Frequency upconversion fluorescence studies of Er 3+/Yb 3+-codoped KNbO 3 phosphors

Abstract

Different concentrations of Er 3+ and Yb 3+ ions-doped potassium niobate (K 0.9NbO 3:Yb (x)Er (0.1 − x) for x = 0, 0.01, 0.05, 0.09 and 0.1) polycrystalline powder phosphors were prepared by the conventional solid state reaction method and were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Energy transfer and upconversion fluorescence properties of the Yb 3+ and Er 3+-codoped phosphors have been discussed. The XRD data has shown mono-phase for pure KNbO 3 while the doped samples represented additional phase formation. The SEM micrographs represented the rectangular crystal growth habit for the KNbO 3 phosphors when doped with 0.1 mol of Er 3+ ions. An intense green emission at 557 nm along with a red emission at 674 nm was observed when the doped samples were excited with 975 nm IR radiation. The upconversion mechanism has been discussed based on the excited state absorption and energy transfer mechanisms.