The equilibrium phase diagram (1175 degreesC in air), solubility ranges and room temperature physical properties (electrical, optical) were established for the various n-type transparent conductors in the CdO-In2O3-SnO2 system. Extended solubility ranges were found to exist at constant Cd/Sn ratio for the bixbyite, spinel and orthorhombic perovskite phases. This is attributed to the isovalent and nearly size-matched nature of the co-substitution. Still larger solubility ranges were found for metastably-processed thin. films. Co-doped bixyite and spinel phases were found to be inherently off-stoichiometric with respect to cation composition, leading to self-doped n-type character, in bulk and films. A correlation was found between optimized conductivity in the various phases and the density of octahedral Cd, In and/or Sn species in their crystal structures. (C) 2003 Elsevier Science B.V. All rights reserved.