Effect of Zn_0·17Nb_0·33Ti_0·5O₂ on the microwave dielectric properties of ZnTiNb₂O₈ ceramics

An original (1-x)ZnTiNb₂O₈-xZn_0.17Nb_0·33Ti_0·5O₂ (x = 0.35–0.75) composite ceramics were prepared by the traditional solid-state method. X-Ray diffraction and Raman spectroscopy results illustrated that only ZnTiNb₂O₈ and Zn_0·17Nb_0·33Ti_0·5O₂ were synthesized without any extra phase. The morphology and microstructures of the microwave dielectric ceramics were characterized by scanning electron microscopy and energy disperse spectroscopy. The addition of Zn_0·17Nb_0·33Ti_0·5O₂ not only effectively adjusted the τ_f of ZnTiNb₂O₈ matrix from −39.55 ppm/°C to 54.32 ppm/°C, but also significantly increased ε_r from −39.55 ppm/°C to 54.32 ppm/°C. But the Q × f values deteriorated from 36,914 GHz to 21,077 GHz as x increased. The ceramic with near-zero τ_f was synthesized at x = 0.55, meanwhile, 0.45ZnTiNb₂O₈-0.55Zn_0·17Nb_0·33Ti_0·5O₂ ceramic sintered at 1200 °C possessed attractive microwave dielectric properties: ε_r = 39.08 (6.2 GHz), Q × f = 31,384 GHz, and τ_f = −6.45 ppm/°C.