Characterization of Structural Disorder in γ-Ga2O3

By H. Playford, A. Hannon, Matthew G. Tucker, D. Dawson, S. Ashbrook, Reza J. Kastiban, J. Sloan, Richard I. Walton. 2014

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Solvothermal oxidation of metallic gallium in monoethanolamine for 72 h at 240 °C yields a crystalline sample of γ-Ga2O3 (∼30 nm crystallites). While Rietveld refinement (cubic spinel structure, Fd3m; a = 8.23760(9) A) reveals that Ga occupies two pairs of octahedral and tetrahedral sites (ideal spinel and nonspinel), it provides no information about their local distribution, which cannot be statistical owing to the short Ga–Ga contacts produced if neighboring ideal spinel and nonspinel sites are simultaneously occupied. To create an atomistic model to reconcile this situation, a 6 × 6 × 6 supercell of the crystal structure is constructed and refined against neutron total scattering data using a reverse Monte Carlo (RMC) approach. This accounts well for the local as well as long-range structure and reveals significant local distortion in the octahedral sites that resembles the structure of thermodynamically stable β-Ga2O3. 71Ga solid-state NMR results reveal a octahedral:tetrahedral Ga ratio that is cons...

Subfields: Electronic, Optical and Magnetic Materials, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/b73f12731eb30ddd0836b44bbd86fe5bc939f3b3