our results show that the distortion in (TiZrHf)N is greater than in (TiZrHf)C. Lattice distortion can improve thermodynamic stability while enhancing ductility at the expense of strength and hardness. Moreover, the influence of lattice distortion on thermal properties is further studied, suggesting that the distortion increases the vibrational entropy due to the high-temperature softening of the lattice, thereby increasing the total entropy and thermodynamic stability of ceramics. After distortion, the thermal expansion coefficient is obviously larger and the heat capacity CV and CP also increase, especially at low temperatures. Therefore, the present study is valuable for understanding and optimization of the comprehensive properties of multicomponent ceramics by tuning the lattice distortion effect. [ABSTRACT FROM AUTHOR]

In this paper, series of perovskites ceramics (CaTiO3, BaTiO3–SrTiO3) added with 1.0 wt.% of tin oxide SnO2 were fabricated through the solid-state reaction process. The different specimens' structural and functional groups examinations were investigated by using X-ray and Fourier transform infrared spectrophotometer (FTIR) techniques. The surface morphology and elemental composition were examined by scanning electron microscope (SEM) with energy dispersive X-ray analysis (EDX). The XRD peaks of CaTiO3 and BaTiO3–SrTiO3 were indexed to the orthorhombic and cubic perovskites, respectively. The inclusion of tin oxide into the prepared ceramics caused shifting in the position of the peaks towards higher angles resulting in deformation in the crystal structure of the ceramics. FTIR results confirmed the formation of the desired compositions. The average grain size increased upon the addition of ton oxide into CaTiO3 and BaTiO3–SrTiO3 ceramics. In addition, the radiation shielding performances were examined. The results showed that the addition of SnO2 to the CaTiO3 and BaTiO3–SrTiO3 ceramics enhances the shielding properties of these ceramics. The linear attenuation coefficient (LAC) at a gamma photon energy of 0.015 MeV enhanced from 72.186 to 73.115 cm−1 when the SnO2 increase from 0 to 1 wt.% for samples CTO and CTO@SnO2, respectively. In this regard, the LAC coefficient of BTO–STO is 168.813 cm−1, and it is enhanced by adding 1 wt.% of SnO2 to be 171.004 cm−1 for sample BTO–STO@SnO2. The results also illustrate a decrease in the ceramics half-value layer and the gamma-ray transmission factor with the addition of the SnO2 in the ceramic matrix. The results obtained validate the possibility of applying the manufactured ceramics for radiation protection purposes. [ABSTRACT FROM AUTHOR]

The fluorescent ceramic GdAG:Ce was formed by aqueous tape casting-isostatic pressing process and synthesized by high temperature solid state method. To investigate the effect of introduction of Gd3+ on the crystal structure, the photoluminescence (PL) properties, decay lifetime and the white light-emitting diodes (WLED) applications, non-Gd3+ analogue sample YAG:Ce was prepared as well. In contrast, fluorescent ceramic GdAG:Ce exhibited a relatively smaller XRD peaks, much stronger PL emission intensity and shorter lifetime than that of YAG:Ce. These findings could be beneficial to the improvement of the WLED performance. Moreover, fluorescent ceramic GdAG:Ce was made up of practical with garnet structure, which possessed good thermal stability. As a consequence, an increase of color rendering index (Ra) to 62.3 and decrease of correlated temperature (CCT) to 3208 K was achieved by the WLED device based on fluorescent ceramic GdAG:Ce. The impressive results provided a basis for the fluorescent ceramic used in the field of WLED with high Ra and low CCT. [ABSTRACT FROM AUTHOR]

Lithium tantalite (LiTaO3) is an excellent single crystal, only a few studies focused on polycrystalline LiTaO3 ceramics, because it is difficult to sintering densification in fabrication process by common sintering. In this paper, LiTaO3 composite ceramics with added 3 wt% MnO2 were obtained by hot-pressing sintering at different temperatures from 1200 to 1350 °C. The sinterability, microstructure and dielectric properties of LiTaO3 ceramics fabricated at sintering temperatures were investigated. The relative density of the LiTaO3 ceramics was significantly enhanced as the sintering temperature increases first and then decreased. The LiTaO3 ceramics achieved the highest relative density (98.6%) and shown homogeneous microstructure when sintered at 1300 °C. The LiTaO3 and manganese oxide phases were observed in the MnO2/LiTaO3 ceramics fabricated at different sintering temperatures. The dielectric properties of MnO2/LiTaO3 ceramics were significantly influenced by the sintering temperatures. The study of dielectric properties revealed that the specimen had excellent dielectric properties when sintering temperature was 1300 °C and the dielectric constant was 78, as it tends to stay invariable at room temperature. [ABSTRACT FROM AUTHOR]

