Subsolidus phase relations and transparent conductors in the cadmium-indium-tin oxide system

Subsolidus phase relations have been determined in the CdO-InO_1.5-SnO₂ system at 1175°C. A cubic-bixbyite solution In_2-2x(Cd,Sn)_2xO₃ (0 < x < 0.34), a cubic spinel solution (1-x)CdIn₂O₄-xCd₂SnO₄ (0 < x < 0.75), and an orthorhombic-perovskite solution Cd_1-xSn_1-xIn_2xO₃ (0 < x < 0.045) having the GdFeO₃ structure have been discovered. The CdO phase field exists over a small range of InO_1.5 (<3%) and SnO₂ (<1%). Orthorhombic Cd₂SnO₄ (Sr₂PbO₄ structure) and rutile SnO₂ appear to be point compounds with negligible solubility. The vertical section between spinel CdIn₂O₄ and orthorhombic Cd₂SnO₄ was determined between 900° and 1175°C. The spinel phase field (1-x)CdIn₂O₄-xCd₂SnO₄ was found to extend between x = 0 and x = 0.75 at 1175°C or x = 0.78 at 900°C. All of the phases in this system appear to allow small excess quantities of the donors In and/or Sn (vs cation stoichiometry) which may be the source of the electrons that give these oxides their n-type character. The electrical and optical properties of bulk and thin-film specimens in this system are compared and contrasted with each other and the relative merits of each are assessed.