Polarization Behavior And Energy Storage Applications In Bi-containing Double-site Disordered Relaxor Ferroelectrics

Energy storage dielectric materials have important applications in pulsed power devices due to their high power density and fast charging and discharging speed.Because of high maximum polarization,low remnant polarization and high breakdown field,relaxor ferroelectrics exhibits great potential of research and applications as one kind of energy storage dielectric materials.With the lone pair electron configuration,the Bi（6s）-O（2p）covalent bonds are stronger than Ti（4d）-O（2p）covalent bonds.The Bi-containing disordered relaxor ferroelectrics can maintain good energy storage properties and temperature stability with higher disorder while maintaining high maximum polarization due to the strong ferroelectric active Bi³⁺cations.In this work,the structure and energy storage behavior of three types of Bi-containing double-site disordered relaxor ferroelectrics are systematically investigated.（1）For the 0.5Ba[Ti_（1-x）Sn_x]O₃-0.5Bi(Mg_0.5Ti_0.5)O₃ double-site disordered relaxor ferroelectrics,all the compositions exhibit a pseudocubic perovskite structure.The composition with x=0.10 composition exhibits the best energy storage performance.The recoverable energy storage density,storage efficiency and power density are 1.91 J/cm³,81.04%（@150 k V/cm）and 30.04 MW/cm³（@120 k V/cm）,respectively.Meanwhile,the compositions also exhibits good temperature stability.The change of relative permittivity（>1850）is less than 11%in the temperature range of 100 and 400°C,and the dielectric loss is less than 0.02 in the temperature range of 150 and 400 ^oC.（2）For 0.95[（1-x）Sr Ti O₃-x Bi_1/2K_1/2Ti O₃]-0.05Bi(Zn_1/2Ti_1/2)O₃ double-site disordered relaxor ferroelectrics,all compositions show a single perovskite structure with the pseudocubic perovskite phase.The maximum value of the relative permitivitty at 1 k Hz increases with the decrease in the Sr Ti O₃ content,along with the enhanced polar order.The composition with x=0.55 exhibits the best energy storage characteristics.The recoverable energy storage density,storage efficiency and power density are 2.28 J/cm³,89.74%（@160 k V/cm）and 45.48 MW/cm³（@120 k V/cm）,respectively.The power density remains unchanged from 20 to 120°C,suggesting good temperature stability.（3）For(Bi_0.5K_0.5)_0.5Sr_0.5Ti_（1-x）Sn_xO₃ double-site disordered relaxor ferroelectrics,the main phase of all compositions is a perovskite structure.The symmetry is also pseudocubic.Compositions with x<0.1 shows a single perovskite structure.The impure phases,such as Sn O₂and Bi₂Ti O₇,could be detected in the compositions with x≥0.1,which are caused by the volatilization of Bi oxides and K oxides during the sintering process.The composition with x=0.05 exhibits the best energy storage characteristics.The recoverable energy storage,storage efficiency density and power density are 1.52 J/cm³,86.43%（@150 k V/cm）and 29.68 MW/cm³（@120 k V/cm）,respectively.