Study On Grain Boundary Structure And Dielectric Properties Of ?Sr,Pb,Bi? Tio₃-based Storage Ceramics

Energy storage dielectric ceramics are very suitable as energy storage devices for pulse power devices due to the high discharge power density and excellent working stability.?Sr,Pb,Bi?TiO₃?SPBT?dielectric ceramics exhibited high discharge power density,high discharge efficiency,high dielectric constant and low dielectric loss.In this paper,SPBT-based dielectric ceramics with different grain boundary structures were prepared via the changing of dopants.And systemically investigation on the dielectric properties have been done for?Sr,Pb,Bi?TiO₃dielectric ceramics aimed at the core problem of grain boundary structure.The effects of dopants on the grain boundary structure of SPBT-based dielectric ceramics have been investigated.?1-x?Sr_0.7Pb_0.15Bi_0.1TiO₃-xBi₄Ti₃O₁₂??1-x?SPBT-xBIT?multiphase ceramics with SPBT and Pb₃Bi₄Ti₆O₂₁?PBT?were prepared by low temperature sintering with the doping of BIT.Compared with SPBT,PBT exhibited different structural properties,which caused the reduction of grain boundary density and the increase of ferroelectric domains.?1-x?Sr_0.7Pb_0.15Bi_0.1TiO₃-xBi_0.5Na_0.5TiO₃??1-x?SPBT-xBNT?solid-solutions were prepared by high temperature sintering with the doping of BNT.The elemental composition of the grains had been changed by the doping of BNT,and the insulation of the grain boundaries had been enhanced.The structure of the grain boundary have been changed due to the change of the elemental composition,and the micro domain disappeared,which caused the change of the domain structure.The effects of grain boundary structure on the breakdown strength have been investigated.It is found that the reduction of grain size is beneficial to increase the grain boundary density of materials.But it also leads to obvious interfacial polarization effects,which caused the reduction of breakdown strength.The grain boundary density and the concentration of space charge were reduced by BIT doping,which reduced the effect of the interfacial polarization effectively.It is found that the incorporation of BNT enhanced the insulation of SPBT grain boundaries,which improved the breakdown strength of materials effectively.However,the incorporation of BNT lead to the appearance of lead-bismuth compounds,which lead to an adverse affect for the dielectric properties of the materials.The effects of grain boundary structure on the dielectric-temperature characteristics have been investigated.Both BIT and BNT exhibited high Curie temperature.It is found that the Curie peak of the material can be moved and broaden with the doping BIT or BNT,and then the effect of reduction of capacitance variation of capacitor achieved.By the comparation of capacitance variation of ceramic with different sintering temperature,it is found that the internal stress of the grain boundaries was inceased effectively with the reduction of grain size,and the capacitance variation of ceramic was decreased.The effects of grain boundary structure on the energy storage properties have been investigated.The density of domain structure increased with the incorporation of BIT and the appearance of the PBT in the?1-x?SPBT-x BIT ceramics,and the ferroelectricity of ceaamic was increased.The grain boundary structure of?1-x?SPBT-x BNT ceramics have been changed with the doping of BNT,the micro domain disappeared,and the density of domains increased,which caused the increase of antiferroelectricity.As the increases of the density of domains,more energy would be consumed by the reorientation of domain wall,which caused the increase of dielectric loss and the discharge efficiency decreased.In addition,the energy storage density of?1-x?SPBT-xBNT ceramics have been increased effectively by BNT doping.