Structural and luminescence properties of LaAlO3:Sm3+ nanophosphors synthesized via hydrothermal method

A sequence of orange-red light emitting LaAlO3: Sm3+ nanophosphors were prepared via hydrothermal technique. The phase identification, morphological studies, vibrational bands and photoluminescence characteristics of these nanophosphors were investigated. The X-ray diffraction proved that the nanophosphors crystallized in a single-phased rhombohedral crystal structure, the crystallite sizes were evaluated by Debye-Scherrer's relation and Williamson-Hall method and were detected in the range of 30–42 nm. Under the excitation at 407 nm, the photoluminescence peaks were noticed at 566, 600, 647 and 712 nm and were corresponding to 4G5/2 → 6H5/2, 4G5/2 → 6H7/2, 4G5/2 → 6H9/2 and 4G5/2 → 6H11/2 distinctive 4f-4f electronic transitions of Sm3+ ion, respectively and the most intense emission peak noticed at 600 nm. The luminescence intensity increased with an addition of Sm3+ concentration up to 6 mol% and then decreased for 8 mol% due to concentration quenching effect. The luminescence decay from 4G5/2 level of Sm3+ ions for all the prepared samples were measured and a strong dependence lifetime on the Sm3+ ion concentration was observed. The calculated CIE coordinate values indicate the orange-red emission from the Sm3+: LaAlO3 nanophosphors. All these results indicate that the present Sm3+: LaAlO3 nanophosphors might be suitable for orange-red light emission for near-ultraviolet excited white light emitting diode applications.