Photoluminescence of ZnS: Sm phosphor prepared in a reductive atmosphere

The characteristic emission of Sm+3 in Zn phosphors, fired in inert atmosphere (N2 gas) at various temperatures, was not detected. However, fired in reductive atmosphere at 1050°C, the characteristic Sm+3 emission appears, which exhibits intra-4f transitions at 570, 606 and 653 nm, as predicted from the 4G5/2 level to the 6H5/2, 6H7/2 and 6H9/2 levels. Sm doping favors the formation of hexagonal phase in host lattice of ZnS:Sm. The increase in hexagonal phase content will boost the overall photoluminescence emission intensity. The self-activated luminescence intensity increases with the increase in the amount of Sm doping up to a maximum at 0.2 mol% of Sm dopant. According to the phase identification by X-ray diffraction, the Sm2O2S phase favors the Sm+3 characteristic luminescence but it deteriorates in Sm2O3.