A potential white light emitting cubic ZrO2:Dy3+, Li+ nano phosphors for solid state lighting applications

Abstract

This work details the structural and luminescence properties of Zr1-xO2: xDy3+ (x=0.005-0.025) and Zr1-x-yO2: xDy3+,yLi+ (x=0.015 and y=0.01-0.09) nano phosphors synthesized via self-propagating low temperature solution combustion method. The XRD pattern was refined by Rietveld refinement algorithm using Full Prof program and phosphors found that they were crystallized in the cubic phase of ZrO2. Further it has been observed that the crystallinity of the Dy3+-doped ZrO2 increased with Li+ co-dopant concentration. TEM micrographs revealed formation of spherical nano particles in the size 10–50nm. Photoluminescence properties of Dy3+ doped ZrO2 and Li+ co doped ZrO2:Dy3+ phosphors were examined. Enhancement of PL intensity was observed with Li+ doping. Furthermore, emission color is highly dependent on Li+ co-dopant concentration and photoluminescence spectra shows color tunable white luminescence of the phosphors under near UV excitation. Merely, by varying Li+ ions concentration white light was achieved. The color purity of the phosphors was confirmed using CIE co-ordinates and found to be (0.35, 0.33) for ZrO2:xDy3+,yLi+(x=1.5mol%) (y=5mol%) and (0.34, 0.33) for ZrO2:xDy3+,yLi+(x=1.5mol%) (y=7mol%) which is closer to pure white light region. Judd–Ofelt intensity parameters and radiative properties were studied for the prepared phosphors for better understanding of luminescence properties in prepared phosphors. This present work demonstrates effect of charge compensator on dopant ions and a simple and efficient method for the synthesis of novel color tunable white light emitting nano phosphors with enhanced brightness for white-LED applications.