In this paper, Co0.5Zn0.5FeCrO4/Ba0.85Ca0.15Zr0.1Ti0.9O3 (CZFC/BCZT) composite ceramics with mass ratios (1:1, 3:1, 5:1, and 7:1) were prepared by solid-solution reaction method combined with sol–gel method. Effects of mass ratios on the microstructure, magnetic, dielectric, and ferroelectric properties were investigated. The CZFC and BCZT phase is verified without any secondary phases by XRD. SEM is used to distinguish the microstructure of CZFC / BCZT composite ceramics, which reveals the porous- and homogeneous structures of specimens. The permittivity of CZFC/BCZT ceramics is strongly dependent on its composition and decreases with the increase of CZFC content. Saturated polarization (Ps) and remnant polarization (Pr) of CZFC / BCZT composite ceramics gradually decline with increasing CZFC content from 1:1 to 5:1. The Ps and Pr values of CZFC / BCZT ceramics increase abnormally at 7:1 due to the larger leakage current caused by the pore. Magnetic properties, including Mr (remnant magnetization), and Ms (saturation magnetization), increase with the increase of CZFC content. The largest Mr (0.67 emu/g) and Ms (0.015 emu/g) are obtained at 7:1. [ABSTRACT FROM AUTHOR]

While the emergence of pottery manufacturing is a wide-spread historical occurrence, and one that has garnered the attention of archaeologists for decades, we know very little about how these ancient vessels were created. Through the application of radiographic scanning and computed tomography this paper provides insights into the manufacturing techniques used by the earliest potters in North America. While x-rays have been used to investigate ceramic manufacturing techniques for decades, this paper provides a reassessment of radiography in light of advances in both computed tomography and reconstructive software. [ABSTRACT FROM AUTHOR]

Lustres are a kind of ceramics from the Mediterranean basin dating from Middle Age and Renaissance times that display astonishing colorimetric properties: their colour changes with respect to the direction under which they are observed. These properties are related with the structure containing nanoparticles of noble metal produced by the potters. In fact, various effects play a role in the aspect of these ceramics: plasmon absorption, interferences and diffusion. Interferences occur in the specular direction, as is commonly seen, but also in diffuse directions. In this paper, a model able to simulate these interferential effects in the diffuse directions is developed in order to understand the optical properties of the lustres. The model integrates all the phenomena mentioned above and leads to good results in reproducing the colour effects observed. The results obtained here give some clues in order to understand the reasons that may have pushed the potters to improve and control the difficult process they were using at that time to produce those ceramics. [ABSTRACT FROM AUTHOR]

In the present paper, Pb(Mg1/3Nb2/3)O3 (PMN) ceramics prepared by the columbite method were investigated. The dielectric study indicates typical relaxor properties, with a frequency dispersion in the range of 200–350 K. The relaxor-to-paraelectric phase transition was evidenced by the continuous decrease of the local order parameter derived from the permittivity-temperature data. As a result of the critical behavior, the main Raman modes show anomalies at: (i) ∼150 K; (ii) ∼220 K (i.e. close to the critical temperature reported for the field-induced ferroelectric state in PMN single crystal); (iii) ∼260 K (i.e. the temperature of the permittivity maximum); (iv) ∼350 K (the temperature for initiation of the cluster freezing process T*); (v) ∼620 K (Burns temperature). The frequency split of the doublet at ∼605 and ∼500 cm−1 presents a critical behavior related to the local symmetry lowering and to the structure ordering due to a phase transformation which takes place below T*. The tunability in the paraelectric state was interpreted in terms of reorientation of the non-interacting nanopolar clusters in a double-well potential. The temperature dependence of the nanopolar domain size also shows anomalies in the range of T*. The size and dynamics of the polar nanodomains is essential in determining the functional properties of the Pb(Mg1/3Nb2/3)O3 relaxor. [ABSTRACT FROM AUTHOR]

This paper deals with Ca and Zr co-doped BaTiO (BCTZ) ( x = 0.1, 0.13, 0.2 and y = 0.05, 0.1, 0.15). These ceramics were prepared using the conventional solid state method. The symmetry, dielectric properties, Raman spectroscopy, ferroelectric behavior and piezoelectric effect were examined. X-ray diffraction (XRD) results display that morphotropic boundary occurs from tetragonal to orthorhombic region of BCZT and polymorphic phase transitions from tetragonal to orthorhombic, orthorhombic to rhombohedral regions of BCZT. The evolution of the Raman spectra was investigated as a function of compositions at room temperature, in correlation with XRD analysis and dielectric measurements. We note that the substitution of Ca in Ba site and Zr ions in Ti site slightly decreased the cubic-tetragonal temperature transition ( T ) and increased the orthorhombic-tetragonal ( T ) and rhombohedral-orthorhombic ( T ) temperatures transitions. The ferroelectric properties were examined by a P- E hysteresis loop. The two parameters Δ T and Δ T are defined as Δ T = T − T and Δ T = T − T , they come close to T for x = 0.13, y = 0.1, which reveals that this composition is around the polymorphic phase. The excellent piezoelectric coefficient of d = 288 pC N, the electromechanical coupling factor k = 40%, high constant dielectric 9105, coercive field E = 0.32 (KV mm) and remanent polarization P = 0.1 (µc mm) were obtained for composition x = 0.13, y = 0.1. [ABSTRACT FROM AUTHOR]

The red glaze (slip) that characterizes the Terra Sigillata potteries, greatly contributed to their success during the Roman period. This feature can in fact be partially explained by the microstructure (crystalline phases and grain sizes) and the physico-chemistry (compositions) of the ceramics. In this paper, we describe how the technique of synchrotron micro scanning X-raydiffraction could contribute to the understanding of the elaboration process and origins of these ceramics. The small (micron) size of the X-raybeam coupled with the use of a sample scanning stage allows one to spatially resolve the distribution and other characteristics of the constitutive mineral phases. [ABSTRACT FROM AUTHOR]

