Preparation and characterization of (Co_0:3Zn_0:7)(Ti_1–xSn_x)Nb₂O₈ microwave dielectric ceramics

Zn_0.7Co_0.3(Ti_1-xSn_x)Nb₂O₈ (x = 0.1, 0.15, 0.2, 0.25, 0.3, 0.35) microwave ceramics were prepared by traditional solidstate reaction method. The influences of Sn substituted for Ti on the phase constitution, crystal structure and microwave dielectric properties of Zn_0.7Co_0.3(Ti_1-xSn_x)Nb₂O₈ ceramics were discussed. The XRD patterns revealed the main phase of ZnTiNb₂O₈ and little content of Zn_0.17Ti_0.5Nb_0.33O₂ secondary phase. With further substitution of Sn, the lattice constant, volume and apparent density of the ceramics increased, the ceramic structure reached a maximal compactness at x = 0.2 which was shown on SEM. Tremendous improvement of Q × f and a declining trend of Ɛ_r and τ_f were obtained with increasing x value. Appropriate substitution value (x = 0.10) would ensure excellent microwave dielectric properties (Ɛ_r = 34.1, Q × f = 40562 GHz, τ_f =-5 ppm/°C) of the ceramics sintered at 1080 °C.