Soukaina Merselmiz, Zouhair Hanani, Said Ben Moumen, Aleksander Matavz, Daoud Mezzane, Nikola Novak, Zahra Abkhar, Lahoucine Hajji, Mbarek Amjoud, Yaovi Gagou, Khalid Hoummada, Dejvid Cresnar, Zdravko Kutnjak, Brigita Rozic
The effects of 2% Zr introduction in Ba0.8Ca0.2TiO3 (BCT) system on its electrical and the electrocaloric properties was investigated.
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Over the past decades, there has been significant interest in new cooling technology based on the electrocaloric effect. The large electrocaloric effect observed in polymeric and inorganic ferroelectric materials made possible development of dielectric cooling devices of a new generation. We report a significant impact of annealing on the electrocaloric effect observed in 12/65/35 PLZT bulk ceramics. The electrocaloric data were obtained by direct measurements. Electrocaloric results confirm the existence of the significant electrocaloric response in this relaxor ferroelectric PLZT composition…
Lead-free ba0.85ca0.15zr0.1ti0.9o3 (bczt) ceramic powders were synthesized using the sol-gel method. to achieve high-energy storage and large electrocaloric effect in bulk ceramics the ceramics thickness was reduced. dielectric, ferroelectric, energy storage, and electrocaloric properties were investigated for bczt ceramic with 400 μm. here, pure crystalline structure and homogenous microstructure were identified by xrd analysis and sem measurements, respectively. the dielectric measurements revealed a maximum dielectric constant associated with ferroelectric-paraelectric phase transition. the…
Structural, dielectric, ferroelectric, energy storage properties, and electrocaloric effect were studied in lead-free ceramic Ba$_{0.95}$Ca$_{0.05}$Ti$_{0.89}$Sn$_{0.11}$O$_3$ (BCTSn) elaborated by sol-gel method. Phase purity structure was confirmed from X-ray data using Rietveld refinement analysis which revealed the coexistence of tetragonal (P4mm) and orthorhombic (Amm2) symmetries at room temperature. Phase transitions were detected by dielectric and differential scanning calorimetry results. Energy storage properties were determined from P-E hysteresis, and the electrocaloric properties …
Lead-free Ba0.85Ca0.15Zr0.10Ti0.90O3 (BCZT) ceramic exhibits excellent dielectric, ferroelectric and piezoelectric properties at the Morphotropic Phase Boundary (MPB). Previously, we demonstrated that the use of the anionic surfactant Sodium Dodecyl Sulfate (SDS, NaC12H25SO4) could enhance the dielectric properties of BCZT ceramic using surfactant-assisted solvothermal processing [1]. In the present study, structural, dielectric, ferroelectric properties, as well as electrocaloric effect and energy storage performances of this BCZT ceramic were thoroughly investigated. X-ray diffraction (XRD) …
Ferroelectric ceramics (Ba0.85Ca0.15)(Ti0.9Zr0.1-xSnx)O3 (x=0.00, 0.02, 0.04, 0.06) were prepared by a sol-gel method. Structural investigation revealed the co-existence of tetragonal (P4mm) and orthorhombic (Pmm2) symmetries at room temperature for the undoped ceramic, while only a tetragonal structure (P4mm) was observed for the doped ceramics. Dielectric measurements indicate a dielectric relaxation process at high temperatures which is essentially related to the hopping of oxygen vacancies. Furthermore, a down shifting of the Curie temperature (TC) with increasing Sn4+ doping rate has been…
The electrocaloric (EC) effect is calculated for Gd-substituted PMN (x = 0 to 0.1) relaxors from temperature dependent heat capacity and polarization measurements, using a thermodynamic Maxwell equation. Polarization change with temperature reveals an anomalous behaviour around the glass transition temperature, which is in the vicinity of a crossover from positive to negative EC effect, which is explained evoking the critical slowing-down of the polar nano-domains dynamics to super-dipolar glass state upon cooling. The maximum negative EC coefficient is observed to decrease from 0.4 K-mm/kV at…
