Microwave dielectric properties of x(Mg_0.7Zn_0.3) _0.95Co_0.05TiO₃-(1 - X)Ca_0.8Sr _0.2TiO₃ ceramics with a zero temperature coefficient of resonant frequency

The microwave dielectric properties and microstructures of x(Mg _0.7Zn_0.3)_0.95Co_0.05TiO ₃-(1 - x)C_0.8Sr_0.2TiO₃ ceramics prepared using a mixed oxide route were investigated. (Mg_0.7Zn _0.3)_0.95Co_0.05TiO₃ has a dielectric constant (ε_r)of ∼20, a high-quality factor (Q×f)of ∼163,560 GHz, and a temperature coefficient of resonant frequency (t _f)of ∼-65 ppm/°C. To produce a temperature-stable material, Ca_0.8Sr_0.2TiO₃, which has a large positive t_f value of 990ppm/°C, was added to (Mg_0.7Zn _0.3)_0.95Co_0.05TiO₃. The temperature coefficient of resonant frequency increased with increasing Ca _0.8Sr_0.2TiO₃ content, going through zero at x = 0.95. The microwave dielectric material 0.95(Mg_0.7Zn _0.3)_0.95Co_0.05TiO₃-0D5Ca _0.8Sr_0.2TiO₃ has an excellent combination of microwave dielectric properties: ε_r ∼22.5, Q×f×90,000 (at 9GHz), and t_f ~0.1 ppm/°C sinter at 1150°C. It is proposed as a candidate material for ISM band components and GPS antennas.