The photoluminescence of SrAl_2O_4: Sm phosphors

摘要

A red emitting SrAl_2O_4: Sm phosphor powder was synthesized by the solid-state method. The phosphor showed Sm~(3+) emission when fired in a reducing atmosphere at 1200 deg C. The intraion emission spectra of Sm~(3+) (~4G_(5/2) => ~4H_(5/2)) indicates Sm~(3+) + hv => Sm~(2+) + h_(VB) reaction to occur with intense emission lines located at 562, 596 and 643 nm. Results indicate that fluxing agents such as LiF and B_2O_3 play an important role in the photoluminescence (PL) emission intensity of SrAl_2O_4 powders. Also an increased content of the hexagonal phase in the SrAl_2O_4 powder boosts the PL intensity. The emission intensity becomes stronger as the firing temperature increases from 600 to 1200 deg C. SrAl_2O_4: Sm shows the maximum PL intensity at 10 wt percent of B_2O_3 addition. The B_2O_3 addition affects the spacing of the (211) planes but not the (220) and (211) planes. This derives from B~(3+) ion replacing the Al~(3+) ion in the (211) plane and causing shrinkage of the crystal lattice, which induces crystal defects and hence produces a stronger PL intensity.