Gd3+ ion induced UV upconversion emission and temperature sensing in Tm3+/Yb3+:Y2O3 phosphor

Cubic phase Tm3+/Yb3+:Y2O3 and Tm3+/Yb3+/Gd3+:Y2O3 phosphors were prepared by low temperature combustion technique for upconversion emission in UV–visible range. The 980 nm excitation has generated UV emission at 314 nm in tridoped phosphor due to the energy transfer from Tm3+ to Gd3+ ion. Characteristic emission bands from Tm3+ are also observed in both the phosphors. Thermally coupled Stark sublevels 1G4(a) (476 nm) and 1G4(b) (488 nm) of Tm3+ ion were utilised for optical thermometry using fluorescent intensity ratio (FIR) method. The result shows that maximum absolute sensitivity in tridoped phosphor is observed to be 1.33 × 10−3 K−1 at 298 K. Moreover, temperature rise of phosphor at various pump power densities was also measured and it is estimated to achieve 407 K at the pump power density of 38.46 W/cm2.