Cation Distributions and Microwave Dielectric Properties of Spinel-Structured MgGa2O4 Ceramics

The Mg2+ and Ga3+ cation distributions in the MgGa2O4 lattice were characterized by the refinement of the crystal structure and the firing temperature dependence of microwave dielectric properties was described in this study. The crystal structure refinement of MgGa2O4 ceramics fired at different temperatures indicated that the degree of inversion x, which represents the Mg2+ and Ga3+ cation distributions in the 8(a) and 16(d) sites in (Mg1-xGax)[MgxGa2-x]O-4, slightly decreases from 0.88 to 0.84 with increasing firing temperature from 1500 to 1600 degrees C. This implies that the Mg2+ cation preferentially occupies the 8(a) site, i.e., the tetrahedral site, with increasing firing temperature. The dielectric constant (epsilon(r)) of the MgGa2O4 ceramics fired above 1520 degrees C was almost constant (epsilon(r) = 9.2), whereas their Q . f significantly increased from 92,000 to 298,000 GHz, depending on the firing temperature. Such an increase in the Q . f may be related to the Mg2+ and Ga3+ cation distributions in the MgGa2O4 lattice. (C) 2013 The Japan Society of Applied Physics