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

The microstructures and the microwave dielectric properties of the y(Mg0.95Co0.05)(4)Ta2O9-(1-y)CaTiO3 ceramic system were investigated. In order to achieve a temperature coefficient of resonant frequency (tau(f)) stable material, CaTiO3 (tau(f) similar to +800 ppm/degrees C) was chosen as a tau(f) compensator and added to (Mg0.95Co0.05)(4)Ta2O9 (tau(f) similar to -59 ppm/degrees 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 (epsilon(r)) of the specimen could be boosted by increasing amount of CaTiO3, it would instead render a decrease in the quality factor (Q x f). The tau(f) 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)(4)Ta2O9-(1-y)CaTiO3 ceramic system, near-zero tau(f) value can be achieved. A new microwave dielectric material, 0.4(Mg0.95Co0.05)(4)Ta2O9-0.6CaTiO(3) applicable in microwave devices are suggested and possesses the dielectric properties of a dielectric constant epsilon(r) similar to 25.78, a Q x f value similar to 200,000 GHz and a tau(f) value similar to -4.69 ppm/degrees C. It is proposed as a very promising dielectric material for low-loss microwave and millimeter wave applications. (C) 2015 Elsevier B.V. All rights reserved.