Luminescence and Thermal-Quenching Properties of Red-Emitting Ca 2 Al 2 SiO 7 :Sm 3+ Phosphors

Ca 2 Al 2 SiO 7 : x .Sm 3+ ( x = 0.5, 1.0, 1.5, 2.0, 2.5, and 3.5 mol.%) (CAS: x .Sm 3+ ) phosphors were synthesized by a solid-state reaction technique. The structure, photoluminescence properties and thermal stability of phosphors were investigated in detail. Results of X-ray diffraction show that CAS: x .Sm 3+ materials have a single-phased tetragonal structure, and an expansion of the unit cell relates to the increasing of Sm 3+ concentration. Photoluminescence study displayed that the CAS: x .Sm 3+ phosphors reach the highest emission intensity at 1.5 mol.% Sm 3+ and achieved the luminescence quenching phenomenon a higher concentration. The dominant interaction mechanism of the concentration quenching process is determined due to the dipole–dipole interaction, and the critical transfer distance ( R c ) is 26.7 Å. The temperature dependence of photoluminescence spectra indicates that the Ca 2 Al 2 SiO 7 :Sm 3+ (1.5 mol.%) phosphor possess good thermal stability, and that the activation energy is around 0.12 eV (968 cm −1 ). Several characteristic vibrations in the 200–1000-cm −1 region were observed by Raman spectra, and the color chromaticity coordinates of the samples were also calculated and discussed.