The photoluminescence and thermoluminescence properties of novel green long-lasting phosphorescence materials Ca_8Mg(SiO_4)4Cl_2:Eu~(2+),Nd~(3+)

摘要

The novel green long-lasting phosphorescence (LLP) material Ca_8Mg(SiO_4)_4Cl_2:Eu~(2+),Nd~(3+) was systematically investigated by means of photoluminescence (PL) excitation and emission, a thermal quenching process, long-lasting phosphorescent emission, decay curves, chromaticity and thermoluminescence (TL) spectra. It is clearly observed that there exist two distinguishable Eu sites, Eu_Ⅰ for 426-nm and EU_Ⅱ for 504-nm emissions, but only the green LLP appears at the Eu_Ⅱ site. The emissions for both PL and LLP are due to the 5d → 4f transitions. The green phosphorescence with the chromaticity coordination x = 0.196, y = 0.506 can still be observed in the dark for no less than 5 h by the naked eye. The results of TL show that Nd~(3+) ions induce the predominating band at 335 K, associated with the charge-trapping centers that are responsible for the appearance of intense green phosphorescence.