Effects of Crystal Structure on the Microwave Dielectric Properties of ABO(4) (A = Ni, Mg, Zn and B = Mo, W) Ceramics

The dependence of microwave dielectric properties on the crystal structure, bond character, and electronic characteristics of AMoO(4) and AWO(4) (A = Ni, Mg, Zn) ceramics was investigated. The dielectric constant (K) of specimens was principally affected by the dielectric polarizabilities, molar volume, and electronic oxide polarizabilities. MgMoO4 and AWO(4) (A = Ni, Mg, Zn) display a single phase monoclinic wolframite structure, whereas ZnMoO4 is a single phase triclinic wolframite structure. The quality factor (Qf) of AWO(4) was higher than that of AMoO(4) (A = Mg, Zn); these results were attributed to the packing fraction due to effective ionic size. The temperature coefficient of the resonant frequency (TCF) of the specimens was dependent on the cations' bond valence between the cation and oxygen ions. This suggests the ability to tailor ABO(4) microwave K, Qf, and TCF via ionic design rules.