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 relative density of 98%, and exhibits optimal properties with a high dielectric permittivity ~16310, a large electrocaloric effect coefficient ~ 0.244Kmm/kV and an energy density storage of ~ 10.61 mJ/cm3.
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…
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…
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…
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 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…
We present a field theory approach to study changes in local temperature due to an applied electric field (the electrocaloric effect) in electrolyte solutions. Steric effects and a field-dependent dielectric function are found to be of paramount importance for accurate estimations of the electrocaloric effect. Interestingly, electrolyte solutions are found to exhibit negative electrocaloric effects. Overall, our results point toward using fluids near room temperature with low heat capacity and high salt concentration for enhanced electrocalorics.
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 …
We have recently observed a giant electrocaloric effect (12 K in 25 V) in 350 nm sol-gel Pb Zr_0.95 Ti_0.05 O_3 films near the ferroelectric Curie temperature of 242oC. Here we demonstrate a giant electrocaloric effect (5 K in 25 V) in 260 nm sol-gel films of the relaxor ferroelectric 0.9 PbMg_(1/3)Nb_(2/3)O_3 - 0.1 PbTiO_3 near the Curie temperature of 60oC. This reduction in operating temperature widens the potential for applications in novel cooling systems.
Refrigeration systems based on compression of greenhouse gases are environmentally threatening and cannot be scaled down to on-chip dimensions. In the vicinity of a phase transition caloric materials present large thermal responses to external fields, which makes them promising for developing alternative solid-state cooling devices. Electrocaloric effects are particularly well-suited for portable refrigeration applications; however, most electrocaloric materials operate best at non-ambient temperatures or require the application of large electric fields. Here, we predict that modest electric f…
Giant electrocaloric (EC) effect is observed in BaTiO3 multilayer thick film structure. The temperature change is as high as 4.0 oC under an applied electric field of 352 kV/cm. Most importantly, the EC effect is found to depend on the varying rate of the applied field. Based on the giant net cooling (~0.37 J/g) resulting from the difference in the varying rates of rising and falling fields, the kinetic EC effect provides an effective solution for the design of refrigeration cycle in ferroelectric micro-refrigerator.
Anomalous electrocaloric effect (ECE) with decreasing temperature upon application of an electric field is known to occur in antiferroelectrics (AFEs), and previous understanding refers to the field-induced canting of electric dipoles if there is no phase transitions. Here, we use a first-principle-based method to study the ECE in Nd-substituted BiFeO3 (BNFO) perovskite solid solutions, which has the Pnma-type AFE ground state. We demonstrate another scenario to achieve and explain anomalous ECE, emphasizing that explicit consideration of octahedral tiltings is indispensable for a correct unde…
We analyse the effects of applying an electric field on the critical temperature, Ts, at which superionicity appears in archetypal fast ion conductor CaF2 by means of molecular dynamics simulations. We find that the onset of superionicity can be reduced by about 100K when relatively small electric fields of ~50KV/cm are employed. Under large enough electric fields, however, ionic conductivity is depleted. The normal to superionic phase transition is characterised by a large increase of entropy, thereby sizeable electrocaloric effects can be realised in fast ion conductors that are promising fo…
Ferroelectric perovskite oxides possess a large electrocaloric (EC) effect, but usually at high temperatures near the ferroelectric/paraelectric phase transition temperature, which limits their potential application as next-generation solid-state cooling devices. We use classical molecular dynamics to study the electric field induced phase transitions and EC effect in PMN-PT (PbMg1/3Nb2/3O3-PbTiO3). We find that the maximum EC strength of PMN-PT occurs within the morphotropic phase boundary (MPB) region at 300 K. The large adiabatic temperature change is caused by easy rotation of polarization…
We report a heat dynamics analysis of the electrocaloric effect (ECE) in commercial multilayer capacitors based on BaTiO3 dielectric, a promising candidate for applications as a solid state cooling device. Direct measurements of the time evolution of the sample's temperature changes under different applied voltages allow us to decouple the contributions from Joule heating and from the ECE. Heat balance equations were used to model the thermal coupling between different parts of the system. Fingerprints of Joule heating and the ECE could be resolved at different time scales. We argue that Joule…
Ferroelectrics are attractive candidate materials for environmentally friendly solid state refrigeration free of greenhouse gases. Their thermal response upon variations of external electric fields is largest in the vicinity of their phase transitions, which may occur near room temperature. The magnitude of the effect, however, is too small for useful cooling applications even when they are driven close to dielectric breakdown. Insight from microscopic theory is therefore needed to characterize materials and provide guiding principles to search for new ones with enhanced electrocaloric perform…
