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

Three series of nanocrystalline powders of Lu 2 O 3 :Eu with Eu concentration varying from 0.05 to 13% were prepared. All specimens were obtained through combustion synthesis using urea or glycine as the fuel. The powders of the first series consisted of materials with crystallites about 13 nm in size and were prepared with urea. For the next series of powders, made with glycine, the crystallites were about 30 nm in size. The powders of the third series differed from those of the second one in that they were co-doped with 1% of Ca. For the series made with urea the quantum efficiency was highest for 3% of Eu and never exceeded about 30%. For glycine-prepared specimens the highest quantum efficiency was about 90%. Without the Ca co-doping such a value could be obtained for specimens doped with 5% of Eu, while in the series co-doped with Ca 85–90% quantum efficiency could be maintained for all concentrations in the range 3–10%. A significant number of OH groups were proved to be left in the final product obtained with urea. The low quantum efficiency of these powders is attributed to this effect. The results prove that properly prepared nanocrystalline phosphors can produce luminescence efficiently.