Structural Evolution and Microwave Dielectric Properties of<i>x</i>Zn_0.5Ti_0.5NbO₄-(1–<i>x</i>)Zn_0.15Nb_0.3Ti_0.55O₂Ceramics

Abstract

Structure and microwave properties of xZn_0.5Ti_0.5NbO₄-(1 - x)Zn_0.15Nb_0.3Ti_0.55O₂ ceramics in the range of x = 0.0-1.0 were investigated. Rietveld refinement analysis and Raman spectra show that rutile- and orthorhombic-type solid solutions formed at 0-0.2 and 0.65-1, a composite at 0.2-0.64. In the solid solution regions, chemical bonds are enlarged. In this case, the Zn/Ti/Nb-O1 bond covalency and bond susceptibility are reduced, and lattice energy and thermal expansion coefficient increase along with x increases, which is mainly responsible for the development of microwave dielectric properties. Furthermore, far-infrared spectra and a classical oscillator model were used to discuss the intrinsic dielectric properties in detail. Temperature stable ceramic was obtained for x = 0.516: ε_r ∼ 46.11, Q × f ∼ 27 031 GHz, and τ_f ∼ -1.51 ppm/°C, which is promising for microwave applications.