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)O-3 (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 E-a = 0.032 eV, T-vf = 253.2 K, and v(0) = 2.63 x 10(13) 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 delta are 82% and 0.0034 for the coarse-grained sample. (C) 2004 Elsevier Ltd. All rights reserved.