(Pb_(0.97)La_(0.02))(Zr_(0.6)Sn_(0.4))O_(3)反铁电陶瓷的介电储能性能

Energy Storage Properties of(Pb_(0.97)La_(0.02))(Zr_(0.6)Sn_(0.4))O_(3)Antiferroelectric Ceramics

电介质电容器具有超高的功率密度和超快的充放电速率,因而在脉冲功率技术中具有应用前景。利用固相法制备了(Pb_(0.97)La_(0.02))(Zr_(0.6)Sn_(0.4))O_(3)(PLZS)反铁电陶瓷,研究了不同烧结温度下PLZS陶瓷的晶体结构、微观形貌、介电性能、反铁电及储能性能。结果表明,不同温度烧结的样品均具有正交钙钛矿结构,且随着烧结温度的升高,陶瓷的致密度逐渐提高、晶粒尺寸也逐渐增大。因此,最佳温度下(1225℃)烧结的陶瓷具有最佳的储能性能,可回收能量密度密度约13.3 J/cm^(3),储能效率约83.6%。

Introduction As one of the important electronic components in pulsed power devices,dielectric capacitors have wide applications in hybrid vehicles,and distributed power system.However,a relatively low energy density affects their application in portable and light–weight devices.The dielectric capacitors store and release energy in form of electrostatic polarization and depolarization of dielectric materials.Hence,achieving the maximum polarization(Pmax),small remanent polarization(Pr)and large electric breakdown strength(Eb)in dielectric materials is an effective approach to improve the energy storage properties.The antiferroelectric ceramics are one of the most prospect materials for energy storage due to their unique antiferroelectric–ferroelectric(AFE–FE)phase transition during charging and discharging process.As one of the classic antiferroelectric ceramics,Pb(Zr,Ti)O_(3) antiferroelectric ceramics are widely investigated.However,the content of Ti should be lower than 10%to stabilize the antiferroelectric phase,leading to the narrow windows for compositional regulation.In recent years,Pb(Zr,Sn)O_(3) antiferroelectric ceramics become popular because of the electric field induced multistage phase transition.In this paper,(Pb_(0.97)La_(0.02))(Zr_(0.6)Sn_(0.4))O_(3)(PLZS)antiferroelectric ceramic was synthesized via solid-state sintering at different temperatures.In addition,the crystal structures,microstructures,dielectric properties and energy storage properties of the ceramic were also investigated.Methods PbO,La_(2)O_(3),ZrO_(2) and SnO_(2) were used as raw materials,and weighted and mixed according to the stoichiometry.The mixed materials with alcohol were ground in a ball mill for 12 h.Afterwards,the suspension was dried,the powders were calcined at 900℃for 3 h,and then ground with alcohol for another 12 h.The dried powders with polyvinyl alcohol were pressed into disks with the diameter of 10 mm and the thickness of 1 mm.Finally,the green disks were sintered at 1200–1250℃for 2 h to obtain the densified ceramics.The crystal structures of ceramics were determined by X-ray diffraction(XRD).The surface microstructure of ceramics was characterized by scanning electron microscopy(SEM).For the measurement of dielectric properties,the ceramics were polished and covered with a silver paste,which was dried at 550℃for 10 min.The dielectric properties were analyzed by a dielectric test system at room temperature to 450℃,and the P–E loops of ceramics were determined by a ferroelectric analyzer.Results and discussion All the prepared ceramics show an orthorhombic perovskite structure without secondary phase.Moreover,some weak diffractions appear due to an antiparallel aligned adjacent Pb^(2+)in antiferroelectric ceramics.The microstructure of ceramics becomes denser with decreasing holes and increasing grain size as sintering temperature increases,which is beneficial to enhancing Eb.All the samples show three dielectric anomalies in a temperature-dependent dielectric constant(εr),indicating a successive phase transition between orthorhombic antiferroelectric phase(AFEO),tetragonal antiferroelectric phase(AFET),multicell cubic phase(MCC)and cubic paraelectric phase(PEC)as the temperature increases.In addition,the dielectric loss(tanδ)for all the samples is quite low(<0.2%)at a low temperature,which is also helpful to enhance Eb.All the samples sintered at different temperatures show double P–E loops and I–E curves,having the typical antiferroelectric properties.Furthermore,the polarization increases slowly at a relatively low electric field,and increases quickly at a moderate electric field due to the electric field induced AFE–FE phase transition.,the polarization increases more quickly with further increasing electric field because of the electric field induced FE–FE phase transition.Hence,the corresponding I–E curves exhibit electric field induced current peaks.As a result,the PLZS ceramic sintered at 1225℃has the optimal energy storage properties(i.e.,W_(rec) of 13.3 J/cm^(3)andηof 83.6%)at 480 kV/cm,indicating great potential applications in pulsed power devices.Note that a large Eb plays an important role in achieving superior energy storage properties,and a large Eb can be attributed to dense microstructure,small thickness and electrode area,moderateεr and low tanδ.Conclusions PLZS antiferroelectric ceramics were fabricated via solid–state reaction.The crystal structure,microstructure morphologies,antiferroelectric properties and energy storage behavior of PLZS ceramics sintered at different temperatures were investigated.All the samples exhibited an orthorhombic antiferroelectric phase.Also,the density of prepared ceramics improved,and grain size increased with increasing sintering temperature.Therefore,the sample sintered at 1225℃achieved the optimum energy storage properties(i.e.,recoverable energy density of 13.3 J/cm^(3)and efficiency of 83.6%).