No abstract

Solid solutions of 0.35(Ba,Ca)(Zr,Ti)O3-0.65(K0.5Bi0.5)TiO3 (BCZT-KBT) having various Ca and Zr contents were synthesized by solid state reaction. The sintered ceramics exhibited interesting features comprising core-shell type microstructures and relaxor ferroelectric behaviour. The influence of air-quenching on structure and electrical properties has been systematically investigated. The results indicate that the compositional heterogeneity in the shell regions, for the slow-cooled state, was reduced by air quenching. Improvements are evident in ferroelectric tetragonal phase content, accompanied by increased polarisation values and depolarisation temperatures. Comparing the results obtained for two BCZT compositions, it was demonstrated that the stability of the ferroelectric tetragonal phase in slow-cooled BCZT-KBT samples was improved for the ceramic with lower Ca and Zr concentrations, denoted x=0.06, comparing with that for higher levels, denoted x=0.15. Furthermore, the electric field-induced ferroelectric state in the quenched ceramic with x=0.06 was found to be more stable during heating, yielding an enhanced depolarisation temperature.

The noticeable progression in the power electronic devices pushes a crucial demand to develop dielectrics with low loss, good temperature stability and high energy-storage density in addition to enhanced energy recovery characteristics. These properties are very important in order to use in advanced pulsed capacitors. Capacitors form a main part of many modern electrical and electronic devices. In this regards, relaxor ferroelectrics form an appropriate candidate for ceramic-based capacitor applications, due to their low loss and high energy density. This review provide theoretical basis at first, which help to evaluate the capacitors characteristics that contribute to high energy storage behavior. Moreover, serves to give an overall summary on latest development on electric energy-storage performance in the candidate materials, particularly in bismuth based peroviskite materials. For example, Bi0.5Na0.5TiO3, BiFeO3 and their solid solutions with BaTiO3 or with K0.5Na0.5NbO3.