Correlation Between Structural Characteristics and Microwave Dielectric Properties of Scheelite Ca_(1-x)Cd_xMoO_4 Solid Solution

摘要

Ca_(1-x)Cd_xMoO_4 (x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) ceramics were prepared by solid-state reaction method. Tetragonal scheelite structure with 14_1/a space group was observed in all these compositions. Microwave dielectric properties such as quality factor (Q × f), dielectric constant (ε_r), and temperature coefficient of resonant frequency (T_f) were measured in the microwave frequency range. Rietveld refinement was performed on all these compositions and bond valences of A-, B-site cation, and oxygen were calculated. Influence of these structural parameters on the microwave dielectric properties was examined. Q × f was correlated with the average covalence of A-, B-site cations. The variation in ε_r was explained with ionic polarizability of Cd~(+2) ions. The deviation of observed polarizability from theoretical polarizability and T_f of all these compositions were explained with oxygen bond valence. The well-sintered Ca_(1-x)Cd_xMoO_4 ceramics showed highly promising microwave dielectric properties (ε_r = 8-10, Q × f= 46000 -53000 GHz and T_f = -22 to -57 ppm/℃).