This paper presents a new functional material for smart structure applications. Piezoelectric PZT/cement 1-3 composites that have good compatibility with civil engineering structural materials have been studied. The composites with different volume fractions of PZT ranging from 0.25 to 0.77 were fabricated by the dice-and-fill method. It was found that the 1-3 composites have good piezoelectric properties that agreed quite well with theoretical modeling. The thickness electromechanical coupling coefficient could reach 0.55 in the composite with a ceramic volume fraction of 0.25. Those composites have potential to be used as sensors in civil structure health monitoring systems. [ABSTRACT FROM AUTHOR]

In electronic device fabrication, we frequently encounter the situations to deposit thin films of semiconductors, ceramics, and metals sequentially. Since the appropriate methods for depositing these films are frequently different, it should be beneficial for the research of new devices to develop a system that enables the depositions of different films not only sequentially but also in parallel by the procedure as prescribed. In this paper, we report on a tandem system composed of a pulsed laser deposition (PLD) and two plasma chemical vapor deposition (PCVD) chambers and its application in the fabrication of a prototype structure directed towards the field effect a-Si:H solar cell. PLD and PCVD were used to deposit conductive and semiconductive/insulative film layers, respectively. An exchangeable masking scheme was designed and installed in the system so we could make several device structures in parallel and quickly optimize the device and process parameters by the combinatorial methodology. [ABSTRACT FROM AUTHOR]

Raman micro/macro spectroscopy allows a non-destructive remote analysis: body and glaze, crystalline and amorphous phases can be identified, including the nanosized pigments coloring the glaze. Last-generation instruments are portable, which allows examination in museums, on archaeological sites, etc. This paper gives an overview of the potential of the Raman-spectrometry technique to analyze ancient ceramics and glasses. Selected glasses as well as glazes of various porcelains, celadons, faiences and potteries, representative of the different production technologies used in the Ancient, European, Mediterranean, Islamic and Asian worlds, were studied. Their identification is based on the study of the Raman fingerprint of crystalline and glassy phases. Raman parameters allow for the classification as a function of composition and/or processing temperature. Special attention is given to the spectra of amorphous and coloring phases (pigments). [ABSTRACT FROM AUTHOR]

From antiquity, glazes have been one of the techniques used for decorating ceramics. Potters took advantage of the optical properties of these glazes to improve the quality of the object, especially to obtain an appearance or some characteristics that had commercial success. This is why it is important to know the reasons of the visual appearance of glazes. In this paper we present some aspects of the characterization of lustre, one of the on-glaze decorations that results in a more spectacular visual effect, as a microstructure, its composition, its raw materials and some technological aspects of its production. Lustre is a three-dimensional heterogeneous structure, where copper and silver nanoparticles play the most important role, but also alkali elements in the glaze and other components of raw lustre pigments. Lustre properties are determined by copper and silver composition and by distribution and dimension of these metallic nanocrystals in the decoration layer. [ABSTRACT FROM AUTHOR]

Using the solid-state reaction process, we prepared (Bi,Pb)2Sr2Ca2Cu3O10-δ (Bi-2223 for brevity) ceramics with the addition of zirconium dioxide (ZrO2) nanoparticles. The proportion x of ZrO2 per the total masse of superconductor ranged from 0 wt.% to 0.2 wt.%. We report the intragrain critical current density (Jc), pinning mechanisms, and thermal fluctuations induced excess conductivity. Employing numerous characterization techniques, combining X-rays diffraction, electrical transport measurements, scanning and transmission electron microscopes (SEM and TEM), and DC magnetization hysteresis measurements, we find that the ceramic sintered with 0.1 wt.% ZrO2 nanoparticle showed the best superconducting performance. From the analysis of excess conductivity using Aslamazov–Larkin model, we assessed the crossover temperatures between different regimes of conductivity, the penetration depth, the coherence length, as well as the upper and the lower critical magnetic fields (Bc1, Bc2) at zero kelvin for all the ceramics. Critical current density versus temperature deduced from magnetization measurement is raised by NP-ZrO2 addition. Thereby, NP-ZrO2 strengthened the role of δl pinning cores and enhanced the flux pinning ability. [ABSTRACT FROM AUTHOR]

The praseodymium Pr3+ doped at Bi site of Ba0.1Bi0.9(Ti0.9Zr0.1)0.1Fe0.9O3, under low concentrations (0%, 0.1%, 0.5% and 1% abbreviated as BBTZF0, Pr-BBTZF001, Pr-BBTZF005 and Pr-BBTZF01, respectively) were prepared by the solid-state reaction method. A detailed investigation has been made on structural, microstructural, ferroelectric and dielectric properties of Ba0.1(Bi1−xPrx)0.9(Ti0.9Zr0.1)0.1Fe0.9O3 ceramics. Rietveld refinement fitting revealed that the structure of these ceramics, at room temperature is rhombohedral with space group R3c. The cell volume decreased with increasing Pr-content due to the smaller ionic radius of the Pr. Temperature dependence of the dielectric constant (ε′r) of all prepared ceramics showed anomaly around TN (antiferromagnetic transition temperature); thus suggesting a magneto-electric coupling in these materials. The shift of TN with frequency is attributed to the Maxwell Wagner relaxation rather than the relaxor behavior. The P–E loop study shows the improved ferroelectric behavior and the reduced leakage current density with Pr doping. Moreover, the energy storage properties showed a clear enhancement upon the increase of the Pr concentration. The recoverable energy storage density (Wrec) of 2.75 J cm−3 with energy storage efficiency (η) of 44.52% was achieved for Pr-BBTZF01. [ABSTRACT FROM AUTHOR]

