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

Effects of Composition Variations on the Crystalline Phases and Photoluminescence Properties of Ca2+x MgSi2Eu0.025O7+x Phosphors

A solid-state reaction method was used to synthesize Ca_2+x MgSi₂Eu_0.025O_7+x (x = 0-1.0) powders in the air atmosphere and in a reduction atmosphere (95% N₂ + 5% H₂) at 1350 °C and 4 h, and the reduction atmosphere was removed at 800 °C. Only the Ca₂MgSi₂O₇ phase was found in the XRD pattern of the synthesized Ca₂MgSi₂Eu_0.025O₇ powder. The first important discovery was that when the x value of Ca_2+x MgSi₂Eu_0.025O_7+x powders was increased from 0.2 to 0.8, both Ca₂MgSi₂O₇ and Ca₃MgSi₂O₈ phases coexisted in the synthesized Ca_2+x MgSi₂Eu_0.025O_7+x powders, and the diffraction intensity of the Ca₂MgSi₂O₇ (Ca₃MgSi₂O₈) phase decreased (increased) with the x value. The second important discovery was that the Ca₂MgSi₂Eu_0.025O₇ phosphor exhibited stronger photoluminescence excitation (PLE), photoluminescence (PL), and decay curve properties than the Ca_2.2MgSi₂Eu_0.025O_7.2 phosphor, and the Ca₃MgSi₂Eu_0.025O₈ phosphor exhibited stronger PLE, PL, and decay curve properties than the Ca_2+x MgSi₂Eu_0.025O_7+x phosphors for x = 0.4, 0.6, and 0.8. For x = 0.2-0.8, the PL spectra of the Ca_2+x MgSi₂Eu_0.025O_7+x phosphors were a combination of the PL spectra of Ca₂MgSi₂Eu_0.025O₇ and Ca₃MgSi₂Eu_0.025O₈ phosphors. The third important discovery was that as the x value was increased, the maximum emission peak wavelengths of the Ca_2+x MgSi₂Eu_0.025O_7+x phosphors shifted to a lower value, the maximum emission intensity of the PL spectra increased, and the emission light changed from green and cyan to blue.