Crystal structure and microwave dielectric properties of ZnTi(Nb1−xTax)2O8 ceramics

The crystal structure and microwave dielectric properties of ZnTi(Nb1−xTax)2O8 (0 ≤ x ≤ 1) ceramics sintered at 1200 °C for 2 h were investigated. For x < 0.5, solid solution phases with the α-PbO2 structure, typical of ZnTiNb2O8, were obtained, whereas for 0.5 ≤ x < 1, mixtures of two solid solutions each respectively based on the α-PbO2 structure and a trirutile structure, were obtained. The relative amount of the trirutile-structured phases increased as the Ta content increased in a given region, and the end member ZnTiTa2O8 formed a single phase with the trirutile structure. The microwave dielectric properties were closely related to the crystal structures. A material with a near zero temperature coefficient of resonant frequency could be obtained for x = 0.8, and its dielectric constant and quality factor (Q × f) were 40.5 and 41,000 GHz, respectively.

► We examine the relationship between crystal structure and microwave dielectric properties.
► Two solid solution phases with α-PbO2 and trirutile structures are identified.
► The temperature coefficient of resonance frequency is tunable to near zero.