Structure of β-AgGaO2; ternary I-III-VI2 oxide semiconductor with a wurtzite-derived structure

The structure of the wurtzite-derived beta-AgGaO2 was refined by Rietveld analysis of high-resolution powder diffraction data obtained using synchrotron X-ray radiation. The space group of the crystal is Pna2(1) with lattice parameters of a(0) = 5.56175 angstrom, b(0) = 7.14749 angstrom, and c(0) = 5.46875 angstrom. The deviation of O-Ag-O and M-O-M bond angles from the regular tetrahedral angle of 109.5 degrees was very large at similar to 8 degrees and similar to 11 degrees, respectively. The electronic structure of beta-AgGaO2 is discussed based on its structure, and the indirect band gap of beta-AgGaO2 was related to significant tetrahedral distortion. Although beta-AgGaO2 decomposes into metallic silver and Ga2O3 at a high temperature in any atmosphere, beta-AgGaO2 is stable up to 690 degrees C under an O-2 atmosphere. No direct transformation from the wurtzite-derived phase to a delafossite phase occurs in beta-AgGaO2. (C) 2014 Elsevier Inc. All rights reserved.