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

Abstract

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.

Eu2+ as the structural probe in the phase transformation of CMSA by site-selective occupancy and adjustable multimode white luminescence in Ca2(Mg0.5Al0.5)(Si1.5Al0.5O7) akermanite based on high-aluminum blast furnace slag

“…As the possibility of non-radiative transitions increases, the luminous intensity decreases. 37–39 The energy barriers Δ E 1 (0.26 eV) > Δ E 3 (0.23 eV) > Δ E 4 (0.22 eV) > Δ E 2 = 0.2 eV in the energy level diagram are higher than the value (0.198 eV) of Sr 2 La 0.8 Eu 0.2 SbO 6 , 40 indicating that the phosphor has good thermal stability. Joos et al proved the existence of Eu 2+ /Eu 3+ intervalence charge transfer (IVCT, electron transfer between two metal sites differing only in oxidation state) in Eu-doped CaF 2 /SrF 2 /BaF 2 and further pointed out that the low Eu 2+ /Eu 3+ IVCT state can cause the non-radiative decay of Eu 2+ .…”

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

“…As the RAR temperature was lower than 800°C, one broad‐band green emission centred at 502 nm was observed (Figure 3a), which was assigned to the 4f 7 →4f 6 5d 1 transition of Eu 2+ ions. [ 7 ] Figure 3(a) also shows that the maximum emission intensity of the PL spectra (PLmax) increased as RAR temperature decreased from 700 to 500°C and was saturated at 500°C. These results proved again that RAR temperature was the most important factor affecting intensities of emission spectra of Eu‐doped Li 2 (Ba 1‐x Sr x )SiO 4 phosphors.…”

“…The 370 and 373 nm UV LED was used as excitation source and samples with 80% silicone/20% Eu‐doped Li 2 (Ba 1‐x Sr x )SiO 4 phosphors (in weight) were used for measurements of PLQY values. [ 7 ] Errors on PLQY values were evaluated by calculating the standard deviation on the experimentally averaged PLQY values of 10 different measurements.…”

“…synthesized the Ca1.975Eu0.025MgSi 2 O 7 phosphor in a reduction atmosphere, and they found as the synthesis temperature rose from 1150 to 1350°C, the synthesized phosphors would emit blue (1150°C), blue‐cyan (1200°C), cyan (1250°C), cyan (1300°C), and green light (1350°C), respectively. [ 7 ] Yung et al . used nano‐scale ZnO particles with different diameters and lengths, and with a hexagonal prism structure, as a seed‐core material; tetraethyl orthosilicate was used to form a shell on the surface of the nano‐scale ZnO particles.…”

“…Previously, we found that the reduction atmosphere removing (RAR) temperature of the Ca 1.975 Eu 0.025 MgSi 2 O 7 phosphor would apparently affect the maximum emission intensities of their PLE and PL spectra. [ 7 ] This important new finding meant that there was no comparative research with which to discuss the effects of different RAR temperatures on the PLE and PL properties of the Li 2 (Ba 1‐x Sr x )SiO 4 phosphors. Therefore, we aimed to investigate the effect of different RAR temperatures on the PLE and PL properties of Li 2 (Ba 1‐x Sr x )SiO 4 phosphors.…”