Microstructure and dielectric properties of Ba0.6Sr0.4TiO3-MgAl2O4 composite ceramics

(1 - x)Ba0.6Sr0.4TiO3-xMgAl(2)O(4) (x = 25, 30, 35 and 40 wt%) composite ceramics were prepared by conventional solid-state reaction method. The microstructures, dielectric properties and tunability of the composites have been investigated. The XRD patterns analysis reveals two crystalline phases, a cubic perovskite structure Ba0.6Sr0.4TiO3 (BST) and a spinel structure MgAl2O4 (MA). SEM observations show that the BST grains slightly dwindle and agglomerate with increasing amounts of MA. A dielectric peak with very strong frequency dispersion is observed at higher MA content, and the Curie temperature shifts to a higher temperature with increasing MA content. The ceramic sample with 30 wt% MA has the optimized properties: the dielectric constant is 1503, the dielectric loss is 0.003 at 10 kHz and 25 degrees C, the tunability is 23.63% under a dc electric field of 1.0 kV/mm, which is suitable for ferroelectric phase shifter. Crown Copyright (C) 2011 Published by Elsevier Ltd and Techna Group S.r.l. All rights reserved.