Papers by Keyword: ZnNb₂O₆

Abstract: To lower the sintering temperature of ZnNb₂O₆ microwave dielectric ceramic, ZnNb₂O₆ doped with B₂O₃ were prepared by the traditional solid state reaction method. The effects of the amount of B₂O₃ (0.25-5.0wt.%) on the microstructure, density and electrical performances were investigated. The results show that a pure columbite ZnNb₂O₆ phase was obtained for all B₂O₃-doped ceramics. The microwave dielectric properties reached the maximum values of ε_r = 24.1, Q×f = 19502 GHz, τ_f = -52.19 ppm/°C for 1wt% B₂O₃-doped ZnNb₂O₆ ceramic sintered at 1050 °C for 4 h. All of evidences suggest that the enhancement of microwave dielectric properties is due to the enhanced ions-energy and ionic diffusion with the increase of sintering temperature. Furthermore, B₂O₃ doping can generate liquid phase and reduce the activation energy of diffusion to promote the materials sintering.

Abstract: ZnNb2O6 ceramics with a columbite crystal structure, is a promising candidate for application in microwave devices. In this study, ZnNb2O6 nano-powders were prepared using Nb2O5 and Zn(NO3)2 as raw materials by Pechini method. The microstructure and crystal structure of ZnNb2O6 powders were investigated systematically using X-ray powder diffraction and SEM techniques. The effect of amount of citric and ethylene on the formation of sol-gel and the particle size of ZnNb2O6 powders were also investigated using orthogonal design. Finally, the optimum process parameters for synthesis ZnNb2O6 nano-powders were obtained in this study.

Abstract: MnCO3 was added into ZnNb2O6 ceramics to obtain excellent microwave dielectric properties. The samples were prepared by conventional solid-state reaction method. The effects of the amount of MnCO3 on sintering temperatures, ceramic densities and contraction were systematically investigated. The crystalline structure of ceramic body was analyzed by XRD. The ceramic microstructure was observed by SEM. The dielectric properties of ZnNb2O6 ceramics were measured by a vector network analyzer at microwave frequency, which showed: er = 22.65, Q×f = 36700 GHz (loaded value) and tf = -40 ppm/°C.