Temperature compensating microwave dielectric based on the (Mg_0.97Co_0.03)₂(Ti_0.95Sn_0.05)O₄–CaTiO₃ ceramic system

The microstructures and the microwave dielectric properties of the (1 − x)(Mg_0.97Co_0.03)₂(Ti_0.95Sn_0.05)O₄–xCaTiO₃ ceramic system prepared by the conventional solid-state route were investigated. (Mg_0.97Co_0.03)₂(Ti_0.95Sn_0.05)O₄ possesses high dielectric constant (ε_r = 14.23), high quality factor (Q × f = 188,760 GHz), and negative τ_f value (τ_f = −55.48 ppm/°C) at 1,390 °C for 4 h. In order to achieve a temperature stable material, CaTiO₃, having a large positive τ_f value of 800 ppm/°C, was added to (Mg_0.97Co_0.03)₂(Ti_0.95Sn_0.05)O₄. Two phase system was confirmed by the X-ray diffraction patterns and the energy-dispersive X-ray analysis. Although the ε_r of the specimen could be boosted by increasing amount of CaTiO₃, it would instead render a decrease in the Q × f. By appropriately adjusting the x value in the (1 − x)(Mg_0.97Co_0.03)₂(Ti_0.95Sn_0.05)O₄–xCaTiO₃ ceramic system, zero τ_f value can be achieved. A new microwave dielectric material, 0.91(Mg_0.97Co_0.03)₂(Ti_0.95Sn_0.05)O₄–0.09CaTiO₃ ceramic sintered at 1,390 °C had optimal dielectric properties (ε_r = 18.13, Q × f = 87,562 GHz, τ_f = 3.75 ppm/°C) which satisfied microwave applications in resonators, filters and antenna substrates.