Radiative energy transfer in ZnAl2O4:0.1% Ce3+, x% Eu3+ nanophosphor synthesized by sol-gel process

Zinc aluminate (ZnAl2O4) hosts and 0.1% Ce3+, x% Eu3+ co-activated ZnAl2O4 phosphor were successfully prepared at a relatively low temperature (similar to 80 degrees C) using the sol-gel method. The co-activator (Eu3+) concentration was varied in the range of 0 <= x <= 2 mol%, while the 0.1% Ce3+ was kept constant. The X-ray diffraction (XRD) data revealed that all annealed samples consisted of the pure cubic ZnAl2O4 structure. The estimated crystallite size was in the range of 18-21 nm in diameter. The results showed that the full width at half maximum (FWHM) increased with the increase in Eu3+ mol%, which suggested a decrease in particle size. The nanopowder microstructure revealed that the material consisted of non-uniform sizes and the loss of lattice fringes as the Eu3+ concentration was increased suggested the increase in strain or disorder. The photoluminescence (PL) results showed that the host, activated and co-activated nanophosphor emitted at different wavelengths. The peak shifts suggested that the luminescence might originate either from the defects in the host, Ce3+ or Eu3+ ions. The incorporation of the co-activator (Eu3+) at higher concentration resulted in radiative energy transfer from Ce3+ -> Eu3+. The CIE colour coordinates showed a shift from the blue to orange region as the Eu3+ concentration was increased. (C) 2015 Elsevier B.V. All rights reserved.