To decrease thermal conductivities of ceramic materials applied to thermal barrier coatings (TBCs), substitutional elements are introduced into ceramic materials through defect engineering. However, predicting what substitutional elements are more efficient for decreasing a given TBC ceramic material's thermal conductivity among potential substitutional elements is still a challenge. In this work, a novel approach for predicting the most efficient substitutional elements is presented. It avoids the experimental trial-and-error method and optimizes computational processes, thus saving computational cost. The core part of the approach is the phonon relaxation time expression for a doped ceramic material, which was obtained through the introduction of random variables in the work. Besides, an application of the expression in combination with software Vienna Ab-initio Simulation Package (VASP) for doped SrZrO 3 with rare earth elements is given. It is found that La and Eu elements most efficiently decrease the thermal conductivity of SrZrO 3 . To validate the correctness of the expression and the model, the thermal conductivities of all doped SrZrO 3 are calculated using Slack method. The doped SrZrO 3 with La and Eu has lower thermal conductivities of 1.2 W/(mK) and 1.3 W/(mK), respectively, compared to doped SrZrO 3 with other rare earth elements. Furthermore, it is found that variation trends of various doped materials' reciprocal relative phonon relaxation time obtained by the expression and reciprocal thermal conductivities obtained by Slack method are the same, which suggests our model and expression are reasonable. [ABSTRACT FROM AUTHOR]

The incorporation of foreign nanostructure oxide phase into the YBa 2 Cu 3 O 7 - d ( Y 123 ) superconductor material is capable of producing trapping sites and upgrading the property of flux pinning (FP). Bulk ceramics with porosity around 19% ± 1% having a nominal composition Y 123 + x Dy 2 O 3 are prepared via the solid-state reaction method. Dy 2 O 3 nanoparticles ( Dy 2 O 3 - NPs ) with an average size of about 20 nm and content x = 0.0, 0.1, 0.2, and 0.5 wt% are considered in this study. The structure, microstructure, magnetic susceptibility, electrical properties, and fluctuation-induced conductivity were investigated in detail. The X-ray diffraction (XRD) patterns showed the existence of YBa 2 Cu 3 O 7 - d with orthorhombic structure as a major phase. The microstructural examination using scanning electron microscope (SEM) and energy-dispersive X-ray (EDX) spectroscopy showed that Dy -rich nano-agglomeration segregated at the grain boundaries or on the surface of Y123 grains. The volume fraction of superconductor grain ( f sg ) and Josephson energy coupling (E j) were extracted from AC susceptibility versus temperature measurements. From log–log plots of the excess conductivity versus, the reduced temperature and using the Aslamazov–Larkin model, we assessed the crossover temperatures between different regimes of conductivity, the effective thickness of the 2D layer system (d), the coherence length ( ξ co ), the penetration depth ( λ o ), the critical current density ( J c (0) ) as well as the upper and the lower critical magnetic fields ( B c2 (0) and ( B c1 (0) ) at zero kelvin for all the ceramics. ξ co and λ o decreased, while J c (0) , B c2 (0) , and B c1 (0) increased with Dy 2 O 3 -NPs addition up to 0.2 wt% results in better flux trapping. The highest values of B c 1 (0) , B c 2 (0) , and J c (0) are found to be equal to 2.6 Tesla, 120.6 Tesla, and 65.64 × 103 A/cm2, respectively. The inclusion of a suitable amount of Dy 2 O 3 -NPs into the YBa 2 Cu 3 O 7 - d superconductor is an encouraging way for developing material with good superconducting performances for practical applications such as the second-generation HTS technologies for power transmission and fault current limiters. [ABSTRACT FROM AUTHOR]

Bi and Li co-doping BaZr0.15Ti0.85O3 ceramics were fabricated by the solid-state method, and investigated the impact on the microstructural, dielectric, ferroelectric and energy storage properties. XRD results show that the structure is perovskite and there is no secondary phase in all samples. SEM pictures indicate that the average grain size significantly decreases as the doping concentration increase. In addition, the phase transition peak is broadened and the Curie temperature shifts towards lower temperature. This phenomenon provides a significant possibility for the application to room temperature, and diffuse phase transition occurs. Moreover, P–E hysteresis loops of all samples demonstrate that remnant polarization and saturated polarization diminish as the doping concentration increases. A high energy storage density of 1.23 J/cm3 is obtained in the doped sample, and the energy storage efficiency is also significantly enhanced compared with the undoped sample. [ABSTRACT FROM AUTHOR]

