Preparation And Electrical Properties Of PLZT Antiferroelectric Ceramics

With the continuous progress of electronic components recent years,new materials have gradually drawn researchers’ attention.Antiferroelectric capacitors are widely used in medical treatment,electrical vehicles,high-energy laser and other fields.Lead lanthanum zirconate titanate(PLZT),which has been practically applied,has been widely studied.The literature shows that the ceramic preparation process has a direct impact on the electrical properties of the material,but the solid-phase reaction process of PLZT synthesis is not yet clear,and the specific effect of the synthesis process on the material properties is rarely reported.At the same time,relaxor antiferroelectricity with high lanthanum content has become a research hotspot recent years,which privides a solution is to balance energy storage density and efficiency.In this paper,from the perspective of promoting its engineering application,the solid-phase synthesis process is studied and the influence of the synthesis process on the electrical properties of PLZT ceramics is pointed out.Based on the influence of electrical properties,the optimal composition formula of good comprehensive energy storage performance was obtained.The influence of fringe field effect on the electrical properties of PLZT antiferroelectric ceramics was studied,and its influence mechanism was qualitatively determined.Firstly,The solid-phase reaction of PLZT starts at 700 °C when Pb3O4 begins to decompose,and then a solid-phase reaction occurs between 700-800 °C to synthesize PZT.The reaction temperature of La2O3 in PLZT is the highest,starting from about800 °C;In PLZT-based antiferroelectric ceramics,the higher the La content,the more impurity phases are generated during synthesis,which are mainly La2O3 and Zr O2 when the temperature is below 1000 °C,but La2Zr2O7 impurities appearing when the temperature is raised to above 1000 °C;synthesis temperatures have different effects on the electrical properties of PLZT antiferroelectric ceramics with different La contents,except the phase transition electric field decreases monotonically with the increasing synthesis temperature because of the weaken antiferroelectricity.Secondly,the increase of La content will reduce the ferroelectric long-range order of PLZT antiferroelectric ceramics after AFE-FE phase transition,making its relaxor behavior stronger and the phase transformation process of the ceramics is more diffused;the increase of La content also makes the ceramics changing from tetragonal phase into pseudo-cubic phase.This structural change is one of the reasons for the weakening of the antiferroelectricity of the ceramic.The weakening of the antiferroelectricity will also reduce the Curie temperature of the ceramic;the increase of Ti content will weaken the antiferroelectricity of PLZT and the phase transition electric field and the Curie temperature of the ceramics are also decrease.The XRD peak fitting of the ceramics shows that La0.08 is an antiferroelectric component,La0.10 is relaxor antiferroelectric and La0.12 and La0.14 are relaxor ferroelectric.Through the analysis of the temperature-varying dielectric constant curve and hysteresis loop of the ceramic,it is found that under the same electric field,relaxor antiferroelectric has the best comprehensive energy storage characteristics,among which La0.10Ti0.16 shows energy storage density of 1.30 J/cm3 and the charge-discharge efficiency of 88.0%,which is the best comprehensive performance.The phase transition process of the ceramic has obvious segmental change characteristics,and its specific phase transition process is RAFE-RFE-MCC state-PE.But the MCC state is obviously not conducive to energy storage,and this phase transition reduces the high temperature stability of the material.Third,the antiferroelectric ceramics are significantly affected by the fringe field effect.The experiment found that the maximum polarization intensity of the sample with a diameter of 1.2 mm electrode exceeds 64.6% compared with the sample with 10 mm electrode,and the change trend of the polarization intensity is inversely proportional to the electrode area.The fringing field effect is mainly affected by the change of the polarization volume.Due to the uneven distribution of the fringe electric field,polarization volume around the edge is obviously affected by the change of the electrode specification.At the same time,the change of the electrode thickness will also affect the polarization strength of the ceramic.The simulation results show that,The change of the electric field distribution is indeed affected by the uneven distribution of the electric field in the capacitor.The effective area at the edge of the capacitors with symmetric electrode diameters of 2mm,4mm and 8mm increase 25.8%,14.5% and 7.4%respectively.For the asymmetric electrodes of 8-2mm and 8-4mm,the increase area of the effective electric field at the edge of the capacitor is 6.5% and 3.5% respectively,and the increase area of the effective electric field at the edge of the capacitor with a thickness of 0.1mm and 0.3mm is 8.4% and 17.1%,respectively.The simulation results are similar with the experiment.