Determination of strain, site occupancy, photoluminescent, and thermoluminescent-trapping parameters of Sm3+-doped NaSrB5O9 microstructures

摘要

Monoclinic NaSrB5O9:Sm3+ phosphors were synthesized by a conventional solid-state reaction method in air. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) studies revealed that the Sm3+ ions preferably occupy Sr2+ cation sites in the NaSrB5O9 host lattice. The doping-dependent crystallite size and lattice strain on the X-ray peak broadening of the NaSrB5O9:Sm3+ phosphor was determined by the Scherrer and Williamson-Hall (W-H) methods. Trigonally and tetrahedrally coordinated boron atoms in the phosphors were confirmed by confocal Raman analysis. Under near-UV excitation (402 nm), the NaSrB5O9:Sm3+ phosphors emitted reddish-orange light at 604 nm that corresponds to the (4)G(5/2)-> H-6(7/2) transition. The concentration quenching mechanism between the two Sm3+ ions within the host was proved to be the dipole-dipole interaction, and the critical distance was found to be 22.29 angstrom. The fitted luminescence decay curves in terms of a second-order exponential model suggest that the Sm3+ ions possess two different kinds of environments in the host lattice, which was supported by XPS analysis. The defects acting as trapping centers were investigated by thermoluminescence glow curves. The gamma-irradiated NaSrB5O9:Sm3+ phosphors show two major dosimetric glow peaks centered at about 188.83 and 378.66 degrees C, indicating two different kinds of trapping centers in the phosphors. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.