Co-doping effect of monovalent alkali metals on optical properties of CeO2:Eu nanophosphor prepared by spray pyrolysis and application for preparing pearlescent pigments with red emission

Abstract

Nano-sized CeO2:Eu/M (M = alkali metal) red phosphor was synthesized by spray pyrolysis. Three alkali metals (Li, Na and K) were introduced to find the most suitable codopant in terms of luminescent intensity and nano-sized phosphor synthesis. The emission intensity of CeO2:Eu was largely improved about twice or more by the codoping of monovalent alkali metal due to the charge compensation effect and the improvement of crystallinity. The emission enhancement was largest when Na was codoped and the emission intensity showed a linear relationship with the crystallite size regardless of the kind of alkali metal. The particle size increased with the codoping of alkali metals, but the resulting phosphor still had a nanosize of 100–200nm. When Na was used, the resulting powders exhibited less aggregation characteristics compared with Li and K. Thus, it was concluded that the Na codoping was most suitable for the synthesis of nano-sized CeO2:Eu/M phosphors with improved luminescence. The prepared CeO2:Eu/Na nanoparticles were coated on the surface of commercially available pearl pigment. The resulting pearlescent pigment was found to have sufficient red emission to be visible to the naked eye when illuminated by an LED UV lamp.