A material with reversible temperature change capability under an external electric field, known as the electrocaloric effect (ECE), has long been considered as a promising solid-state cooling solution. However, electrocaloric (EC) performance of EC materials generally is not sufficiently high for real cooling applications. As a result, exploring EC materials with high performance is of great interest and importance. Here, we report on the ECE of ferroelectric materials with van der Waals layered structure (CuInP2S6 or CIPS in this work in particular). Over 60% polarization charge change is ob…
Due to critical environmental and technological issues, there is a pressing need to switch from current refrigeration methods based on compression of gases to novel solid-state cooling technologies. Solid-state cooling is based on the thermal response of materials to external magnetic, electric, or mechanic fields, the so-called caloric effect. The electrocaloric (EC) effect, which is caused by electric fields and typically occurs in polar materials, is particularly promising from a technological point of view owing to its good scalability and natural implementation in circuitry. Simulation of…
There is a surge of interest in developing environmentally friendly cooling technology based on the solid--state electrocaloric effect (ECE). Here, we point out that negative ECE with a fast cooling rate ($\approx$10$^{11}$ K/s) can be achieved by driving solid crystals to a high--temperature phase with a properly designed electric field pulse. Specifically, we predict that an ultrafast electric field pulse can cause a negative ECE up to 35 K in PbTiO$_3$ occurring on few picosecond time scales. We acquire and analyze these results by clarifying the mechanism of ECE during an adiabatic irrever…
Robust Electrocaloric Performance Enabled by Highly-Polar Frustrated Nanodomains in NaNbO3-Based Ferrodistortive Relaxor
Institutes of Physical Science and Information Technology, Leibniz International Joint Research Center of Materials Sciences of Anhui Province, Anhui University（安徽大学物理科学与信息技术学院，安徽省材料科学莱布尼茨国际联合研究中心）；School of Materials Science and Engineering, Hainan University（海南大学材料科学与工程学院）；Department of Physics, University of Science and Technology Beijing（北京科技大学物理系）；Hunan Provincial Key Laboratory of Thin Film Materials and Devices, School of Materials Science and Engineering, Xiangtan University（湘潭大学材料科学与工程学院薄膜材料与器件湖南省重点实验室）；Laboratory of Dielectric Functional Materials, School of Materials Science and Engineering, Anhui University（安徽大学材料科学与工程学院介电功能材料实验室）；Institute for Superconducting and Electronic Materials, Australian Institute for Innovative Materials, University of Wollongong（伍伦贡大学澳大利亚创新材料研究所超导与电子材料研究院）
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…
This study aims to shed light on processing pathways towards functional silicate ceramics, which show some promise in various emerging applications, including dielectrics and bioactive implant materials. Polycrystalline silicate ceramics of Neso, Soro and Inosilicate families were synthesised by three different techniques: (i) a co-precipitation method, (ii) a modified sol-gel method and (iii) standard solid-state reactions. Co-precipitated samples show increased sintering and densification behaviour compared to sol-gel and solid-state methods, with diametral shrinkage values during sintering …
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…
New approach for obtaining ceramic NASICON (Na$_3$Zr$_2$ (SiO$_4$)$_2$PO$_4$) films sintered in situ by a sol-gel method, using spray deposition and Near-Infra Red Sintering
This work investigates the compatibility of $Zr_{2}AlC$ MAX phase-based ceramics with liquid LBE, and proposes a mechanism to explain the observed local $Zr_{2}AlC$/LBE interaction. The ceramics were exposed to oxygen-poor ($C_{O}\le2.2 \cdot10^{-10}$ mass%), static liquid LBE at 500°C for 1000 h. A new $Zr_{2}(Al,Bi,Pb)C$ MAX phase solid solution formed in-situ in the LBE-affected $Zr_{2}AlC$ grains. Out-of-plane ordering was favorable in the new solid solution, whereby $\textit{A}$-layers with high and low-Bi/Pb contents alternated in the crystal structure, in agreement with first-principles…
The finite element method (FEM) is used to study the influence of porosity and pore shape on the elastic properties of model porous ceramics. The Young's modulus of each model was found to be practically independent of the solid Poisson's ratio. At a sufficiently high porosity, the Poisson's ratio of the porous models converged to a fixed value independent of the solid Poisson's ratio. The Young's modulus of the models is in good agreement with experimental data. We provide simple formulae which can be used to predict the elastic properties of ceramics, and allow the accurate interpretation of…
Polycrystalline bulk samples of PrFe1-xMnxO3 (x=0.0, 0.1, 0.3, 0.5) were synthesized by solid state reaction method to understand their structural, optical and dielectric properties
Bi_{4}Ti_{3}O_{12}-PVC composites were fabricated. Ceramics powders of bismuth titanate were prepared by the sol-gel method using bismuth nitrate pentahydrate Bi(NO_{3})_{3} \cdot 5H_{2}O and tetrabutyl titanate Ti(CH_{3}(CH_{2})_{3}O)_{4} as precursors. The Bi_{4}Ti_{3}O_{12}-PVC composites were fabricated from ceramics powders and polymer powders by hot-pressing method.