0.42Pb(Mg0.335Nb0.665)O3–0.26Pb(In0.5Nb0.5)O3–0.32PbTiO3 (PMINT): x % Eu2O3 (x = 0, 1, 1.5, 2 and 2.5) ternary ceramics were prepared using solid-state reaction technique. The powder X-ray diffraction analysis confirmed the diffusion of Eu3+ ions in the PMINT lattice and tetragonal structure in the P4mm space group. The temperature and frequency dependence of dielectric measurement revealed the relaxor such as behaviour and high Curie temperature (Tc ~ 180 °C) achieved for PMINT: 1% Eu ceramic. High remnant polarization (Pr ~ 28.09 µC/cm2) and coercive field (Ec ~ 13.36 kV/cm) were attained for PMINT: 1% Eu and PMINT: 2% Eu samples, respectively. An improved piezoelectric charge coefficient d33 ~ 462 pC/N was found for PMINT: 1.5% Eu. The unipolar strain vs electric field (S–E) hysteresis loops were investigated and the maximum strain Smax = 0.11% for PMINT: 2.5% Eu and the piezoelectric strain coefficient d33* = 387 pm/V for PMINT: 1.5% Eu. This work provides a new way to fabricate Eu-doped PMINT ternary ceramics, both piezoelectric and induced strain properties can be enhanced simultaneously. [ABSTRACT FROM AUTHOR]

In this study, the temperature sensing behaviors of emissions of Stark sublevels in Er3+/Yb3+ codoped lead lanthanum zirconate titanate (PLZT) transparent ceramic were examined. Based on the temperature-dependent upconversion fluorescence spectra excited by 980 nm, the emission intensities of the Stark sublevels 2H11/2(1, 2), 4S3/2(1, 2), and 4F9/2(1, 2, 3) were obtained upon increasing the temperature from 160 to 320 K. All the transitions present strong temperature dependence under the competitive effects of thermal excitation and nonradiative relaxation. The optical temperature sensing properties of 2H11/2/4S3/2(1), 2H11/2/4S3/2(2), 2H11/2/4F9/2(1), 2H11/2/4F9/2(2), and 2H11/2/4F9/2(3) were investigated using the fluorescence intensity ratio (FIR) technique. The largest absolute sensitivity Sa of 142.4 × 10–4 K−1 was obtained based on the FIRs of 2H11/2/4F9/2(1) at 320 K, which is approximately 26 times larger than that of traditionally used thermal coupled levels 2H11/2/4S3/2 in the considered sample. In contrast, the maximum relative sensitivity Sr was 2.21% K−1 at 203 K. A comparison of these results with those of other Er3+/Yb3+ codoped materials reveals that Er3+/Yb3+: PLZT ceramics are a promising thermometer material at low temperatures. Applying FIRs based on the photoluminescence of Stark sublevels is a practical approach to achieving greater thermometric efficiency. [ABSTRACT FROM AUTHOR]

A series of Bi1-xSrxMn2-yTiyO5 ceramics were synthesized via a conventional solid-state reaction method, and their crystal structures and magnetic properties were investigated. The strong correlation between the magnetic behavior and mixed–valence states of the Mn ions was characterized by a vibrating sample magnetometer and XPS measurements. Here, we disclose the equation of band angle, length, and magnetic ground state, which is ascribed to the doping element and concentration. Magnetic characterization reveals that Sr- doped (x = 0.3) ceramics exhibit oxygen vacancy-induced ferromagnetic behaviors, which is understood by the bound magnetic polarons mechanism. To clarify the origin of ferromagnetic behavior in non–magnetic doped ceramics, contrast experiments of temperature-dependent magnetic traits of Ti-doped ceramics were analyzed. Furthermore, the tunable Néel temperature is ascribed to the large effective exchange coupling constant. The significance of this work is that we demonstrate an effective tool for manipulating the antiferromagnetic state and offer practical doping principles. [ABSTRACT FROM AUTHOR]

We reported the effect of Erbium (Er with x = 0.005, 0.01, 0.015, 0.02, 0.025 and 0.03)-substituted Ba0.8Ca0.2Ti0.975(Nb0.5Yb0.5)0.025O3 lead-free ceramics. Structural, dielectric, piezoelectric, ferroelectric and photoluminescence properties of all ceramics were systematically explored. At room temperature, X-ray diffraction (XRD) analysis showed that (Ba0.8Ca0.2)1-xEr2x/3 □ x/3Ti0.975(Nb0.5Yb0.5)0.025O3 samples (Abbreviated as BCTYN-xEr) exhibited a pure tetragonal phase for x ≤ 0.025. However, the composition (x = 0.03) showed the formation of an additional phase. The vibrational study was found to correlate strongly with XRD analysis. The dielectric properties were improved in the composition x = 0.01, where the dielectric constant was increased from 5824 for x = 0 up to 6150 for x = 0.01. The composition (x = 0.005) revealed the optimum properties with a d33 piezoelectric coefficient of 88 pC/N, a kp planar electromechanical coupling factor of 16.9% and a Pr remanent polarization of 9.25 μC/cm2. The photoluminescence (PL) results showed, at 525 nm and 550 nm, two strong green bands. As multifunctional materials, BCTYN-xEr samples represent a great potential in the applications of mechanical–electro-optical coupling and integration devices. [ABSTRACT FROM AUTHOR]

