Luminescence investigations of novel orange‐red fluorapatite KL aSr 3 ( PO 4 ) 3 F: Sm 3+ phosphors with high thermal stability

Single‐phase KL aSr 3 ( PO 4 ) 3 F: Sm 3+ phosphors with fluorapatite structure were prepared via high‐temperature solid‐state method in air atmosphere for the first time. The X‐ray diffraction, scanning electron microscope, diffuse reflectance spectra, photoluminescence spectra, and temperature‐dependent emission spectra, as well as lifetimes were measured to characterize the as‐prepared phosphors. Phase results indicated that KL aSr 3 ( PO 4 ) 3 F: Sm 3+ belongs to hexagonal system with a space group of P ‐6. Photoluminescence measurements showed the emission spectrum was composed of four sharp peaks at about 564, 602 (the strongest one), 646, and 702 nm, corresponding to the 4 G 5/2 ‐ 6 H J ( J =5/2, 7/2, 9/2, and 11/2) transitions of Sm 3+ ions. The optimum doping concentration of Sm 3+ ions was turned out to be 0.03 (mol), and the mechanism of energy transfer among Sm 3+ ions was considered to be dipole‐dipole interaction by using Dexter's theory. In addition, the critical distance R c for energy transfer among Sm 3+ ions were calculated to be 9.97 Å according to Blasse concentration quenching method. The selected KL a 0.97 Sr( PO 4 ) 3 F: 0.03Sm 3+ exhibited high thermal stability with an activation energy of 0.163 eV. Besides, the Commission International de l'Eclairage chromaticity coordinate of the phosphor were located in the orange‐reddish light region.