Effect of Synthesis Temperature on the Crystalline Structures and Photoluminescence Properties of the Green-light Ca_1.975Eu_0.025MgSi₂O₇ Phosphors

First of all, the Ca1.975Eu0.025MgSi2O7 powder was synthesized at the temperature range of 1150–1350 °C through the solid-state reaction method. The reduction atmosphere (5% H2 + 95% N2) was infused during the synthesis process, and it was removed as the temperature went to 800 °C. Synthesized at 1150 °C, the Ca2MgSi2O7, CaSiO3, and CaMgSiO4 phases coexisted, and the photoluminescence (PL) spectrum had only one broad emission band with centered wavelength of 475 nm (blue light), which was dominated by Eu2+-doped CaSiO3 and CaMgSiO4 phases. As Ca1.975Eu0.025MgSi2O7 powder was synthesized at 1350 °C, only the Ca2MgSi2O7 phase was observed, and Eu2+-doped Ca2MgSi2O7 phase would dominate the only one broad emission band with centered wavelength 529 nm (green light). Synthesized at 1200–1300 °C, the diffraction intensities of CaSiO3 and CaMgSiO4 phases decreased, and that of Ca2MgSi2O7 phase increased; their PL spectra could be broken into a combination of the PL spectra of 1150 °C- and 1350 °C-synthesized Ca1.975Eu0.025MgSi2O7 phosphors. The Ca1.975Eu0.025MgSi2O7 powder was also heated to 1350 °C, and the reduction atmosphere was removed as the temperature went to 1300–800 °C; only one broad emission band with centered wavelength 529 nm was found in these synthesized phosphors. When the reduction atmosphere removing temperature rose, because the concentration of Eu2+ ions decreased, both the emission intensity and decay time decreased.