Effect of grain size on the electrical properties of (Ba,Ca)(Zr,Ti)O3 relaxor ferroelectric ceramics

( Ba 0.90 Ca 0.10 ) ( Zr 0.25 Ti 0.75 ) O 3 (BCZT) relaxor ferroelectric ceramics with grain sizes of 0.85, 2.5, 15, and 30μm were prepared from powders synthesized using a sol-gel process. The effects of grain size and dc field on the dielectric properties and tunabilities of BCZT ceramics were investigated. As the grain size decreased, the maximum dielectric constant decreased and the transition temperature increased. The BCZT ceramics with various grain sizes showed a typical relaxor ferroelectric behavior. The dielectric relaxation rate follows the Vogel–Fulcher relation. The dielectric constant is greatly suppressed and the low loss is obtained under a dc electric field. At room temperature (300K) and 20kV∕cm, the tunabilities and figures of merit are 42% and 62, 51% and 98, 56% and 193, and 51% and 182, respectively, for the BCZT ceramics with grain sizes of 0.85, 2.5, 15, and 30μm.