Blue shift of Tm3+ upconversion owing to Nd3+ in yttrium oxide powders pumped by pulsed red laser

► Synthesis of Tm3+ doped and Tm3+-Nd3+ co-doped Y2O3 powders by combustion synthesis. ► Tm3+:Y2O3 exhibits emission at 450 nm when irradiated by a pulsed laser at 690 nm. ► The emission shifts to 480 nm when Nd3+:Tm3+:Y2O3 is exposed to the same laser. ► When the laser is tuned to 680 nm, the blue shift effect is not observed. ► The shifting effect is explained based on energy transfer involving Tm3+ and Nd3+.