Photoluminescence properties of an orange-red LaSr2AlO5:Sm3+ phosphor prepared by the Pechini-type sol-gel process

LaSr2AlO5:Sm3+ phosphors were synthesized by the Pechini-type sol-gel process. The X-ray diffraction pattern revealed that a pure LaSr2AlO5 phase was obtained with a sintering temperature of 1200 °C. Microstructure characterization showed that the particles were spherical in shape with a mean size of 2.93 µm. Being a candidate orange/red emitting phosphor for orange and white light emitting diodes, LaSr2AlO5:Sm3+ could be effectively excited by both near-ultraviolet (NUV) and blue lights with typical f-f transitions of Sm3+ ions. The most intense emission corresponding to 4G5/2→6H7/2 (604 nm) could be achieved at the same Sm3+ concentration of 4 mol.%. The chromaticity coordinates of La0.96Sr2AlO5:0.04Sm3+ phosphor under the excitation of 407 and 458 nm were (0.57, 0.43) and (0.59, 0.38), respectively. Further study was carried out using Van Uitert's and Dexter's models. A consistent result was obtained that electric dipole-dipole interaction was dominant for the energy transfer among Sm3+ ions. The critical distance for energy transfer among Sm3+ ions in LaSr2AlO5 was calculated to be ca. 1.843 nm.

Graphical AbstractPL spectra of the La1–xSr2AlO5:xSm3+ (x=0.005–0.15) phosphors excited at 407 nm (a) and at 458 nm (b)Figure optionsDownload full-size imageDownload as PowerPoint slide