A fluorite-related phase of Gd2O3, with a tetragonal unit cell of a = 5.65 Angstrom and c = 5.37 Angstrom, was attained in this study. The new phase was found either in a thin Gd2O3 film (similar to 18 Angstrom), which was epitaxially grown on GaAs(100). or in a disordered (by mild Ne+-ion sputtering) and recrystallized (by UHV annealing) thin cubic alpha -Gd2O3 film. The structural characteristics of the new oxide films were studied using in situ reflection high-energy electron diffraction, secondary-electron imaging, and single-crystal x-ray diffraction.