J. Ovenstone et al., A study of the effects of europium doping and calcination on the luminescence of titania phosphor materials, J PHYS CH B, 105(30), 2001, pp. 7170-7177
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.