Correlation between structural characteristics and microwave dielectric properties of scheelite Ca <inf>1-x</inf> Cd <inf>x</inf> MoO <inf>4</inf> solid solution

Ca 1-xCd 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 I4 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 ( 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 f of all these compositions were explained with oxygen bond valence. The well-sintered Ca 1-xCd xMoO 4 ceramics showed highly promising microwave dielectric properties (ε r = 8-10, Q × f = 46000-53000 GHz and f = -22 to -57 ppm/°C). © 2012 The American Ceramic Society.