Microwave dielectric properties of (1 - X)(Mg _0.95Ni _0.05)TiO ₃-x(Ca _0.8Sr _0.2)TiO ₃ ceramic system with near-zero temperature coefficient

The microwave dielectric properties of the (1 - x)(Mg _0.95Ni _0.05)TiO ₃-x(Ca _0.8Sr _0.2)TiO ₃ ceramic system prepared by mixed oxide route have been investigated. The crystal structures and the microstructures of the ceramics were characterized by means X-ray and scanning electron microscopy. The microwave dielectric properties are strongly related to the density and matrix of the specimen. Combination of (Mg _0.95Ni _0.05)TiO ₃ (ilmenite-type structure) and (Ca _0.8Sr _0.2)TiO ₃ (perovskite-structured) forms a two-phase system and leads to a near-zero temperature coefficient (τ _f). With increasing x, the quality factor (Q × f) decreased and dielectric constant (ε _r) increased. A new microwave dielectric material 0.95(Mg _0.95Ni _0.05)TiO ₃-0.05(Ca _0.8Sr _0.2)TiO ₃, possessing excellent microwave dielectric properties with a dielectric constant (ε _r) of 21.68, a quality factor (Q × f) of 94,000 (GHz) and a temperature coefficient (τ _f) of approximately -5.2 ppm/°C at 1275°C for 4 h, is proposed as a suitable candidate material for microwave applications requiring low dielectric loss.