Recent findings of a large electrocaloric (EC) effect in polymeric and inorganic ferroelectric materials open a potential possibility of development of solid-state cooling or heating devices of new generation with better energy efficiency that may be less harmful for the environment. We investigate by using direct measurements, the temperature and electric field dependence of the electrocaloric response in Pb1-xLax(ZryTi1-y)1-x/4O3 bulk ceramics (PLZT) with x=0.06 and 0.12. Here, the properties of the EC response were probed in a part of the PLZT composition phase diagram with low y=0.40 compo…
Lead-free BaTi0.89Sn0.11O3 (BTSn) ceramic was elaborated via a solid-state reaction method and its dielectric, ferroelectric, energy storage, electromechanical as well as electrocaloric properties were investigated at 25 kV/cm. Pure perovskite structure was confirmed by X-ray diffraction analysis. The maximum of the dielectric constant was found to be 17390 at 41 °C. The enhanced total energy density, the recovered energy density, and the energy storage efficiency of 92.7 mJ/cm3, 84.4 mJ/cm3, and 91.04%, respectively, were observed at 60 °C, whereas the highest storage efficiency of 95.87 % wa…
Improvement of the electrocaloric effect and energy storage performances in Pb-free ferroelectric Ba0.9Sr0.1Ti0.9Sn0.1O3 ceramic near room temperature
本研究合成无铅铁电BSTSn陶瓷，在室温20kV/cm电场下实现58.08mJ/cm³可恢复储能密度、84.36%效率及0.63K电热温变，为固态制冷与储能提供高潜力候选材料。
The electrocaloric (EC) effect and energy storage properties of eco-friendly ferroelectric Ba0.9Sr0.1Ti1-xSnxO3 (BSTS-x) ceramics prepared by the conventional solid-state reaction method were studied. Significant energy efficiency exceeding 80% was found in our samples. In particular, BSTS-5 and BSTS-10 samples exhibit 92% and 88% efficiency, respectively, over a wide temperature range around room temperature (RT). Direct EC measurement and an indirect method based on the thermodynamic approach were used to characterize the EC effect, and both yielded consistent results. The largest electrocal…
Stabilization of the first-order phase transition character and Enhancement of the Electrocaloric Effect by NBT substitution in BaTiO$_3$ ceramics
本研究通过NBT取代增强BaTiO$_3$陶瓷的四方形，稳定一级相变并抑制弛豫特性，在x=0.20、40 kV/cm下实现约1.65 K的大电卡效应。
A-site deficient Ba$_{0.975}$La$_{0.017}$(ZrxTi$_{0.95-x}$)Sn$_{0.05}$O$_3$ (x = 0.05; 0.20) ceramics (BLaZ100xTS) were synthesized using the solid-state reaction. The microstructural study revealed a high density and low porosity in the studied ceramics. Besides, grain size lower than 1.5 micrometer was observed in the studied compounds, which is due to the incorporation of the rare earth element (lanthanum). X-ray diffraction and Raman studies revealed that BLaZ5TS and BLaZ20TS crystallize in a perovskite-type structure with tetragonal and cubic symmetry, respectively. The dielectric study s…
Enhancement of the energy storage and electrocaloric effect performances in 0.4 BCZT 0.6 BSTSn medium entropy ceramic prepared by sol gel method
本文通过溶胶-凝胶法设计合成了0.4BCZT 0.6BSTSn中熵陶瓷，在低电场下同时实现高储能密度、高效率和大电卡效应，并具有优异的温度稳定性。
Direct electrocaloric characterization of ceramic films
本文提出了一种结合聚合物基底和快速红外成像的新方法，直接表征陶瓷薄膜的电卡效应，成功捕获了Pb(Mg1/3Nb2/3)O3基薄膜的大部分绝热温度变化，为验证巨电卡效应及加速器件集成提供了新途径。
The Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) ceramics were successfully prepared by sol-gel process, and sintered at 1420 degree. The effect of sintering times (2, 4 and 6 h) on structural, microstructural, electric properties, energy storage, and electrocaloric effect was systematically examined. X-ray diffraction (XRD) results show that all the samples crystallize in the pure perovskite structure. The morphotropic phase transition from the tetragonal to the orthorhombic phase (T-O) was identified and confirmed by Rietveld refinement. The BCZT ceramic sintered at 1420 degree for 4h possesses a good re…
Direct and Indirect methods of electrocaloric effect determination and energy storage calculation in (Na0.8K0.2)0.5Bi0.5TiO3 ceramic
本研究通过直接和间接方法测定了无铅NKBT陶瓷在铁电至非各态历经相变附近的电卡效应与储能性能，实现了1.10 K绝热温度变化和0.78 J/cm3可恢复能量密度。
The Rietveld refinement of the polycrystalline powders of 1% Fe and Mn-doped (Na0.5Bi0.5)0.94Ba0.06Ti0.98V0.02O3 at the Ti-site confirmed a single rhombohedral (R3c) phase. The bandgap, (Eg) was affected by the anti-phase octahedral tilt angle and the spin-orbit splitting energy of Ti4+2p3/2 and Ti4+2p1/2 states. The decrease in Bi loss and increase in the binding energy of Ba due to Fe/Mn doping has been correlated to the strengthening of Bi-O and Ba-O bonds which was revealed from the XPS studies thereby further related to the average A-O bond length from structural studies. Hence, a reducti…
Electrically driven adiabatic changes of temperature are identified in the archetypal electrocaloric material PbSc0.5Ta0.5O3 by comparing isothermal changes of electrical polarization due to slow variation of electric field, and adiabatic changes of electrical polarization due to fast variation of electric field. By obtaining isothermal (adiabatic) electrical polarization data at measurement (starting) temperatures separated by <0.4 K, we identify a maximum temperature change of ~2 K due to a maximum field change of 26 kV cm-1, for starting temperatures in the range 300 - 315 K. These quasi in…
Electrically driven thermal changes in PbSc0.5Ta0.5O3 bulk ceramics are investigated using temperature and electric-field dependent differential scanning calorimetry and infrared thermometry. On first application and removal of electric field, we find asymmetries in the magnitude of isothermal entropy change $Δ$ S and adiabatic temperature change $Δ$ T, due to hysteresis. On subsequent field cycling, we find further asymmetries in the magnitude of $Δ$ T due to non-linearity in the isofield legs of entropy-temperature plots.
The present letter explores the electrocaloric effect (ECE) in the lead free oxide Ba0.8Ca0.2Ti0.95Ge0.05O3 ceramics (BCTG). The electrocaloric responsivity (dT/dE) was determined by two different methods using the Maxwell relationship (dT/dE)~(dP/dT)_E. In a first well-known indirect method, P-E hysteresis loops were measured in a wide temperature range from which the pyroelectric coefficient p_E=(dP/dT)_E and thus (dT/dE) were determined by derivation of P(T,E) data. In the second novel method the pyroelectric coefficient p_E and consequently the electrocaloric responsivity was determined by…
An applied electric field can reversibly change the temperature of an electrocaloric material under adiabatic conditions, and the effect is strongest near phase transitions. This phenomenon has been largely ignored because only small effects (0.003 K V^-1) have been seen in bulk samples such as Pb0.99Nb0.02(Zr0.75Sn0.20Ti0.05)0.98O3 and there is no consensus on macroscopic models. Here we demonstrate a giant electrocaloric effect (0.48 K V^-1) in 300 nm sol-gel PbZr0.95Ti0.05O3 films near the ferroelectric Curie temperature of 222oC. We also discuss a solid state device concept for electrical …
Tunable electrocaloric effect in lead scandium tantalate through calcium doping
研究通过钙掺杂调控铅钪钽的相变，实现电热效应的精确调节，发现不同掺杂浓度下相变温度变化，并展示其在低温范围内的应用潜力。
