Synthesis, spectroscopic and luminescence properties of Ga-doped γ-Al2O3

Gallium-doped aluminum oxide (Al1-xGax)(2)O-3 with gamma-Al2O3 (spinel) structure has been synthesized by the precursor method using the formate Al1-xGax(OH)(HCOO)(2) as a precursor. The examination of Al1-xGax(OH)(HCOO)(2) (x = 0.0, 0.1, 0.2, 0.3, 0.4) was carried out by X-ray powder diffraction, Infrared, Raman spectroscopy and differential-thermal methods. The solid solutions gamma-(Al1-xGax)(2)O-3 with x <= 0.2 have been synthesized by thermolysis of precursors in helium atmosphere at 700 degrees C; they exhibit white-blue emission under UV excitation, whose intensity lowers with increasing dopant concentration. As an independent method, the DFT calculations confirmed thermodynamically the stability field of gamma-(Al1-xGax)(2)O-3 solid solutions and the NMR data on relative abundance of Al and Ga within the tetrahedral and octahedral sites in the metal sublaltice furthermore, the structural and thermodynamic properties of carbon-containing impurities within these compounds were suggested theoretically as possible models of luminescence emission centers. The experimentally observed Ga-dependent quenching of luminescence was explained using the competition between C2p and Ga4p states within the band gap of gamma-Al2O3. (C) 2019 Elsevier B.V. All rights reserved.