Intrinsic defect processes in bixbyite sesquioxides

Atomic scale simulation techniques have been employed to study the intrinsic defect processes of a range of bixbyite sesquioxides using a transferable set of interatomic potentials. The efficacy of the approach is demonstrated through comparison of the predictions to previous experimental and theoretical (density functional theory) results. The aim here is to provide data that can be used as a basis for further structural optimizations targeting the use of mixed bixbyite sesquioxides as buffer layers for the fabrication of epitaxically coated, high-temperature superconductors on different substrates. The internal energies for the three possible intrinsic defect reactions (Schottky, cation Frenkel and oxygen Frenkel) have been calculated with regard to the application of these oxides for scintillator radiation detectors. The lowest energy intrinsic process is the oxygen Frenkel for all the bixbyite sesquioxides considered. Surprisingly, the oxygen Frenkel energy does not depend greatly on the host cation radius. The implication of this result is that the lowest energy intrinsic defect occurs on the oxygen sublattice and therefore will be most likely to serve as electron and hole traps. These traps are important for the scintillation properties of bixbyite sesquioxides as they act as non-radiative centers reducing the efficiency of scintillator materials. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.