Effect of annealing and excitation wavelength on the downconversion photoluminescence of Sm3+ doped Y2O3 nano-crystalline phosphor

This paper reports the downconversion photoluminescence in Sm3+ doped Y2O3 nano-crystalline phosphor synthesized through solution combustion method. The structural characterization of the phosphor has been carried out using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques, which reveals its nano-crystalline nature. The particles size of the phosphor increases on annealing it, which has been confirmed by SEM measurement. The energy dispersive spectroscopic (EDS) measurement verifies the presence of Y, Sm and 0 elements in the phosphor. The Fourier transform infrared (FTIR) measurements show the presence of vibrational bands due to different groups in the phosphor. The photoluminescence excitation spectra of the phosphor show large number of excitation bands due to CTS and 4f-4f electronic transitions of Sm3+ ion. The Sm3+ doped Y2O3 phosphor emits an intense reddish orange color centered at 606 nm due to (4)G(5/2) -> H-6(7/2) transition upon excitation with different wavelengths such as 238, 363, 407, 424 and 464 nm. The photoluminescence intensity is observed larger for 407 nm excitation. Interestingly, the peaks observed in the emission match well with those present in the excitation upon 238 and 363 rim excitations in lower wavelength side. The photoluminescence intensity of the phosphor sample is enhanced upto three times after annealing the as-synthesized phosphor. The improvement in the photoluminescence intensity is due to an increase in crystallinity, particles size and reduction in optical quenching centers. The lifetime of the (4)G(5/2) level is found to be increased in the annealed phosphor. Thus, the Sm3+ doped Y2O3 nano-crystalline phosphor may be a suitable candidate for displays and photonic devices.