Microwave dielectric properties of scheelite (A = Ca, Sr, Ba) and wolframite (A = Mg, Zn, Mn) AMoO4 compounds

The microwave dielectric properties of scheelite (A = Ca, Sr, Ba) and wolframite (A = Mg, Mn, Zn) AMoO(4) compounds and their relations with structure have been examined using a network analyzer and X-ray powder diffraction. The Mo ion polarizability has been also investigated from AMoO(4) compounds using a least square refinement technique in conjunction with the Clausius-Mosotti equation. It was found that dielectric properties such as dielectric constant, temperature coefficient of resonant frequency, and quality factor were found to be correlated with the size of A-cations and the structure of compounds. The well sintered AMoO(4) samples (>95% of theoretical density) exhibited dielectric constant of 7-11, quality factor of 37,000-90,000 GHz and temperature coefficient of resonant frequency of -57 to -87 ppm/degrees C, respectively. These investigations showed that AMoO(4) ceramic could be selected as a possible candidate for microwave dielectric ceramics because of its low dielectric constant and high quality factor. (C) 2006 Elsevier Ltd. All rights reserved.