Crystal structure and microwave dielectric properties of (1-x)ZnTa2O6-xTiO(2) ceramics

Abstract

The crystal structural variations of (1 - x) ZnTa2O6-xTiO(2) ceramics sintered at 1250 degrees C for 2 h were investigated, and the relationship of these variations with the microwave dielectric properties were studied. Four types of crystal structures were identified with increasing x: tri-alpha-PbO2, alpha-PbO2, trirutile, and rutile. For x <= 0.2, single-phase solid solutions of the tri-alpha-PbO2 structure were formed, whereas for x = 0.4, a mixture of two solid solution phases based on the alpha-PbO2 and trirutile structures was obtained. For x = 0.5, a single phase of ZnTiTa2O8 with the trirutile structure was obtained, and for x >= 0.6, the ceramics formed single-phase solid solutions of the rutile structure. The microwave dielectric properties of the ceramics were changed by the crystal structural transitions: for x < 0.4, the phases of the tri-alpha-PbO2 or alpha-PbO2 structures exhibited ZnTa2O6-like dielectric behavior, while for x >= 0.4, the phases of the trirutile or rutile structure exhibited more TiO2(rutile)-like behaviors as x increased. The ZnTiTa2O8 (x = 0.5) ceramics had a dielectric constant (k) of 46.2, a quality factor (Q x f) of 36,700 GHz, and a temperature coefficient of the resonant frequency (tau(f)) of + 74 ppm/degrees C. (C) 2012 Elsevier B.V. All rights reserved.