Effect of Bi-12(Ti1/2Si1/2)O-20 on the low temperature sintering of Bi-2(Zn1/3Nb2/3)(2)O-7 ceramics and their microwave dielectric properties

Abstract

The effects of Bi-12(Ti0.5Si0.5)O-20 (BTS) on the low temperature sintering of the Bi-2(Zn1/3Nb2/3)(2)O-7 (BZN) pyrochlore materials and their microwave dielectric properties were investigated. BTS was very effective to lower the sintering temperature by 100-150 degrees C, which was confirmed by characterizing density and microstructure. The BZN phase of pure monoclinic zirconolite pyrochlore was observed up to 3 wt% BTS addition within XRD detection limit. With the increase of BTS to 5 wt%, the Bi-based secondary phase (Bi3NbO7) appeared and the tetragonal-cubic phase transformation of Bi3NbO7 occurred with increasing sintering temperature from 850 to 950 degrees C. In the case of 0.5 wt% BTS added specimens, the microwave dielectric properties such as dielectric constant (epsilon(r)) of 74-78, quality factor x frequency (Qf) of 3500-4100 and a temperature coefficient of resonance frequency (TCF) between -71.9 and -75.1 ppm/degrees C were obtained at relatively lower sintering temperature ranging from 850 to 900 degrees C. When BTS is further added, epsilon(r) was nearly unchanged, the Qf value decreased while TCF slightly increased to positive direction. These results can be explained mainly in terms of the intrinsic properties of the secondary Bi3NbO7 phase influenced by its sintering temperature. (C) 2007 Elsevier Ltd. All rights reserved.