Crystal structure and microwave dielectric properties of (1 − x)ZnTa2O6–xTiO2 ceramics

Abstract

The crystal structural variations of (1−x)ZnTa2O6–xTiO2 ceramics sintered at 1250°C for 2h 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-α-PbO2, α-PbO2, trirutile, and rutile. For x⩽0.2, single-phase solid solutions of the tri-α-PbO2 structure were formed, whereas for x=0.4, a mixture of two solid solution phases based on the α-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-α-PbO2 or α-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×f) of 36,700GHz, and a temperature coefficient of the resonant frequency (τf) of +74ppm/°C.