Effects of Ta⁵⁺ Substitution on Structure Transition and Microwave Dielectric Properties of Zn(Nb_1-xTa_x)₂O₆ Ceramics

The crystal structure, phase relation, microstructure and dielectric properties of microwave dielectric ceramics comprised of Zn(Nb1-xTax)2O6 were investigated systematically using XRD, SEM and a network analyzer in this study. XRD results show that the Zn(Nb1-xTax)2O6 ceramics have the orthorhombic for all x values. However, two kinds of solid solutions phase regions based on columbite structure and ZnTa2O6 structure were observed. SEM results show that the growth of grains is restrained with increase of Ta content in Zn(Nb1-xTax)2O6 ceramics. The dielectric properties exhibited a significant dependence on the crystal structure and compositions of the ceramics. The dielectric constant (εr) of Zn(Nb1-xTax)2O6 ceramics increased with increasing Ta content. However, the quality factors (Q×f) of this system show a different trend, and decrease with increasing Ta content. At x=0.65, a zero temperature coefficient of resonant frequency ( τ f) can be realized in Zn(Nb1-xTax)2O6 ceramics system.