Microwave dielectric properties of x(Mg0.7Zn0.3)0.95Co0.05TiO3–(1 − x)Ca0.8Sr0.2TiO3 ceramics with a zero temperature coefficient of resonant frequency

The microwave dielectric properties and microstructures of x(Mg0.7Zn0.3)0.95Co0.05TiO3–(1 − x)Ca0.8Sr0.2TiO3 ceramics prepared using a mixed oxide route were investigated. (Mg0.7Zn0.3)0.95Co0.05TiO3 has a dielectric constant (ɛr) of ∼20, a high-quality factor (Q × f) of ∼163,560 GHz, and a temperature coefficient of resonant frequency (τf) of ∼−65 ppm/°C. To produce a temperature-stable material, Ca0.8Sr0.2TiO3, which has a large positive τf value of 990 ppm/°C, was added to (Mg0.7Zn0.3)0.95Co0.05TiO3. The temperature coefficient of resonant frequency increased with increasing Ca0.8Sr0.2TiO3 content, going through zero at x = 0.95. The microwave dielectric material 0.95(Mg0.7Zn0.3)0.95Co0.05TiO3–0.05Ca0.8Sr0.2TiO3 has an excellent combination of microwave dielectric properties: ɛr ∼ 22.5, Q × f ∼ 90,000 (at 9 GHz), and τf ∼ 0.1 ppm/°C sinter at 1150 °C. It is proposed as a candidate material for ISM band components and GPS antennas.