LaOBr中Ce—Tb、Tm—Er间能量传递的光声光谱和光致发光研究

THE STUDY OF ENERGY TRANSFER BETWEEN Ce^(3+)-Tb^(3+)AND Er^(3+) -Tm^(3+) IN LaOBr BY PHOTOACOUSTIC AND PHOTOLUMINESCENT SPECTRA

本文首次报导了发光材料中两个不同稀土离子间能量传递的光声光谱研究。测量了LaOBr:Tb,Ce和LaOBr:Er,Tm体系的光声光谱,结合它们的光致发光特性,讨论了Ce^(3+)对Tb^(3+)的敏化、Tm^(3+)对Er^(3+)的猝灭。基质中掺入两种不同稀土离子后光声光谱的变化进一步证实了它们间的能量传递都伴随着多声子过程。分析LaOBr:Er,Tm的光声光谱,对Er^(3+)r的红光猝灭的机制提出了新的解释。

The photoacoustic spectral study of energy transfer between two rare earth ions in phosphor are first reported. Combined with photoluminescent spectra (PLS) and photoacoustic spectra (PAS) , the mechanism of sensitization of Ce3+ to Tb3+ and quenching of Tm3+ to Er3+ in LaOBr are discussed. In phosphor LaOBr : Tb, Ce,under 365nm excitation, the emissions of Tb3+are enhanced obviously by Ce3+, and the photoacoustic peak of Ce3+ increases. It suggests that the sensitization of Ce3+ to Tb3+ is phonon assisted energy transfer. In LaOBr : Er, Tm system, the visible emission (green: 4S3/2-4I15/2, red :4F9/2-4I15/2) of Er3+ are quenched by co-doped Tm3+. Among four main photoacoustic peaks of Er3+, the intensities of PA peaks at 527nm and 646nm which correspond to the absorption of energy levels 2Hn/2 and 4F9/2 of Er3+ respectively increase obviously with Tm3+ while other two (372nm and 486nm )keep constant. Our results not only confirm that the cross relaxation of Er3+: 4S3/2-4F9/2,11/2 and Tm3+:3H6-3H4,5 causes the quenching of visible emissions of Er3+, but also suggest that there exists another cross relaxation of Er3+: 4F9/2 - 4I13/2 and Tm3+:3H6- 3H5 which raises the quenching of red emission of Er3+.