Intrinsic factors affecting the microwave dielectric properties of Mg2Ti1-x(Mg1/3Sb2/3)XO4 ceramics

The effect of crystal structure on the microwave dielectric properties of Mg2Ti1-x(Mg1/3Sb2/3)(x)O-4 (0.025 <= x <= 0.15) ceramics was investigated. A single phase having a cubic inverse spinel structure formed over the entire range of compositions, in specimens sintered at 1450 degrees C for 4 h. The structural characteristics of these ceramics were quantitatively evaluated by applying the Rietveld refinement method to the X-ray diffraction data. The largest bond strength between the cation and the oxygen ion and hence the highest quality factor (Qf) of the specimens were obtained at x=0.05. Although the ionic polarizability (3.29 angstrom 3) of (Mg1/3Sb2/3)(4+) was larger than that (2.93 angstrom(3)) of Ti4+, the dielectric constant (K) of the specimens decreased owing to the decrease of rattling effect with increasing x. In addition, the temperature coefficient of resonant frequency (TCF) decreased with decreasing K values. Typically, a high Qf value of 229,000 GHz was obtained for the specimens with x=0.05. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.