Dielectric properties and mixture behavior of y(Mg0.95Co0.05)4Ta2O9-(1-y)CaTiO3 ceramic system at microwave frequency

Abstract

The microstructures and the microwave dielectric properties of the y(Mg0.95Co0.05)4Ta2O9-(1-y)CaTiO3 ceramic system were investigated. In order to achieve a temperature coefficient of resonant frequency (τf) stable material, CaTiO3 (τf ∼ +800 ppm/°C) was chosen as a τf compensator and added to (Mg0.95Co0.05)4Ta2O9 (τf ∼ -59 ppm/°C) to form a two phase system. It was confirmed by the X-ray diffraction (XRD) and Energy dispersive X-ray (EDX) analysis. Although dielectric constant (εr) of the specimen could be boosted by increasing amount of CaTiO3, it would instead render a decrease in the quality factor (Q × f). The τf value is strongly correlated to the compositions and can be controlled through the existing phases. By appropriately adjusting the y-value in the y(Mg0.95Co0.05)4Ta2O9-(1-y)CaTiO3 ceramic system, near-zero τf value can be achieved. A new microwave dielectric material, 0.4(Mg0.95Co0.05)4Ta2O9-0.6CaTiO3 applicable in microwave devices are suggested and possesses the dielectric properties of a dielectric constant εr ∼ 25.78, a Q × f value ∼200,000 GHz and a τf value ∼ -4.69 ppm/°C. It is proposed as a very promising dielectric material for low-loss microwave and millimeter wave applications.