Research On The Microstructure And Energy Storage Performance Of PbZrO₃-based Dielectric Films

Antiferroelectric energy storage dielectric materials have the unique property of electric field induced phase structure transformation（electric field-induced phase transition character）,when the electric field is applied the field induced phase change polarization intensity increases rapidly and stores electrical energy and when the electric field is removed the depolarization process releases electrical energy.However,the electric field-induced phase transition process is accompanied by severe polarization/depolarization hysteresis effect and electric field-induced strain,and the antiferroelectric materials have the disadvantages of large energy loss and low breakdown strength,leading to low energy storage density and energy storage efficiency.Based on this,with antiferroelectric lead zirconate（PZO）as the research object,this thesis prepared PZO-based composite films by sol-gel method to regulate the microstructure,field-induced polarization behavior and electrical performance of PZO film by ionics doping,low temperature annealing,and construction of heterostructure,so as to improve the energy storage performance of PZO-based composite films.In addition,in order to meet the urgent demand of thin film capacitors in the field of flexible electronic devices,this thesis preliminarily explores the possibility of PZO films as flexible energy storage materials.The microstructure,polarization behavior and energy storage properties of Pb Zr_xTi_（1-x）O₃(PZ_xT_（1-x）)films with different Zr⁴⁺/Ti⁴⁺content ratios were investigated by Ti⁴⁺partially replacing Zr⁴⁺in PZO cells.The results show that the maximum and the remanent polarization of PZ_xT_（1-x）films increase with increasing Ti⁴⁺content.Although the energy storage density of PZ_0.52T_0.48film reaches 11.62 J/cm³,the efficiency is only 60.06%,which is a limited improvement compared with PZO film.The effect of the occupancy of Li⁺-Al³⁺ion pairs in PZO cells and their content on the polarization behavior of PZO film were investigated by Li⁺-Al³⁺ion pairs partially replace Pb²⁺in PZO cells.The results show that the Pb_0.94(Li_0.5Al_0.5)_0.06Zr O₃(P_0.94(L_0.5A_0.5)_0.06ZO)films exhibit relaxor ferroelectric-like polarization characteristics when the Li⁺-Al³⁺ion pair content is 6 mol.%,and the energy storage density increases to 49.09 J/cm³,but the energy storage efficiency is only 47.94%.In addition,in order to reduce the polarization loss caused by the long-range correlation of ferroelectric domains,low-temperature annealing is proposed to regulate the crystallization of P_0.94(L_0.5A_0.5)_0.06ZO films.The partially crystalline films annealed at550℃exhibit linear-like polarization characteristics,with significantly decreased polarization loss and increased breakdown strength,energy storage density of 58.71J/cm³,energy storage efficiency of 79.16%,and excellent frequency stability,temperature stability and electrical fatigue resistance.With flexible fluorphlogopite mica as the substrate,P_0.94(L_0.5A_0.5)_0.06ZO sol was spin-coated and grown on the mica substrate to realize the flexibility of inorganic energy storage films.Combined with annealing temperature optimization to further modulate the microstructure and polarization behavior of the flexible film to obtain excellent energy storage performance.The results show that partially crystalline P_0.94(L_0.5A_0.5)_0.06ZO film with 600℃annealing has low polarization loss and high breakdown strength,the energy storage density is 26.81 J/cm³,and the energy storage efficiency is 87.91%.It was found that the flexible crystalline films annealed at high temperature have higher polarization intensity when the same electric field is applied,but it is difficult to obtain high energy storage performance due to the limitation of breakdown strength.Based on this,P_0.94(L_0.5A_0.5)_0.06ZO/AO flexible multilayer composite films with different heterostructure were constructed by introducing Al₂O₃（AO）insulating layer to improve the breakdown strength of the crystalline P_0.94(L_0.5A_0.5)_0.06ZO films.When the applied electric field is 2500 k V/cm,the flexible AO/P_0.94(L_0.5A_0.5)_0.06ZO/AO/P_0.94(L_0.5A_0.5)_0.06ZO/AO（APAPA）multilayer composite film annealed at 700℃achieves an energy storage density of 41.78 J/cm³and an energy storage efficiency of 91.22%,and exhibited excellent energy storage performance frequency stability and bending fatigue resistance.