Dielectric properties of a new ceramic system (1 − x)Mg4Nb2O9–xCaTiO3 at microwave frequency

The microstructures and the microwave dielectric properties of the (1 − x)Mg4Nb2O9–xCaTiO3 ceramic system were investigated. In order to achieve a temperature-stable material, CaTiO3 (τf ∼ 800 ppm/°C) was chosen as a τf compensator and added to Mg4Nb2O9 (τf ∼ −70 ppm/°C) to form a two phase system. It was confirmed by the XRD and EDX analysis. By appropriately adjusting the x-value in the (1 − x)Mg4Nb2O9–xCaTiO3 ceramic system, near-zero τf value can be achieved. A new microwave dielectric material, 0.5Mg4Nb2O9–0.5CaTiO3 applicable in microwave devices is suggested and possesses the dielectric properties of a dielectric constant ɛr ∼ 24.8, a Q × f value ∼82,000 GHz (measured at 9.1 GHz) and a τf value ∼−0.3 ppm/°C.