Published online by Cambridge University Press: 21 March 2011
This paper presents for the first time a comparison between the luminescence properties (viz. emission and excitation spectra, lifetimes, and concentration quenching) of nanocrystalline and microcrystalline Lu2O3:xTm3+ (x= 0.1– 5 mol%). The results show that the most important difference between the two size regimes is the higher defect concentration in the nanoparticles. These defects give rise to a broadband emission (λmax = 430 nm), and to partial quenching of the Tm3+ emission, in addition to the expected concentration quenching by cross-relaxation between Tm3+ ions. The defect concentration seems to be similar in all nanocrystalline samples, so that those with the lowest Tm3+ concentrations experience the most pronounced quenching. The nature of these defects is as yet unknown. The local structure around the Tm3+ ions is not noticeably different in the two size regimes. No evidence of phonon confinement or quantum size effects was observed in the Tm3+luminescence.