Crystal structure and photoluminescence correlations in white emitting nanocrystalline ZrO2:Eu3+ phosphor: Effect of doping and annealing

White emitting nanocrystalline ZrO2:Eu3+ phosphors were synthesized by a simple precipitation route without using a capping agent. X-ray diffraction (XRD) study of ZrO2 and ZrO2:Eu3+samples revealed the presence of monoclinic and tetragonal phases. The monoclinic phase increases with increase in the annealing temperature while the tetragonal phase increases with increase in the concentration of Eu3+. This can be attributed to the presence of oxygen vacancy evolved when Zr4+ is replaced by Eu3+. Photoluminescence (PL) emission peaks of Eu3+ are observed at 591, 596, 606 and 613 nm on monitoring excitation wavelengths at 250, 286, 394 and 470 nm. The peaks at 591 and 606 nm were found to correlate with the tetragonal phase and those at 596 and 613 nm with the monoclinic phase. Intensities of these peaks are found to change as the crystal structure changes. The lifetime value corresponding to 591 nm peak increases with Eu3+ concentration at a particular heating temperature indicating increase of tetragonal phase with respect to monoclinic phase. The CIE co-ordinates of the doped samples were found to be close to that of white color (0.33, 0.33). The changes in the crystal structure of the doped samples due to doping and annealing did not affect the white color emission.