Microwave frequency dielectric properties of hexagonal perovskites in the Ba5Ta4O15-BaTiO3 system

Abstract

The dielectric properties of the hexagonal perovskites Ba8Ta4+0.8xTi3-xO24 (x=O, 0.4, and 0.8), Ba10Ta8-0.8x TixO30 (x=0.6, 0.9, and 1.2) and Ba5Sr2Ta4ZrO21 were studied at microwave frequencies. XRD analysis did not reveal the presence of impurity phases in the obtained samples and the lattice parameters of solid solutions were linearly dependent on composition. These systems show a relatively high permittivity (27 < epsilon < 44) with a low dielectric loss (10,000 < Q xf < 31,000 GHz). Solid solutions Ba8Ta8-0.8x TixO30 with disordered face-sharing octahedra show higher Q x f values compared to ordered Ba8Ta4+0.8x Ti3-x O-24 compounds. Filling of empty vacancy layers by multicharged cations in the Ba-5(Ta, Ti)(4+delta)O-15 system (0 < delta < 1) along with Ba5Sr2Ta4ZrO21 intergrowth leads to decrease a quality factor. The effect of increasing Ti content in the pseudobinary Ba5Ta4O15-BaTiO3 system on microwave dielectric properties is discussed. (c) 2004 Elsevier Ltd. All rights reserved.