Investigation of the relations between structure and microwave dielectric properties of divalent metal tungstate compounds

The microwave dielectric characteristics of AWO₄ (A = Mg, Zn, Mn, Ca, Sr, Ba) compounds and their relations with structure have been investigated as a function of A cations. Crystal structure was investigated by XRD; the structure changed from wolframite to scheelite with increasing size of A cation. Dielectric properties such as permittivity, temperature coefficient of resonant frequency (τ_f), and quality factors (Q × f) were found to be correlated with the size of A cations and the structure of compounds. Permittivity decreased with the size of A cations, and temperature coefficient of resonant frequency was correlated with unit cell volume. AWO₄ compounds are suitable for the applications of low-k dielectric materials; permittivity = 8-15, τ_f = -50 to -70, and Q × f = 60,000-70,000.