Low-loss microwave dielectrics in the Mg2(Ti0.95Sn0.05)O4–(Ca0.8Sr0.2)TiO3 ceramic system

The microwave dielectric properties of the (1 − x)Mg2(Ti0.95Sn0.05)O4–x(Ca0.8Sr0.2)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(Ti0.95Sn0.05)O4 (spinel-structured) and (Ca0.8Sr0.2)TiO3 (perovskite-structured) forms a two-phase system and leads to a near-zero τf. With increasing x, the microwave Q × f decreased and ɛr increased. A new microwave dielectric material 0.91Mg2(Ti0.95Sn0.05)O4–0.09(Ca0.8Sr0.2)TiO3, possessing excellent microwave dielectric properties with a dielectric constant (ɛr) of 18.32, a Q × f of 109,200 GHz (where f = 9.5 GHz, is the resonant frequency) and a τf 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.