TiO2 ceramics synthesized from the rutile TiO2 powders with a mean size of ~ 0.4 μm were sintered at temperatures ranging from 500 to 1300 °C. The diffraction peaks matched well with the pure rutile phase. Grain growth is an important factor of densification and it becomes significant at 800–1300 °C, suggesting that the sintering process likely moves into the intermediate stage. The density renders a value of 97.5% at 1300 °C and starts to bend suggesting that the sintering is reaching its final stage. A thermostable and wide process window can be achieved for TiO2 specimen sintered at 500–800 °C, and it exhibits an εr of 21.7–28.18.8, a Q × f of 11,700–14,600 GHz, a τf of 383–390 ppm/°C, respectively. Not only did it provide a large positive τf, the rutile-TiO2 also rendered a stable and wide process window, suggesting that the proposed TiO2 ceramic can be a promising candidate for use as a τf compensator for ultra-low-temperature co-fired ceramics (ULTCC) materials and the microwave dielectric properties of ULTCC + TiO2 ceramics may be predictable through the mixing rules. [ABSTRACT FROM AUTHOR]

Magnetoelectric coupling in some special materials among the multiferroics family can provide an extra degree of freedom for the functioning of future multifunctional devices. In this context, here, we report a systematic study of multiferroic, 3-phase, (1−x)[0.7BiFeO3–0.3CoFe2O4]–xPbTiO3 composites (x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5) with magnetically tunned robust magnetoelectric (ME) coupling. These composites were synthesized through sol–gel technique and sintering process. The crystalline phases of rhombohedral BiFeO3, spinel cubic CoFe2O4, and tetragonal PbTiO3 were confirmed by X-ray diffraction analysis. A scanning electron microscope was used to analyze the surface microstructures and an energy-dispersive spectroscopy provided the stoichiometric elemental confirmation. Significantly improved dielectric, magnetic, ferroelectric, and lower ac-leakage behavior were observed. The optimum best dielectric properties, saturation polarization, saturation magnetization, and ME couplings were observed for the 10% PTO (x = 0.1) in the composite series. These properties confirmed that a critical amount of PTO could provide enhanced, magnetically robust polarization, making it an excellent tuning candidate for composite properties and multifunctional devices. [ABSTRACT FROM AUTHOR]

Bismuth silicate with sillenite structure (Bi12SiO20) nanophase was prepared via melt–quenching technique in the Bi2O3–ZnO–SiO2 glass system. The effect of replacement ZnO by Bi2O3 was studied. Their thermal behavior showed the change of glass transition temperature (Tg) from 577 °C in the Bi2O3-free glass to 438 °C in ZnO-free glass. In addition, the crystallization temperatures were not only changed from two to one peak, but also decreased from 927 to 476 °C in the same order. According to the heat treatment regimes, willemite, sillenite, tetragonal Bi2O3, cubic Bi2O3 and traces of ZnO were crystallized with different ratios depending on the change in composition and temperature. Sillenite was enhanced with increase heat treatment temperature and/or Bi2O3 additions. Heat treatment at 650 °C/10 h revealed the best regime, where higher degree of crystallization was achieved. The microstructure at 700 ℃/30 min showed nano-scale oriented parallel rod crystals with hexagonal making at their end, whereas clusters of irregular nano-size crystals was appeared at 650 °C/10 h. Transmission spectra of the glasses in UV–Vis–midIR region were increased with Bi2O3 addition reaching 74% in 100B. Photoluminescence properties of both glasses and their corresponding glass–ceramics showed luminescence nature since the blue and green colors were clearly appeared. Calculation of optical bandgap (Eopt) revealed 3.2–2.19 eV with increasing Bi2O3; these values are located in the semiconducting range. The prepared samples can be utilized in electro-optical instruments, also the high transmission in mid-IR nominate it for IR transmitting windows. [ABSTRACT FROM AUTHOR]

The complex dielectric permittivity of a sintered ceramic tablet consisting of 70.5% BiFeO3, 27.7% Bi2Fe4O9 and 1.8% Bi25FeO40 was analyzed as a function of temperature from – 120 °C to 230 °C in two separate temperature runs. The results reveal a complicated dielectric response with two temperature activated relaxation processes. The first is purely Arrhenius relaxation related to hopping processes between Fe3+ and Fe2+ traps induced by oxygen vacancies at grain boundaries. The second process is more unusual. Its characteristic relaxation time follows a quasi-Vogel–Tammann–Fulcher temperature behavior and from fitting the critical temperature point is estimated at T 0 = 766 K . It is absent in the second temperature run. It can be related to dynamic rearrangements of domain boundaries between different crystallites in the ceramic. The results also reveal a ferroelectric phase transition that decayed with repeated heating cycles of the tablet. The ferroelectric phase transition in pure BiFeO3 is 1098 K, whereas the current results show it at 373 K. The origin of this reduction in the critical temperature of the phase transition is traced to locally induced strains on grain boundaries mainly because of unit cell size mismatch between BiFeO3 and Bi2Fe4O9. [ABSTRACT FROM AUTHOR]

