Dielectric properties of new perovskite ceramics (Na1/4Bi3/4)(Mg1/4Ti3/4)O3 and (K1/4Bi3/4) (Mg1/4Ti3/4)O3

New perovskite ceramics (Na1/4Bi3/4)(Mg1/4Ti3/4)O-3 (NBMT) and (K1/4Bi3/4)(Mg1/4Ti3/4)O-3 (KBMT) were synthesized using solid-state reaction method. These two new ceramics have cubic symmetry structure at room temperature. Both NBMT and KBMT show a frequency-dependent broad dielectric maximum epsilon(m)' around 200-330 degrees C, and the dielectric constant epsilon' varies from several hundreds at 20 degrees C to about two thousands of epsilon(m)'. No ferroelectric behaviour is observed. Between 10(2) and 10(6) Hz, the epsilon' exhibits frequency dispersion in rather wide temperature range. The frequency dependence of epsilon' follows the formula, epsilon'(v) = epsilon'(1 Hz) - B log v, at low temperature side of the T-m. (c) 2006 Elsevier Ltd. All rights reserved.