Up-conversion luminescence of Er3+ doped and Er3+/Yb3+ co-doped YTaO4
Up-conversion luminescence of Er^3＋ doped and Er^3＋/Yb^3＋ co-doped YTaO4

The synthesis and up-conversion luminescent properties of YTaO4:Er3+ and YTaO4:Er3+/Yb3+ are reported for the first time. According to the measurement results of up-conversion spectra, Yb3+ co-doping can remarkably enhance the green (2H11/2/4S3/2→4I15/2) and red (4F9/2→4I15/2) emissions, but depress the infrared emission (4I9/2→4I15/2). With the increase of the Yb3+ concentration, the intensity of green emission increases, after that, when the Yb3+ concentration increases continuously, the intensity of green emission decreases, while those of the red and infrared emissions increase and decrease alternately. In addition, the up-conversion mechanisms of Er3+ doped and Er3+/Yb3+ co-doped YTaO4 are also discussed. It is found that the transform of up-conversion mechanism from two-step energy transfer to cooperating sensitization takes place when Yb3+ concentration is increased up to 12 mol%. With the further increase of Yb3+ concentration, the energy-back-transfer gradually becomes the dominant up-conversion mechanism, which results in the quenching of the green emission and slight increasing of the red and infrared emissions. Supported by the National Natural Science Foundation of China (Grant No. 10374011)