Er3+ doped Y2O3 phosphor was prepared by the solution combustion method and

characterized using powder X-ray diffraction and energy-dispersive analysis of Xray

mapping studies. Room-temperature near-infrared to green up-conversion

emissions in the region of 520 to 580nm {(2H11/2, 4S3/2) →4I15/2} and red upconversion

emissions in the region of 650 to 700nm (4F9/2 →4I15/2) of Er3+ ions

were observed upon direct excitation to the 4I11/2 level using ~972nm laser radiation

of nanosecond pulses. The possible mechanisms for the up-conversion processes

were discussed on the basis of the energy level scheme, the pump power

dependence as well as based on the temporal evolution. The excited state

absorption was observed to be the dominant mechanism for the up-conversion

process. The Y2O3:Er exhibited one thermally stimulated luminescence peak

around 367C. Electron spin resonance studies were carried out to study the defect

centres induced in the phosphor by gamma irradiation and also to identify the

centres responsible for the thermally stimulated luminescence peak. Roomtemperature

electron spin resonance spectrum of irradiated phosphor appeared to

be a superposition of at least three distinct centres. One of them (centre I) with

principal g-values g|| = 2.0415 and g┴ = 2.0056 was identified as being an O2

-

centre while centre II with an isotropic g-factor 2.0096 was attributed to an F+-

centre (singly ionized oxygen vacancy). Centre III was also assigned to an F+-

centre with a small g-factor anisotropy (g|| = 1.974 and g┴ = 1.967). Additional

defect centres were observed during thermal annealing experiments and one of

them appearing around 330C grew with annealing temperature. This centre

(assigned to an F+-centre) seems to originate from an F-centre (oxygen vacancy

with two electrons) and the F-centre appeared to correlated= with the observed

thermally stimulated luminescence peak in Y2O3:Er phosphor. The trap depth for

this peak was determined to be 0.97eV from thermally stimulated luminescence

data.

NIR to Visible Up-Conversion, Infrared Luminescence, Thermoluminescence and

Defect Centres in Y2O3:Er Phosphor. V.Singh, V.K.Rai, I.Ledoux-Rak, S.Watanabe, T.K.G.Rao, J.F.D.Chubaci, L.Badie, F.Pelle, S.Ivanova: Journal of

Physics D, 2009, 42[6], 065104