NdFeO3 modified polycrystalline ceramics with composition (NdFeO3)0.1-(Ba0.7Sr0.3TiO3)0.9 (NFBST) ceramics have been synthesized via solid-state reaction route. The Rietveld refinement of the XRD data confirmed the existence of a tetragonal phase (P4mm) and a hexagonal phase (P63/mmc) in the prepared sample. The coexistence of phases has been also further confirmed from the Raman spectroscopy. The SEM image revealed dense microstructure with well packed grains of different sizes. At room temperature lossy P-E loop and weak ferromagnetism is observed in NFBST system. Complex impedance spectrosc…
Electrical conductivity (sigma_dc) of the cellular Si/SiC ceramic composites has been measured over a temperature range 25-1073 K while the thermoelectric power (S) has been measured over 25-300 K. Remarkably, these cellular compounds developed through biomimetic route - where the ceramic system grows within a plant bio-template retaining the structural intricacies of the native templates - are found to exhibit excellent mechanical, thermal, and electrical properties quite comparable to or even better than those of the systems prepared through conventional ceramic route. The electrical conduct…
We report the polarization, displacement current and leakage current behavior of a trivalent nonpolar cation Al cation substituted lead free ferroelectric NBT-BT electroceramics with tetragonal phase and P4mm space group symmetry. Nearly three orders of magnitude decrease in leakage current were observed under electrical poling, which significantly improves microstructure, polarization, and displacement current. Effective poling neutralizes the domain pinning, traps charges at grain boundaries and fills oxygen vacancies with free charge carriers in matrix, thus saturated macroscopic polarizati…
Ferroelectric glass-ceramics are promising composite materials with dual properties, of high dielectric permittivity and high dielectric breakdown strength. In this context, new phosphate glass-ceramics 2BaO-0.5Na2O 2.5[(1-x)Nb2O5 xWO3]-1P2O5 (x=0, 0.1, 0.2, 0.3 and 0.4) designated as B0, B1, B2, B3, B4 respectively, were prepared by the controlled crystallization technology and then crystallized at high temperature of 760 °C for 10 hours. Subsequently, the obtained glass-ceramics were studied by Differential Scanning Calorimetry (DSC), X-ray powder diffraction (XRD), Raman, impedance spectros…
The thermal conductivity of polycrystalline bulk PZT (lead-zirconate-titanate) has been investigated according to electrical boundary conditions and poling. The thermal conductivity of poled PZT was measured in the poling direction for open circuit and short circuit conditions. The short circuit thermal conductivity had the largest thermal conductivity. The relationship between these two thermal properties, the electrothermal coupling factor $k_{33}^κ$, was found to be similar to the electromechanical coupling factor $k_{33}$ relating elastic compliance under short circuit and open circuit con…
A new lead-free (1-x)Li0.12Na0.88NbO3-xBaTiO3 (0 to x to 40) piezoelectric ceramics have been prepared using conventional ceramics processing route. Structural analysis revealed an existence of morphotropic phase boundary (MPB), separating orthorhombic and tetragonal phases, between the BaTiO3 content, x = 10-12.5. A partial phase diagram has been established based on temperature-dependent permittivity data for this new system and a nearly vertical temperature-independent MPB is observed. An improvement in electrical properties near MPB (e.g., for x = 12.5; εr = 10489 at Tm, d33 = 30 pC/N, kp …
