A study of the effects of europium doping and calcination on the luminescence of titania phosphor materials

A range of europium-activated titania phosphors with the formula Ti1-3xEU4x O2 (x varying between 0.000397 and 0.00794) have been prepared, and the eff ects of europium content and titania phase on the luminescent properties ha ve been investigated. It has been demonstrated that the crystallization tem perature of the titania from the amorphous phase to the anatase phase is ra ised by addition of europium to the material. At the same time, the brightn ess of the emission is also increased as the europium content is raised to x = 0.00794. In addition, we have shown that calcination of the titania to form anatase or rutile reduces the brightness of the luminescence, and that as the temperature of calcination increases, the brightness falls. Eu-151 Mossbauer spectroscopy results have shown evidence for the presence of mult iple sites (by line broadening) as the europium concentration increases. Ex tra sites were also observed as the firing temperature was increased. In th e most extreme cases, the second sites are clearly visible as extra peaks. The Mossbauer spectrum for hydrothermally produced material (which showed n o luminescence) was relatively narrow, indicating that only one site was pr esent for the europium in this phase. These results indicate that the multi ple sites observed for the europium. in the calcined samples result from th e europium doping into both the anatase lattice and the brookite contaminan t lattice, and it is this latter material that is responsible for the lumin escence in the metastable crystalline titania.