The magneto-electrocaloric effect which can be defined as the coupling between magnetocaloric and electrocaloric effects attracts currently considerable attention due to the advantages provided by the caloric effect in designing solid-state refrigeration technologies. The magneto-electrocaloric effect of a multiferroic antiferromagnetic spin system with the Dzyaloshinskii Moriya (DM) interaction is investigated in this paper. The DM interaction is assimilated to a coupling between an external site-dependent electric field and a local electric polarization. The external magnetic is also conside…
Results presented in this article demonstrate importance of taking into account such a phenomenon as the solid solution decomposition at the boundaries separating coexisting phases in lead-zirconate-titanate-based solid solutions with compositions belonging to the morphotropic boundary region of the "temperature-composition" phase diagram. It is shown that in the local decomposition of solid solutions in the vicinity of the boundaries separating the tetragonal and rhombohedral phases in lead-zirconate-titanate-based solid solutions lead to the changes of the chemical composition of the solid s…
We study the magnetoelectric and electrocaloric response of strain-engineered, multiferroic SrMnO$_3$, using a phenomenological Landau theory with all parameters obtained from \emph{first-principles}-based calculations. This allows to make realistic and materials-specific predictions about the magnitude of the corresponding effects. We find that in the vicinity of a tetracritical point, where magnetic and ferroelectric phase boundaries intersect, an electric field has a huge effect on the antiferromagnetic order, corresponding to a magnetoelectric response several orders of magnitude larger th…
High-entropy materials often outperform their lower-entropy relatives in various aspects, such as thermal stability and fracture toughness. While there are extensive research activities in the field of high-entropy alloys, comparably little is performed for high-entropy ceramics, and especially for high-entropy diborides. Here we show, that not only the hardness of ZrB2 layers can be improved from 43.2 to 45.8 to 47.2 GPa through the formation of solid solution ternary diborides (Zr0.61Ti0.39B2) and high-entropy diborides (Zr0.23Ti0.20Hf0.19V0.14Ta0.24B2), respectively, but especially their th…
Disorder enhances desired properties, as well as creating new avenues for synthesizing materials. For instance, hardness and yield stress are improved by solid-solution strengthening, a result of distortions and atomic size mismatches. Thermo-chemical stability is increased by the preference of chemically disordered mixtures for high-symmetry super-lattices. Vibrational thermal conductivity is decreased by force-constant disorder without sacrificing mechanical strength and stiffness. Thus, high-entropy ceramics propel a wide range of applications: from wear resistant coatings and thermal and e…
Aiiso Yufeng Li Family Department of Chemical and Nano Engineering（加州大学圣地亚哥分校艾思友峰李家族化学与纳米工程系；材料科学与工程计划）；Program in Materials Science and Engineering, University of California San Diego
SrNaBi2Nb3O12 powder was prepared via the conventional solid-state reaction method. X-ray structural studies confirmed the phase to be a three-layered member of the Aurivillius family of oxides. SrNaBi2Nb3O12 (SNBN) ceramics exhibited the typical characteristics of relaxor ferroelectrics, associated with broad and dispersive dielectric maxima. The variation of temperature of dielectric maxima (Tm) with frequency obeyed the Vogel-Fulcher relationship. Relaxor behavior was believed to be arising from the cationic disorder at A-site. Pinched ferroelectric hysteresis loops were observed well above…
Dielectric response as a function of frequency for high-permittivity dielectric and ferroelectric materials is discussed emphasizing the dynamic behaviour in the microwave and infrared range. After introducing the usual modelling of the polar phonon response and anharmonic hopping in locally dynamically disordered solids, including discussion of displacive and order-disorder ferroelectric phase transitions, we summarised the experimental data for selected ferroelectric, incipient ferroelectric and antiferroelectric perovskite ceramics (STO, BTO, BST, PZO), discussing the dielectric grain size …
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…
The evolution of grain structures in materials is a complex and multiscale process that determines the material's final properties. Understanding the dynamics of grain growth is a key factor for controlling this process. We propose a phenomenological approach, based on a nonlinear, discrete mass transfer equation for the evolution of an arbitrary initial grain size distribution. Transition rates for mass transfer across grains are assumed to follow the Arrhenius law, but the activation energy depends on the degree of amorphization of each grain. We argue that the magnitude of the activation en…
The development of thermal stresses inside refractory ceramics experiencing severe thermal shock is studied. The present analysis departs from the linear theory of thermal stresses as it accounts for temperature dependent thermal and mechanical material properties. Radiation surface heat exchange between the refractory component and its surroundings is included. A Finite Element Procedure is presented and a MATLAB code is developed. The nonlinear heat equation is solved for the temperature field and this solution is subsequently used in order to determine the stress field evolution. The finite…