The study of grain size effects in ferroelectric ceramics has attracted great research interest over the last 50 years. Although different theoretical models have been proposed to account for the variation in structure and properties with grain size, the underlying mechanisms are still under debate, creating a significant level of uncertainty in the field. Here, we report the results of a study on the influence of grain size on the structural and physical properties of Ba(Ti0.96Sn0.04)O3, which represents a model perovskite system, where the effects of point defects, stoichiometry imbalance an…
Thermal and Electrical Properties of (Cr,Mo,Ta,V,W)C High-Entropy Carbide Ceramics
研究了(Cr,Mo,Ta,V,W)C高熵碳化物陶瓷的合成、表征及其性能，发现密度增加导致晶粒生长和晶格参数增大，热导率随温度升高而增加，电导率随碳过剩量减少而降低，硬度稳定在约29GPa。
Structural, dielectric, ferroelectric and electrical properties of lead-free Ba0.9Sr0.1Ti0.9Sn0.1O3 ceramic prepared by sol-gel method
本研究采用溶胶-凝胶法制备无铅BSTSn陶瓷，表征其结构、介电、铁电与电学性能，证实其四方相结构、铁电特性及晶粒与晶界双弛豫导电机理。
Cation ordering is most common process detected in A$_{3}$B'B"$_{2}$O$_{9}$-based complex perovskites. Some important physical features of this system are due to the B-site ordering at long and short range. For microwave applications as filters and resonators, the 1:2 order is more appropriate. Otherwise, the oxygen vacancies and 1:1 order are considered the main factors behind the good performance of nonstoichiometric A$_{3}$B'$_{1+x}$B"$_{2-x}$O$_{9-δ}$-based ceramics as proton conductors. Until now, however, there are no available reports regarding the isolated effects of B-site order at lo…
Temperature-dependent dielectric permittivity of lead-free (LixNa1-x)NbO3 for nominal x = 0.04-0.20, prepared by solid state reaction followed by sintering, was studied to resolve often debated issue pertaining to exactness of morphotropic phase boundary (MPB) location along with structural aspects and phase stability in the system near MPB. Interestingly, a diffuse phase transition has been observed in the dielectric permittivity peak arising from the disorder induced in A-site and structural frustration in the perovskite cell due to Li substitution. A partial phase diagram has been proposed …
Dielectric behavior and conductivity mechanism in lead-free (100-x)(Li0.12Na0.88)NbO3-xBaTiO3 (0 to x to 40) piezoelectric ceramics were investigated using impedance spectroscopy over a wide temperature (-100 oC to500 oC) and frequency range (0.1 Hz to1 MHz). The grain and grain boundary response as well as the relaxation processes at different frequencies and temperatures were also discussed. A low frequency dispersion in dielectric permittivity (LFDD), a typical characteristic of high-temperature behavior was observed both below and above the ferro-paraelectric phase transition temperature, …
Lithium doping's effects on the microstructural,dielectric,energy storage,optical and electrical properties of BaTi0.89Sn0.11O3 ceramics
本研究合成不同锂掺杂量的锡钛酸钡陶瓷，表征其结构形貌等特征，发现x=6%的样品储能性能最优，且掺杂可降低带隙、提升电阻率。
Grain-Size Dependence of Thermal and Electrical Properties in (Cr,Mo,Ta,V,W)C1-δ High-Entropy Carbide Ceramics
本研究制备不同晶粒尺寸的(Cr,Mo,Ta,V,W)C₁₋δ高熵碳化物陶瓷，发现其室温热导率与电阻率无晶粒尺寸依赖性，推测本征无序与缺陷化学对性能影响更强。
The work presents the investigations of Li1.3Al0.3Ti1.7(PO4)3-xLiF Li-ion conducting ceramics with 0 < x < 0.3 by means of X-ray diffractometry (XRD), 7Li, 19F, 27Al and 31P Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) spectroscopy, thermogravimetry (TG), scanning electron microscopy (SEM), impedance spectroscopy (IS) and density method. It has been shown that the total ionic conductivity of both as-prepared and ceramic Li1.3Al0.3Ti1.7(PO4)3 is low due to a grain boundary phase exhibiting high electrical resistance. This phase consists mainly of berlinite crystalline phase as well…
