Fabrication and luminescent properties of Al2O3:Cr3+ microspheres via a microwave solvothermal route followed by heat treatment

AlOOH:Cr3+ powders were synthesized via a microwave solvothermal route at 433 K for 30 min and were used as the precursor and template for the preparation of gamma-Al2O3:Cr3+ by thermal transformation at 773 K for 2 h in air. The obtained gamma-Al2O3 based powders were microspheres with an average diameter about 1.9 mu m. Photoluminescence (PL) spectra showed that the Al2O3:Cr3+ particles presented a symmetric broad R band at 696 nm without appreciable splitting when excited at 462 nm. It is shown that the 0.04 mol% of doping concentration of Cr3+ ions in gamma-Al2O3:Cr3+ is optimum. According to Dexter's theory, the critical distance between Cr3+ ions for energy transfer was determined to be 47.54 angstrom. Based on the corresponding PL spectrum, full width at half maximum (FWHM) of Al2O3:Cr3+ (0.04 mol%) was calculated to be 3.35 nm. (c) 2012 Elsevier B.V. All rights reserved.