Bond Lengths in the α-Ga2O3 Structure and the High-Pressure Phase of Ga2−xFexO3

The crystal structure of α-Ga2O3, which is isostructural with α-corundum, has been refined from single-crystal x-ray diffraction data. The bond lengths have been determined to an accuracy of about 0.01 Å. The bond lengths in the GaO6 octahedron are 2.077 and 1.921 Å. The short Ga–O distance corresponds to the oxygens forming the unshared face of the octahedron, whereas the long one corresponds to the shared face. Under high pressure and high temperature Ga2−xFexO3 undergoes a phase transition. The room-temperature, room-pressure phase is orthorhombic. In this structure the gallium ions have coordination numbers 4 and 6 while the iron ions have coordination number 6 only. The high-temperature, high-pressure phase is isostructural with α-corundum so that all cations have coordination number 6.