The perovskite (1-x)YMnO$_3$-xBiFeO$_3$ binary system is very promising because of its multiferroic end members. Nanocrystalline phases have been recently obtained by mechanosynthesis across the system, and the perovskite structural evolution has been described. Two continuous solid solutions with orthorhombic Pnma and rhombohedral R3c symmetries were found, which coexist within a broad compositional interval of 0.5 < x < 0.9. This might be a polar-nonpolar morphotropic phase boundary region, at which strong phase-change magnetoelectric responses can be expected. A major issue is phase decompo…
Influence of Ga-Ge Doping on the Structural and Electrical Properties of Li7La3Zr2O12 Solid Electrolytes For Li ion Battery
本文通过固相反应制备Ga-Ge共掺杂Li7La3Zr2O12，发现0.20 Ga样品室温离子电导率达5.09×10^-4 S/cm，适用于全固态锂离子电池。
Lead-free Ba0.85Ca0.15Zr0.10Ti0.90O3 (BCZT) ceramics have demonstrated excellent dielectric, ferroelectric and piezoelectric properties in comparison to lead-based materials. The synthesis of pure and crystalline BCZT nanopowders at low temperatures of 25, 80 and 160 C was reported previously by using a sol-gel method followed by a hydrothermal route. In this study, the structural, dielectric and ferroelectric properties of sintered BCZT ceramics at 1250 °C for 10h were investigated. XRD measurements revealed the presence of a single perovskite phase at room temperature with the coexistence of…
The thermoelectric properties of Sr0.61Ba0.39Nb2O6 ceramics, reduced in different conditions, were investigated in the temperature region from 323 K to 1073 K. The electrical transport behaviors of the samples are dominated by the thermal-activated polaron hopping, the Fermi glass behavior, and the Anderson localized behavior from low temperatures to high temperatures, respectively. The lattice thermal conductivity presents a plateau at high temperatures, indicating a glass-like thermal conduction behavior. Both the thermoelectric power factor and the thermal conductivity increase with the inc…
Lead-free ceramics (K0.44+xNa0.52Li0.04)(Nb0.86Ta0.10Sb0.04)O3+x/2 (x=-0,06) were prepared by conventional solid state sintering. The results indicate a correlation between crystalline symmetry and electrical properties. Higher tetragonality was observed in samples with higher piezoelectric response. As the tetragonality increase the presence of polymorphic phase decrease associated with a reduction of the relaxor behaviour response. The ceramics with c/a = 1.011 ratio exhibit enhanced electrical properties. The Raman spectroscopy showed a certain asymmetry in the paraelectric phase above the …
Entropy engineering of BF-BT-based high-entropy ceramics for ultra-high energy storage performance
通过引入高熵钙钛矿氧化物到BF-BT基体中，利用多组分B位取代诱导晶格畸变、弛豫行为和晶粒细化，显著提高击穿强度，实现840 kV/cm的击穿强度和10.55 J/cm³的可恢复能量密度。
We use time-domain electrostatic force spectroscopy (TD-EFS) for characterising the dynamics of mobile ions in a partially crystallised LiAlSiO$_4$ glass ceramic, and we compare the results of the TD-EFS measurements to macroscopic electrical conductivity measurements. While the macroscopic conductivity spectra are determined by a single dynamic process with an activation energy of 0.72 eV, the TD-EFS measurements provide information about two distinct relaxation processes with different activation energies. Our results indicate that the faster process is due to ionic movements in the glassy p…
Piezoelectric and ferroelectric ceramics with a high Curie temperature (Tc) have attracted a growing attention owning to their applications under severe environments. In this work, phase structure, dielectric, ferroelectric and piezoelectric properties of (0.975-x)BiScO3-xPbTiO3-0.025Pb(Cd1/3Nb2/3)O3 ceramics (x = 0.58-0.64) were studied. A composition-induced structural transformation occurs from rhombohedral phase to tetragonal phase through an intermediate monoclinic phase with the increasing PT concentration. The relationship between structure and electrical properties of the system were d…
