Low-loss microwave dielectrics in the Mg₂(Ti _0.95Sn_0.05)O₄-(Ca_0.8Sr _0.2)TiO₃ ceramic system

The microwave dielectric properties of the (1 - x)Mg₂(Ti _0.95Sn_0.05)O₄-x(Ca_0.8Sr _0.2)TiO₃ ceramic system prepared by mixed oxide route have been investigated. The crystal structures and the microstructures of the ceramics were characterized by means of X-ray and SEM. The microwave dielectric properties are strongly related to the density and matrix of the specimen. Combination of Mg₂(Ti_0.95Sn_0.05)O₄ (spinel-structured) and (Ca_0.8Sr_0.2)TiO₃ (perovskite-structured) forms a two-phase system and leads to a near-zero τ_f. With increasing x, the microwave Q × f decreased and ε_r increased. A new microwave dielectric material 0.91Mg ₂(Ti_0.95Sn_0.05)O₄-0.09(Ca _0.8Sr_0.2)TiO₃, possessing excellent microwave dielectric properties with a dielectric constant (ε_r) of 18.32, a Q × f of 109,200 GHz (where f = 9.5 GHz, is the resonant frequency) and a τ_f value ∼-0.5 ppm/°C at 1270 °C for 4 h, is proposed as a suitable candidate material for microwave applications requiring low dielectric loss.