Upconversion luminescence of Y3Al5O12 (YAG):Yb3+, Tm3+ nanocrystals

YAG:Tm3+and YAG:Yb3+, Tm3+ nanocrystals were synthesized by a co-precipitation method using ammonium hydrogen carbonate as precipitator. Pure nanocrystals with a crystallite size of 40 nm were obtained after the precipitates were calcined at 800 °C. YAG:Tm3+ and YAG:Yb3+, Tm3+ powder compacts were excited by 796 and 940 nm, respectively. No upconversion emissions were observed either in YAG:Tm3+ and YAG:Yb3+, Tm3+ nanocrystals excited at 796 nm or in YAG:Tm3+ nanocrystals excited at 940 nm. However, the blue emission of YAG:Yb3+, Tm3+ nanocrystals excited by 940 nm was strong enough to be seen by the naked eyes. The emission intensity of this material was also influenced by Yb3+ concentration as well as the calcination temperature.