Effect of the octahedral bond valence on microwave dielectric properties of (1-x)Al0.5Ta0.5O2-xMg0.33Ta0.67O2 ceramics

Abstract

The dependence of the octahedral bond valence on the microwave dielectric properties of (1-x)Al0.5Ta0.5O2-xMg(0.33)Ta(0.67) O-2 (0.6 <= x <= 1.0) ceramics was investigated. As x increased beyond 0.6, (1-x)Al0.5Ta0.5O2-xMg(0.33)Ta(0.67)O(2) transformed into a tetragonal structure. As x increased, the dielectric constant (epsilon(r)) increased from 25.8 to 27.4 due to an increase in ionic polarizability, and the discrepancy between the observed dielectric polarizabilities (alpha(obs.)) and the theoretical ones (alpha(theo.)) increased from 4.02% to 4.68% with the decrease of the octahedral bond valence from 3.759 to 3.726 due to the increase of the unit cell volume. The temperature coefficients of the resonant frequencies (tau(f)) were found to depend on the octahedral bond valence and dielectric mixing rule.