A red phosphor (Y2O3:Eu3+), a green phosphor (LaPO4:(Ce3+):Tb3+) and a blue phosphor (BaMgAl10O17:Eu2+) have been modified using colloidal suspensions containing La2O3 and Al2O3, Y2O3 nano particles, respectively. The zeta potential of the matrix phosphors and the nano particles were measured in determining the surface modification conditions. The optimum adsorption (pH) conditions, based upon the zeta potential-pH relations, were applied for the maximum electrostatic interaction between the oxide phosphors and nano particles. The microstructural morphologies of the oxide phosphors coated with the nano-sized oxide particles were observed by SEM images. The photoluminescence behavior and the color coordinates (chromaticity diagrams) of the oxide phosphors modified with nano particles were examined to compare with those of the raw phosphors.

Keywords: phosphors; surface modification; nano particles; isoelectric point (IEP)