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 degrees C. Microstructure characterization showed that the particles were spherical in shape with a mean size of 2.93 mu m. 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 (4)G(5/2)-> H-6(7/2)(604 nm) could be achieved at the same Sm3+ concentration of 4 mol.%. The chromaticity coordinates of La0.96Sr2AlO5:0.04Sm(3+) 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.