Cation Distribution of the Transparent Conductor and Spinel Oxide Solution Cd1+xIn2-2xSnxO4

The cation distribution in the transparent conducting oxide Cd_1+xIn_2-2xSn_xO₄ was investigated to determine if there is a correlation between structure and electronic properties. Combined Rietveld refinements of neutron and X-ray diffraction data and¹¹⁹Sn Mössbauer spectroscopic analysis were used to show that the cation distribution changed with x (0 ≤ x ≤ 0.7) from a primarily normal spinel (x=0) to an increasingly random spinel. CdIn₂O₄ quenched from 1175°C has an inversion parameter of 0.31 (i.e., (Cd_0.69In_0.31)^tet(In_1.69Cd_0.31)^octO₄). The inversion parameter decreases to 0.27 as the quench temperature is lowered from 1175°C to 1000°C. The decrease in inversion parameter with temperature correlates with an increase in optical gap from 3.0 eV to 3.3 eV for specimens prepared at 1175°C and 800°C, respectively. We show that this is a consequence of an increase in the fundamental band gap.