Effect of crystalline ordering on the luminescent properties of Eu3+-doped aluminum oxide nanophosphors

Abstract

Al2O3:Eu3+ nanophosphors were synthesized by the microwave assisted solvothermal technique. The structural and photoluminescence characteristics of alumina powders doped with 6.4 ​at.%, 7.5 ​at.%, 9.5 ​at.% and 13 ​at.% Eu, calcined at 900 ​°C, 1000 ​°C, 1100 ​°C and 1200 ​°C for 3 ​h, were investigated by X-ray diffraction, and reflectance, photoluminescent and X-ray fluorescence spectroscopies. The effects of the calcination temperature on the structure and, in turn of it on the photoluminescence properties are investigated. Luminescent decays curves were measured for the emission ascribed to the 5D0-7F2 transition in all the samples and a non-exponential behavior is observed. An increase in the average lifetime correlates well with the formation of the EuAlO3 perovskite phase as the calcination temperature increases. Judd-Ofelt analyses were performed andsome additional quantities were derived from them such as the radiative and nonradiative transition rates and the emission quantum efficiency. The decrease in the Ω2 parameter value as the calcination temperature increases is compatible with a higher symmetry around the Eu3+ site as well as with a reduction in the Eu3+ covalence bonding within this ion into EuAlO3 perovskite.