Novel orange phosphate phosphors Sr19Mg2(PO4)14:Eu2+: crystal structure, luminescence and thermal quenching property investigation

The discovery of near-ultraviolet-excited orange-emitting phosphors is a major challenge in light-emitting diodes. Benefitting from highly condensed framework and abundant cation sites of beta-Ca-3(PO4)(2)-type compounds, a novel orange emitter, Sr19Mg2(PO4)(14):Eu2+, has been synthesized and investigated in this study. The structure and coordination environment around each cation were determined by Rietveld refinement for the first time. The optical bandgap was estimated by diffuse reflectance spectrum and the photoluminescence performance was studied systematically. The Sr19Mg2(PO4)(14):Eu2+ phosphor exhibited strong absorption in near-ultraviolet region, and emitted broad-band orange emission from 500 to 750 nm peaked at 620 nm. According to the Rietveld refinement result, photoluminescence and Gaussian fitting spectrum, it could be inferred the emission spectrum of Sr19Mg2(PO4)(14):Eu2+ came from three different Eu2+ luminescent centers which could be assigned to the different cation site. The different thermal stability of each luminescent center was also investigated and explained by the different Debye temperature (Theta(D)) calculated by average atomic displacement parameter; however, its integrated thermal stability still needs to be improved. All the results indicated Sr19Mg2(PO4)(14):Eu2+ may be applied as an alternative orange phosphor in WLEDs.