The efficiency of glass ceramic sealants plays a crucial role in high temperature applications performance and durability, such as oxygen separation from air. In order to develop suitable sealants, operating at about 950C, several glass-ceramics with different compositional additives and ratios in BAS system have been prepared and investigated. The effects of additive oxides, CaO, CoO, B2O3, as network modifiers on the thermal and dielectric properties of BAS glass-ceramic for further oxygen transport membrane OTM applications were evaluated and discussed. The addition of additives has evident…
Ba{[Gax,Tax]Ti(1-2x)}O3 ceramics with x equal to 0, 0.0025, 0.005, 0.01, 0.025 and 0.05 have been prepared by conventional solid-state reaction. Structural and dielectric characterization have been performed to investigate the effect of dipole-pair substitution concentration on the macroscopic dielectric properties. Ba{[Gax,Tax]Ti(1-2x)}O3 evolves from a classic ferroelectric to a diffuse phase transition (DPT) as x increases. Ba{[Gax,Tax]Ti(1-2x)}O3 for x > or = 0.01 possesses diffuseness parameters comparable to Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) and recently reported (Ba0.97Pr0.03)(Ti0.9425Ce…
Polycrystalline LiMnBO3 is a promising cathode material for Li-ion batteries. In this work, we investigated the thermal, structural and electrical properties of glassy and nanocrystallized materials having the same chemical composition. The original glass was obtained via a standard meltquenching method. SEM and 7Li solid-state NMR indicate that it contains a mixture of two distinct glassy phases. The results suggest that the electrical conductivity of the glass is dominated by the ionic one. The dc conductivity of initial glass was estimated to be in the order of 10-18 S.cm-1 at room temperat…
PbTiO3 has the highest tetragonal distortion (c/a=1.064) and highest spontaneous polarization among perovskite titanates. But, it is hazardous and hence one needs to reduce Pb content by substituting or reducing Pb content for use in applications. Pb(1-x)(K0.5Sm0.5)xTiO3 (0&x&0.5) perovskite powders were synthesized by sol-gel process, where Pb2+ was replaced by a combination of K+10.5Sm+30.5 (equivalent charge and comparable ionic radius) providing an excellent substitution model to study changes in structural and electrical properties. Vibrational properties and dielectric properties are mod…
Oxygen octahedra tilting is a common structural phenomenon in perovskites and has been subject of intensive studies, particularly in rhombohedral Pb(Zr,Ti)O3 (PZT). Early reports suggest that the tilted octahedra may strongly affect the domain switching behavior, dielectric and piezoelectric properties of PZT ceramics. In a way similar to that proposed for tilts, however, charged defects, associated with oxygen vacancies, may also inhibit the motion of the domain walls, resulting macroscopically in pinched hysteresis loops and reduced piezoelectric response. Here, we revisit the early studies …
As demand rises for flexible electronics, traditionally prepared sintered ceramic sensors must be transformed into fully new sensor materials that can bend and flex in use and integration. Negative temperature coefficient of resistance (NTC) ceramic thermistors are preferred temperature sensors for their high accuracy and excellent stability, yet their high stiffness and high temperature fabrication process limits their use in flexible electronics. Here, a low stiffness thermistor based on NTC ceramic particles of micron size embedded in an epoxy polymer matrix is reported. The effect of parti…
Ceramic Materials: From Atomic Bonding and Processing to Microstructure, Functional Properties, and Biomedical Applications
