Preparation And Research Of Energy Storage Properties Of BaTio₃-K_0.5Bi_0.5TiO₃ Based Ceramics

Dielectric capacitors is the most important energy storage components in the pulse power device area due to its high power density,quick speed of charge and discharge,good stability and long service life.At present,the dielectric capacitors have lower energy storage density and energy storage efficiency and can not meet the actual demands.Barium titanite is widely used in thermistors and multilayer ceramic capacitors due to its excellent dielectric and ferroelectric properties.The recent research shows that doping could improve the energy storage performance of BT-based ceramic.In this paper,KBT,KN,NN and MgO were doped into BT to improve its energy-storage density by increasing its maximum polarization,decreasing its remanent polarization and enhancing its dielectric breakdown strength.The crystal structures,micro-morphologies,dielectric properties,ferroelectric properties energy-storage properties and the relationship between properties of these materials were studied.?1-x?BT-xKBT ceramics were prepared by conventional solid state reaction method.The XRD patterns revealed that all samples show a single perovskite phase and no secondary phase was observed.The microstructure of all ceramic samples is dense,and the average grain size decreases with the increase of KBT content.With increasing KBT content,the Curie temperature of the BT-based ceramics gradually shift towards the high temperature.A relatively large maximum polarization of 21.2?C·cm^-2 and appropriate remanent polarization of9.3?C·cm^-2 was obtained in the x=0.08 samples.The addition of KBT improves the energy storage performance of BT-based ceramics?1-x??0.92BT-0.08KBT?-x KN ceramics were prepared by conventional solid state reaction method.The XRD patterns revealed change in crystal symmetries from tetragonal to pseudocubic structure with increasing KN contents.The introduction of KN induces two dielectric anomalous peaks,and the dielectric anomalies in the high-temperature region move to the lower temperature with the increase of KN contents.When x>0.04,the ferroelectric phase content of ceramics decreases,leading to the hysteresis loop become slim.The optimum energy storage properties at 12.5 kV·mm^-1 was obtained of x=0.08,with energy storage density is 0.89 J·cm^-3 and energy storage efficiency is 56%.?1-x??0.92BT-0.08KBT?-x NN ceramics were prepared by conventional solid state reaction method.Variation of defect dipole concentration leads to the average grain size of the ceramics reduced.With the increase of NN,the c/a and unit cell volume of ceramics decreased,and the crystal structure changes from tetragonal phase to pseudo-cubic phase.All samples show a weak frequency dispersion phenomenon.With the increase of NN,the Curie temperature moves to the low temperature region,and the permittivity first increases and then decreases.When x=0.02,the permittivity reaches the maximum value.When x?0.06,the P_r of the ceramic is greatly reduced and the hysteresis loop become slim.The introduction of NN significantly improves the evenness of grains,which helps to improve the uniformity of the domains and improve the flexibility of the domain steering.The optimum energy storage properties at 21.2 kV·mm^-1 was obtained for the composition of x=0.06,with energy storage density reaching 1.80 J·cm^-3 and energy storage efficiency is60.1%.Compared with KN,the introduction of NN could improve the energy storage properties of 0.92BT-0.08KBT ceramic more effectively.0.94?0.92BT-0.08KBT?-0.06NN-x wt%MgO ceramics were prepared by conventional solid state reaction method.When x?3,the secondary phase MgO and Mg_1.5Ti_1.25O₄ appeared.With the increase of MgO addition,the unit cell volume of samples increases and the c/a decreases.With the increase of MgO content,the content of non-ferroelectric phase increases,and the maximum polarization decreases.When x=4,the P_m of the ceramic sample decreases to25.7?C·cm^-2.The introduction of MgO effectively improves the breakdown strength of ceramics.When x=4,the breakdown field can reach 24.3 kV·mm^-1.The energy density of 0.94?0.92BT-0.08KBT?-0.06NN-3 wt%MgO ceramic is2.33 J·cm^-3,the?is 71%and the breakdown field strength is 23.6 kV·mm^-1.