The work presents the main characteristics of the process of ablating silicon nitride ceramics by nanosecond laser pulses. Two types of ceramics are considered—tape cast and gas pressure sintered. Laser processing was performed by a Q-switched Nd:YAG laser system at four wavelengths—266 nm, 355 nm, 532 nm, and 1064 nm. The ablation depth dependences on the laser fluence and number of pulses applied at the different wavelengths are presented and discussed. It is found that increasing the laser fluence at a fixed number of pulses leads to a saturation of the ablation depth for all wavelengths used. Further, laser treatment results in a variety of micro- and nanostructures on the surface of the material. Their characteristics are determined as a function of the processing parameters. The ablation process proceeds via decomposition of the ceramic, as traces of silicon and silicon oxide are found in the processed area. The dependences observed are discussed based on a detailed analysis of the morphological and chemical changes estimated by classical analytical methods, namely, SEM, TEM, XRD, XPS, and Raman spectroscopy. The study presented can serve as a basis for the development of a laser-based processing technique for nitride ceramics and fabrication of Si-based composites. [ABSTRACT FROM AUTHOR]

This paper reports the synthesis of xBaTiO3-(1 − x)NiFe2O4 (where x = 0.8, 0.7, 0.6, 0.5) (BT-NF) ceramic composites by wet chemical route. Phase formation of the individual components and the BT-NF composite was studied using X-ray diffraction technique. Variation of dielectric constant and dielectric loss as a function of frequency (100 Hz to 1 MHz) and temperature (RT to 300 °C) were also investigated. Dielectric constant and dielectric loss were found to increase with an increase in ferrite content. Two peaks were observed in ε vs T curve, the peak in the lower temperature region ~ 120 °C was attributed to ferroelectric to paraelectric transition and the second peak was due to the presence of ferrite phase in the composite. Conduction mechanism in the composites was studied with the help of Cole–Cole plots to understand the grain and grain boundary contribution to conductivity. P–E loops were measured at room temperature which demonstrates that all composite ceramics are ferroelectric and the increase in ferroelectricty in the ceramics was due to space charge and not an intrinsic phenomenon. [ABSTRACT FROM AUTHOR]

The current paper is a complementary dielectric study on the clay-based ceramics (CBC) to investigate the contribution of grain and grain boundaries to the dielectric relaxations. The dielectric measurements were carried out on the ceramic composed of 50 wt.% clay and 50 wt.% nepheline syenite) over wider ranges of frequency and temperature, using the advanced broadband dielectric spectrometer. Dielectric spectra suggested that the temperature has a significant effect on the electrical microstructure of CBC. They show the existence of two relaxation process associated to the grain boundaries (GBs) and grains in low- and high-temperature regions, respectively. The relaxation process associated with grain is more predominating over GBs relaxation over the temperature range studied. Interestingly, we reported an anomaly feature in dielectric behavior of CBC at − 40 °C at which all dielectric properties changed abruptly. [ABSTRACT FROM AUTHOR]

NiCuZn ferrite ceramics with high permeability, low power loss and excellent thermal stability are vital materials for high-frequency power devices. This paper analyzed grains growth and grain-boundary diffusion of Ni0.2Cu0.2Zn0.6Fe2O4 ferrite ceramics at lower temperatures by adding optimized additives. X-ray diffraction reveals that the samples are pure spinel ferrite phase sintered at low temperatures. SEM images indicate that uniform and compact NiCuZn ferrite ceramics were obtained at 920 °C for 4 h, which is very advantageous for low-temperature co-fired ceramic (LTCC) technology. In addition, the ferrite ceramics with higher permeability (~ 411 @ 1 MHz), lower power loss in high frequency (~ 442 kW/m3 @ 7 MHz) and good thermal stability were synthesized by controlling grains growth and grain-boundary diffusion. The results indicate that this ferrite ceramic material is a good candidate for the application of miniaturized power electronics in high frequency. [ABSTRACT FROM AUTHOR]

Ba0.85Ca0.15Ti0.90Sn0.09Zr0.01O3 ceramics were prepared by the conventional solid-state route. The effect of different sintering temperatures (1250 °C, 1350 °C, and 1450 °C) on the structural, dielectric, piezoelectric, and microstructure of the samples was investigated. The ceramics exhibited a tetragonal structure with a space group of P4mm and demonstrated a stable crystal structure despite the different sintering temperatures. The ceramic samples obtained similar Curie temperature, Tc approximately ~ 60 °C. Among all, the sample sintered at 1450 °C showed an improved pellet's relative density with the highest dielectric constant, εr value at Tc of 6615. The sintering effect gives ~ 53% increment on dielectric constant at Tc due to the enhancement of the pellet density from 80.35% (sintered at 1250 °C) up to 91.21% (sintered at 1450 °C). Meanwhile, the sample sintered at 1250 °C obtained the highest piezoelectric constant, d33 value, due to the small grain size of 5.186 µm, which might lead to more 90° domain wall motion. The equivalent circuit analysis shows that the electrical microstructures of the samples were influenced by their ceramic microstructures. The sample sintered at 1450 °C exhibits an excellent fit using two sets of the parallel resistor, R and capacitor, C; R1–C1 (grain) and R2–C2 (grain boundary) elements. However, samples sintered at 1350 °C and 1250 °C required a constant phase element (CPE) to fit the R2–C2 element. [ABSTRACT FROM AUTHOR]

