Influence of molybdenum substitution on the microwave dielectric properties of CaWO4 ceramic

Dielectric properties of Ca(W_1−xMo_x)₄ (x = 0, 0.02, 0.04, 0.06, 0.08) were investigated at microwave frequency. With the increase of MoO₃, the dielectric constant (ε _r ) increased slightly, the value of quality factor (Q × f ₀) increased considerably and reach the maximum of 79,919 GHz, and the temperature coefficient of resonant frequency (τ _f) shifted for the minus direction. The relationship between the dielectric properties and polarizability, packing fraction and the oxygen bond valence were discussed. The optimum results were obtained when x = 0.06, the dielectric properties are as follows: ε _r  = 10.22, Q × f ₀ = 79,919 GHz and τ _f = −40.39 ppm/°C.