Multifunctional Er3+-Yb3+ codoped Gd2O3 nanocrystalline phosphor synthesized through optimized combustion route

This paper reports the synthesis of high upconversion luminescent Gd2O3: Er3+, Yb3+ nanophosphor through optimized combustion route using urea as a reducing agent. The paper also reports the first observation of upconversion emission bands extending upto the UV region (335, 366 and 380 nm) in Er3+-Yb3+ co-doped phosphor materials. The fuel to oxidizer ratio has been varied to obtain the maximum upconversion luminescence. Three high intensity bands are found at 408, 523-548 and 667 nm due to the (4)G(11/2) -> I-4(15/2), H-2(11/2), S-4(3/2) -> I-4(15/2) and F-4(9/2) -> I-4(15/2) transitions, respectively, along with the other bands. Input excitation power dependence has been studied for different transitions, and the saturation effect and decrease in the slope of different transitions at higher input pump power has been explained. Heat treatments of the samples show change in crystallite phase/size and relative upconversion luminescence intensities of blue, green and red bands. The color of the phosphor emission has shown to be tunable with change in the crystal structure as well as on excitation laser power and Er3+-Yb3+ concentration. The property of color tunability of the phosphor material has been used to record the fingerprint in different colors. Also, the future prospect of the nanocrystalline phosphor material as a sensor for temperature, using FIR method, has been explored.