Effects of grain size on the dielectric properties and tunabilities of sol–gel derived Ba(Zr0.2Ti0.8)O3 ceramics

Barium zirconante titanate Ba(Zr0.2Ti0.8)O3 (BZT) ceramics were prepared using a sol–gel process. The effect of grain size and dc field on the dielectric properties of BZT ceramics were investigated. The coarse-grained sample undergoes a structural phase transition, but medium- and fine-grained samples showed diffuse phase transition characteristics. As the grain size decreased, the maximum dielectric constant and the transition temperature decreased. The fine-grained sample showed a ‘relaxor-like’ ferroelectric behavior, the dielectric relaxation rate follows the Vogel–Fulcher relation with Ea=0.032 eV, Tvf=253.2 K, and ν0=2.63×1013 Hz. The dielectric constant is greatly suppressed and low loss is obtained under dc electric field. At room temperature (300 K) and 20 kV/cm, the tunability (k) and loss tan δ are 82% and 0.0034 for the coarse-grained sample.