Quantum efficiency of europium emission from nanocrystalline powders of Lu2O3:E

Abstract

hree series of nanocrystalline powders ofLu2O3:Eu with Eu concentration varying from 0.05to 13% were prepared. All specimens were obtained through combustionsynthesis using urea or glycine as the fuel. The powders of the firstseries consisted of materials with crystallites about 13 nm in size andwere prepared with urea. For the next series of powders, made withglycine, the crystallites were about 30 nm in size. The powders of thethird series differed from those of the second one in that they wereco-doped with 1% of Ca. For the series made with urea the quantumefficiency was highest for 3% of Eu and never exceeded about 30%. Forglycine-prepared specimens the highest quantum efficiency was about 90%.Without the Ca co-doping such a value could be obtained for specimensdoped with 5% of Eu, while in the series co-doped with Ca 85-90% quantumefficiency could be maintained for all concentrations in the range3-10%. A significant number of OH groups were proved to be left in thefinal product obtained with urea. The low quantum efficiency of thesepowders is attributed to this effect. The results prove that properlyprepared nanocrystalline phosphors can produce luminescence efficiently.