Subsolidus phase relationships in the ZnO-In₂O ₃-SnO₂ system

The subsolidus phase relationships in the ZnO-InO_1.5-SnO ₂ system were investigated at 1275°C using X-ray diffraction. Each of the end members of the ternary diagram is a transparent conducting oxide. There are two substantial solid solutions in the ternary phase space, the bixbyite solid solution In_2-2xZn_xSn_xO ₃ (x=0-0.40), and the indium substituted zinc stannate spinel, Zn_(2-x)Sn_(1-x)In_2xO₄ (x=0-0.45). The bixbyite solid solution is an outstanding TCO, whereas the spinel is only moderately conducting. Along the ZnO-InO_1.5 binary, there is a series of transparent conducting homologous compounds (ZnO)_k·In ₂O₃ (where k=3, 4, 5, 6, 7, 9, 11). Within ternary phase space, these homologous compounds were found to exhibit negligible Sn solubility, and were always found to be compatible with the spinel. Equilibrium was difficult to achieve in the phase space between the homologous series compounds and the spinel, owing to sluggish kinetics. A procedure involving mixtures of prereacted spinel and the Zn₁₁In₂O ₁₄ (k=11) compound was developed, which allowed for more rapid approach to thermodynamic equilibrium, thereby allowing for the establishment of phase relationships near the ZnO corner of the phase diagram.