Effects of quenching on phase transformations and ferroelectric properties of 0.35BCZT-0.65KBT ceramics

Solid solutions of 0.35(Ba,Ca)(Zr,Ti)O-3-0.65(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.