Frequency upconversion and downshifting emissions in solution combustion derived Yb3+, Pr3+ co-doped strontium aluminate nano-phosphor: A multi-modal phosphor

This paper reports the frequency upconversion and downshifting emissions from Yb3+, Pr3+ co-doped strontium aluminate nano-phosphor synthesized through solution combustion method. The structural measurements show nano-crystalline nature of the samples. The Fourier transform infrared measurements of the samples confirm the presence of different molecular species in the sample. The UV-vis-NIR spectrum of the sample shows absorption bands due to charge transfer band (CTB) and 4f-4f transition. The sample gives intense NIR upconversion emission centered at 854 nm on excitation with 976 nm laser. The emission intensity is optimum for 0.10 mol% concentration of Pr3+ ion. The power dependent emission intensity measurement indicates the involvement of two photons for the upconverted emissions. The sample also emits intense blue upconversion and red downshifting emissions on excitation with 532 nm laser. The emission intensity of the bands is enhanced significantly on annealing the samples at higher temperature. The large enhancement in the emission intensity is a combined effect of rare earth concentration, crystallinity and reduction in optical quenching centers. Thus, the multi-modal Yb3+, Pr3+ co-doped strontium aluminate nano-phosphor may be used for monochromatic source of NIR light, optical and display devices.