Up-Conversion Luminescence of Er3+/Pr3+/Yb3+ Co-doped LaNbO4 Phosphors

Er3+-Pr3+-Yb(3+)co-doped LaNbO4(LNO) phosphors were obtained by solid-state reaction and their up-conversion properties have been studied. The x-ray diffraction and Rietveld's refinement revealed no evidence of significant structural changes or secondary phases in the synthesized materials. According to the up-conversion measurements, the observed emissions are due to Er(3+)ions which are present as unintentional contaminant in the Pr(3+)doped and Pr3+-Yb(3+)co-doped systems. The intensity of all the bands was enhanced with increasing Yb(3+)concentration, and at 8%Yb(3+)a significant decrease of the green and red emissions was found due to the presence of cross-relaxation process between Er(3+)and Pr(3+)ions, mainly for green emissions because of the back energy transfer mechanisms from Er(3+)to Yb3+. The Commission Internationale de l'eclairage color coordinates of almost all samples were located in the green region, while for the LNO: Pr 0.1%-Yb8% phosphor they were located in the blue region. Red-Green-Blue phosphors were obtained from LaNbO4: Pr3+/Er3+/Yb(3+)systems using the pair of activators Pr3+/Er(3+)which is not commonly investigated in the literature.