Intense red up-conversion luminescence and temperature sensing property of Yb/Er co-doped BaGdO phosphors.

In this study, intense red and extremely weak green up-conversion (UC) luminescence was obtained in BaGdO: x mol% Yb/y mol% Er phosphors under the excitations of 980 nm and 1550 nm. The corresponding maximum integrated intensity ratios of the red to green UC emissions are 50.3 and 158.7, respectively. The UC luminescence mechanisms upon different excitations were discussed. It was confirmed that two-photon and three-photon processes were responsible for both the red and green UC emissions excited at 980 nm and 1550 nm, respectively. The energy transfer efficiency from Er to Yb was calculated according to the fluorescence lifetime measurement under 1550 nm excitation. Temperature sensing based upon the thermally coupled energy levels H/S as well as thermally coupled Stark sublevels of F level of Er was investigated under the excitation of 980 nm. The maximum absolute sensitivities were respectively obtained to be 0.42% K at 573 K and 0.18% K at 298 K. Our results indicated that BaGdO: Yb/Er phosphors might be a kind of promising red UC phosphors with optical temperature measurement function.