Pure red upconversion emission from Yb3Al5O12 phase doped with high Er3+ concentration

Pure red upconversion luminescence was observed from Er3+ doped Yb3Al5O12 powder synthesized by sol-gel method. X-ray diffraction (XRD) and transmission electron microscopy (TEM) patterns revealed two phases Yb3Al5O12 and Yb2O3 coexisting as crystals. High resolution transmission electron microscopy (HRTEM) and energy dispersive spectroscopy (EDS) analysis showed that the luminescence was from Er3+ in Yb3Al5O12. High pure red emission was obtained in all three samples with the emission intensity ratios of red to green (R/G) being 78, 110 and 136 respectively. It was found that Yb3+ was a composition of the host Yb3Al5O12 rather than a doped ion and still played a sensitizing role and the R/G was in a positive variation with the ratio of Yb3+/Er3+. The possible mechanism can be ascribed to the resonant energy transfer 4F7/2(Er3+) + 4I11/2(Er3+) → 22F9/2(Er3+) caused by the high content of Yb3+.