Samarium Luminescence Spectra of MgA12O4: Sm3+ Nanoparticles: Impact of Samarium Content and Temperature Treating

Nanopowders of samarium doped magnesium aluminate phosphors have been synthesized by a co-precipitation technique. Samarium concentration was varied in the range of 0.03, 0.1, 0.2, 0.3, 0.5, 1.0, 1.5 and 3 wt.%. It has been found that MgAl2O4 nanopowders are in the amorphous state when the samarium impurities are missing and the presence of samarium impurities even of the smallest concentration is the necessary condition for the formation of the crystalline spinel phase. Depending on the synthesis temperature (Ts) and samarium content, the nanoparticle size varies: from 5 nm to 6 nm at Ts = 700 °C and from 7 nm to 15 nm at Ts = 1000 °C. According to the X-ray phase analysis, it has been revealed that the nanoparticle sizes get smaller when the samarium concentration increases. Under the luminescence study, it has been found that there is an optimal set of the «samarium concentration - nanoparticle sizes“ parameters at which the luminescence intensity reaches an extreme value. The half-width of the most intensive 4G5/2 - 6H7/2 line became narrow under additional heat treatment. It evidences that Sm ions are situated in a near-surface layer in the just prepared nanoparticles and they get into inter-grain boundaries after additional annealing.