本综述围绕陶瓷材料的制备—微观结构—性能—表现关系，考察其特性、生物医用类型、新兴主题，指出脆性断裂等挑战，提出需整合多技术推动未来进展。
Towards understanding the defect properties in the multivalent A-site Na$_{0.5}$Bi$_{0.5}$TiO$_3$-based perovskite ceramics
研究多价A位Na₀.₅Bi₀.₅TiO₃基钙钛矿陶瓷的缺陷特性，揭示其电导率行为及缺陷模型对优化性能的指导作用。
Entropy stabilization has garnered significant attention as a new approach to designing novel materials. Much of the work in this area has focused on bulk ceramic processing, leaving entropy-stabilized thin films relatively underexplored. Following an extensive multi-variable investigation of polycrystalline (Mg$_{0.2}$Co$_{0.2}$Ni$_{0.2}$Cu$_{0.2}$Zn$_{0.2}$)O thin films deposited via pulsed laser deposition (PLD), it is shown here that substrate temperature and deposition pressure have strong and repeatable effects on film texture and lattice parameter. Further analysis shows that films depo…
Structural, electrical and magnetic properties of Bi0.9-xLa0.1ErxFeO3 (BLEFOx) (x = 0.05, 0.07, 0.1) polycrystalline ceramics prepared by solid solution route were studied. A phase transition from rhombohedral phase to monoclinic phase was observed for x=0.05-0.1 in (BLEFOx). We have measured phase transition temperatures both alpha-beta transition and low-Temperature (low-T) transitions in doped BiFeO3. The transition peak near to 835C corresponds to alpha to beta-phase transition of BiFeO3 were measured using diffential thermal analysis (DTA). Dielectric measurements shows the low-T transiti…
Metal ion implantation into ceramics has been demonstrated to be an effective and controllable technique for tailoring the surface electrical conductivity of the ceramic piece, and this approach has been used in a number of applications. Importantly, it provides a method for grading the voltage drop across high voltage insulators, and thereby increasing the maximum operational voltage that can be applied across the insulator without surface flashover. However a concern for the use of the method is the long term stability of the implantation-induced conductivity, this especially so if the impla…
Various elastic coefficients of Au2O3 doped PbO-B2O3-SeO2:Er2O3 (PBSE) glass ceramics were evaluated as functions of Au2O3 content using ultrasonic velocity measurements. The elastic coefficients and micro-hardness showed a decreasing tendency with the concentration of Au2O3. Such decrease is attributed to the increasing concentration of gold metallic particles and [SeO3]2- groups that acted as modifiers and induced imperfections in these samples. Obtained results were observed to be consistent with the conclusions drawn from spectroscopic studies that include X-ray photoelectron spectroscopy …
Probing the Effects of Heat Treatment Atmosphere on the Structural and Electrical Properties of NBT via Eu Photoluminescence
系统研究了预煅烧步骤中氧分压对Na0.5Bi0.465Sr0.02Eu0.005TiO3氧化物离子导电陶瓷的晶体结构、微观结构和电性能的影响，发现氧分压强烈影响Bi挥发、晶粒生长和氧空位浓度，并通过Eu3+光致发光揭示了局部结构演化与氧空位浓度的关联。
Processing-Controlled Structural Uniformity and Oxide-Ion Conduction in Na0.52Bi0.47TiO3 Ceramics Probed by Eu3+ Photoluminescence
通过Eu3+光致发光等多种表征手段，研究了前驱体混合方式对Na0.52Bi0.47TiO3陶瓷结构均匀性和离子传输的影响，揭示了加工引起的体缺陷与晶界阻挡之间的权衡，并通过Ca掺杂优化了电导率。
Effect of an internal chemical pressure on structural, optical, magnetic and electrical properties in Bi0.9RE0.1FeO3 Ceramics (RE =Gd3+,Tb3+,Dy3+)has been studied extensively. Some of the highlights are as follows; 1. Coexistence of orthorhombic Bragg reflections along with the R3c phase.(Structural Phase separation revealed from XRD and Raman spectroscopy) 2. Selective softening of phonon mode corresponding to oxygen motion suggests a significant destabilization in the FeO6 octahedra. 3. Three Charge transfer transitions (Fe1 3d\rightarrow Fe2 3d, Op \rightarrow Fed,Op \rightarrow Bip) and a …
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