Cation distribution and oxygen parameter in CdGa2O4-CoGa2O4 solid solutions

Abstract

CdGa₂O₄, CoGa₂O₄ and six mixed spinels Cd_xCo_1−xGa₂O₄ (x = 0.1, 0.15, 0.25, 0.50, 0.75 and 0.85) were synthesized, in polycrystalline form, by solid state reaction at 1273 K between CdO and Ga₂O₃ impregnated with cobalt nitrate in the desired proportions. By means of X-ray diffraction analysis, the lattice parameter, a₀, oxygen parameter, u, and cation distribution for each spinel were determined. a₀ was found to increase continuously from 832.8 pm for x = 0 up to 860.1 pm for x = 1. The u-parameter also increases, along the same composition range, from 0.386 up to 0.392. Cation distribution in the mixed spinels was found to be dependent on composition. In particular, it is seen that the presence of Cd²⁺ enhances the relative octahedral preference of Co²⁺, and the tetrahedral preference of Ga³⁺.