Preparation of Zn/Fe co-doped Co–Mn–Ni–O negative temperature coefficient (NTC) ceramics by solid-phase method. The phase structure of the ceramics was analyzed by X-ray diffractometry. The results show that the increase in Zn/Fe content and the presence of a second phase (NiO) do not affect the stability of the cubic spinel structure. The optimum sintering temperature of 1175 ℃ was determined utilizing a DIL 402C dilatometer, and scanning electron microscopy showed that the ceramics had dense and homogeneous grains, the average grain size of the co-doped Zn/Fe ion specimens is smaller than that of the un-doped Zn/Fe ion specimens. The resistance test showed a B constant of 3237.974 K and a resistivity of 1972.384 Ω cm for the undoped Zn/Fe ions. The B constants for the samples co-doped with Zn/Fe ions ranged from 3044.719 to 3162.881 K and resistivities from 1760.821 to 2067.290 Ω cm. The resistivity of the specimens showed a linear relationship with the inverse of the temperature over the temperature range of − 50 to 100 ℃. [ABSTRACT FROM AUTHOR]

In the present paper, the strontium (Sr)-modified Ca1Cu3Ti4O12 ceramic (further termed as CSCTO) has been fabricated by a conventional cost-effective ceramic route. The prepared sample is characterized to obtain the relationship between the structural and electrical properties in a wide frequency (103-106 Hz) and temperature (25-315 °C) ranges. X-ray diffraction spectra depict a single-phase formation of the compound, crystallized in the cubic system. The dielectric relaxation mechanism and electrical properties of CSCTO have been revealed by studying frequency and temperature dependence of dielectric parameters (εr and tanδ) by dielectric and impedance spectroscopy. The temperature-dependant dielectric constant plots depict that at frequency 1 kHz, the compound has very high dielectric constant (order of 104) and relatively low tangent loss. The occurrence of ultra high dielectric constant of the compound may be due to the space charge polarization, interface and Maxwell-Wagner dielectric relaxation around low frequencies and high-temperature range. The contributions of grains in resistive and capacitive properties of the material can be obtained from the Nyquist plot. It is interesting to note that at room temperature, polarization loop (P ~ E hysteresis loop) of the sintered CSCTO showed lossy behavior. The use of TiO2 and CuO2 nano-sized powders in the starting stage of sample preparation with micron size of CaCO3 and SrCO3 powder promotes the kinetics of quick conventional solid state reaction at a microscopic level, that favors above possible mechanisms. [ABSTRACT FROM AUTHOR]

The lead-free Na 0.5 Bi 0.5 0.94 Ba 0.06 TiO 3 (NBT–6BT) ceramics was fabricated at various sintering temperatures using a conventional solid-state reaction method. The effect of calcination temperature was systematically investigated on the structural properties. The XRD results show that the 850 °C is the best calcination temperature, where the NBT–6BT ceramic had the largest crystallite size with a dense sample, 96% of the theoretical value. However, the density decreased significantly with increasing the calcination temperature above 850 °C due to the secondary phase formation. On the other hand, the effect of sintering temperature was studied on the piezoelectric and ferroelectric properties evolutions. It is found that the optimal ferroelectric and piezoelectric values were obtained at 1150 °C (Pr = 27 µC/cm2, Ec = 3.89 kV/mm and d33 = 110 pC/N). According to these results, we suggest that 850 °C and 1150 °C can be considered as optimal calcination and sintering temperature in NBT–6BT ceramic, respectively. [ABSTRACT FROM AUTHOR]

The combination of nanofluids and micro-texture is an established method to improve the tribological properties of TiC-based ceramics (TC). Due to the limitations of nature and function, the mono-type nanoparticle is limited for improvement in lubrication, heat transfer and other aspects. In this study, a new nanofluid based on magnetic Fe3O4 nanoparticles loaded with multi-walled carbon nanotubes (CNTs) was developed by the co-precipitation method as a lubricant to improve the thermal and tribological properties. Firstly, the surfactant with the best adaptability to Fe3O4@CNTs was selected by a visible spectrophotometer to prepare nanofluids with different volumetric concentrations. Then, the micron-grooves were prepared on the tool surface by laser micromachining technology. The tribological properties and contact angles were measured by the ball-on-disc friction method and angle measurement method, respectively. The results show that compared with the traditional water-based cutting fluid and TC, the contact angle, coefficient of friction, and flashpoint temperature of 0.5 vol% Fe3O4@CNTs nanolubricants and textured TiC-based ceramics (TTC) were reduced by 29.17%, 44.69% and 48.28%. The lubrication and heat dissipation mechanism of Fe3O4@CNTs nanofluids on the surface of TTC were also revealed. [ABSTRACT FROM AUTHOR]

(Zn1-x-yAlxBy)O (x = 0, y = 0, x = 0.02 and y = 0.005, 0.01, 0.02) ceramics have been synthesised via conventional solid-state reaction (SSR) method. Each ceramic formed as a single phase with a dense microstructure. The Seebeck coefficient, power factor, and electrical resistivities were determined for all these ceramics. Very interesting changes have been observed in the thermoelectric properties of ZnO ceramics sintered in the atmosphere of argon gas at 1450 °C via Al and B codoping. The power factor ~6.332 × 10 −4 W K − 2 m−1 and Seebeck's coefficient ~ −89.85 µ V K −1 along with lowest electrical resistivity ~ 1.224 m Ω cm at 700.0 °C was obtained for the composition with y = 0.01, i.e., (Zn0.097Al0.02B0.01)O. [ABSTRACT FROM AUTHOR]