Effect of different temperatures to remove reduction gas on the photoluminescence properties of Eu-doped Li2 (Ba1-x Srx )SiO4 phosphors.

In this study, Eu-doped Li2 (Ba1-x Srx )SiO4 powders (x = 0, 0.2, 0.4, and 0.6) were synthesized at 850°C in a reduction atmosphere (5% H2 + 95% N2 ) for a duration of 1 h using a solid-state reaction method. The reduction atmosphere was infused as the synthesis temperature reached 850°C, and was removed as the temperature dropped to 800-500°C. Li2 (Ba1-x Srx )SiO4 (or Li2 BaSiO4 ), (Ba,Sr)2 SiO4 (or BaSiO4 ), and Li4 SiO4 phases co-existed in the synthesized Eu-doped Li2 (Ba1-x Srx )SiO4 powders. A new finding was that the reduction atmosphere removing (RAR) temperature of the Li2 (Ba1-x Srx )SiO4 phosphors had a large effect on their photoluminescence excitation (PLE) and PL properties. Except for the 800°C-RAR-treated Li2 BaSiO4 phosphor, PLE spectra of all other Li2 (Ba1-x Srx )SiO4 phosphors had one broad emission band with two emission peaks centred at ~242 and ~283 nm; these PL spectra had one broad emission band with one emission peak centred at 502-514 nm. We showed that the 800°C-RAR-treated Li2 BaSiO4 phosphor emitted a red light and all other Li2 (Ba1-x Srx )SiO4 phosphors emitted a green light. Reasons for these results are discussed thoroughly.