Study on the microwave dielectric properties of 0.84MgNb_2-x(Ti_1/2W_1/2)_xO₆-0.16CaTiO₃ ceramic

In order to meet the demand of high-quality microwave dielectric ceramics for the development of wireless communication, 0.84MgNb_2-x(Ti_1/2W_1/2)_xO₆-0.16CaTiO₃(x = 0, 0.03, 0.05, 0.07, 0.09, 0.11) microwave dielectric ceramics were prepared by solid-phase method. The effects of phase structure, sintering properties, microstructure, and microwave dielectric properties of 0.84MgNb₂O₆-0.16CaTiO₃ ceramics in which the Nb⁵⁺ ionic substituted with different contents of (Ti_1/2W_1/2)⁵⁺ were studied. The results indicate that the partial Nb⁵⁺ in the 0.84MgNb_2-x(Ti_1/2W_1/2)_xO₆-0.16CaTiO₃ nominal composition are replaced by the complex cations (Ti_1/2W_1/2)⁵⁺ in the crystal structure, and no new phase is produced. With the gradual increase of (Ti_1/2W_1/2)⁵⁺ addition, the bulk density of 0.84MgNb_2-x(Ti_1/2W_1/2)_xO₆-0.16CaTiO₃ ceramics increased, the sintering temperature did not significantly change, the ceramic cell volume decreased, and the material polarizability and filling rate decreased, resulting in a decrease in the ceramics’ dielectric constant ε_r, the quality factor Q × f increases, and the frequency temperature coefficient τ_f shifts to a positive value. The 0.84MgNb_1.95(Ti_1/2W_1/2)_0.05O₆-0.16CaTiO₃ ceramic with x = 0.05 composition sintered at 1250 °C for 4 h holding time has the best microwave dielectric properties: ε_r = 21.52, Q × f = 96983 GHz, and τ_f = − 3.8 × 10^–6/ °C.