A novel reddish-orange fluorapatite phosphor, La6-xBa4(SiO4)6F2: xSm3+ - Structure, luminescence and energy transfer properties

Samarium (III) doped fluorapatite phosphors La6-xBa4(SiO4)6F2: xSm3+ (LBSF: Sm3+) were synthesized for the first time, via the conventional high-temperature solid-state method in the air atmosphere. The samples were measured by X-ray diffraction, scanning electron microscopy and photoluminescence spectroscopy, i.e. emission and excitation spectra, as well as luminescence decay curves. The as-prepared samples can be excited in the range from 300-500 nm, centered at 404 nm. Photoluminescence measurements showed the emission spectra are composed of four sharp peaks characteristic of Sm3+ ions, at about 565, 603, 650 and 711 nm. The critical concentration for quenching of Sm3+ ions in the LBSF matrix is about 0.12 mol. According to the Dexter's theory, the mechanism of energy transfer between Sm3+ ions was considered to be dipole-quadrupole (d-q) interactions, with the critical distance calculated by the concentration quenching method to 9.89 Å. Moreover, the temperature-dependent emission spectra showed that the as-prepared phosphors have good thermal stability, with an activation energy of about 0.161 eV. Finally, according to the CIE coordination, the phosphor exhibited reddish-orange emission. Thanks to the mentioned favorable structural and optical properties, the Sm3+-doped La6Ba4(SiO4)6F2 phosphors have a potential application character, for the near ultraviolet white light emitting diodes.