Ce3+在Ln2SO6中的发光(Ln=La,Gd或Y)

Ce3+在La2SO6中的发光光谱和激发光谱与在Gd2SO6和Y2SO6中的比较有显著差别。从被Ce3+敏化的中心的激发光谱上观察到在La基质中于300和330nm附近还有二个激发峰,显示出在这三个基质中Ce3+有很接近的激发态情况,从漫反射光谱也得到证实。不过在La2SO6中Ce3+的发光起源于次最低的而不是最低的5d能级。

THE LUMINESCENCE OF Ce3+IN Ln2SO6(Ln=La,Gd OR Y)

La2SO6(LS), Gd2SO6 (GS) and Y2SO6 (YS) were prepared by a flux method in a reducing atmosphere. They are of the same type of structure, orthorhombic,with the space group I222, and the site Symmetry of Ln is C2.The luminescence of Ce3+ in them was studied v/ith their excitation spectra and emission spectra.The spectra of GS:Ce3+ and YS:Ce3+ are quite similar as expected, whereas those of LS:Ce3+ show marked differences.The excitation spectra of the samples prepared by codoping Ce3+ and another emission center which can be sensitized by Ce3+ e.g. Dy3+ in these three hosts monitored at Dy3+ emission line, show very similar behavior (Fig.2).The excitation peaks due to Ce3+ in GS:Ce3+, Dy3+ and YS:Ce3+, Dy3+ coincide with those of GS:Ce3+ and YS:Ce3+ in Fig.1, whereas the peaks located at-300nm and-330nm in LS:Ce3+,Dy3+ have no correspondence in LS:Ce3+. But it was argued that these two peaks also originated from Ce3+ and this was affirmed by diffused reflection spectrum of LS:Ce3+ (Fig.3).Hence the luminescence of Ce3+ in LS might be described as following:the 5d manifold of Ce3+ are split into 5 levels, in conformity with C2 site symmetry, three of them are obtained directly from the excitation spectra of LS:Ce3+, the other two are obtained from the excitation spectra of a center sensitized by Ce3+ or from the deffused reflection spectra and the emission is originated from the next lowest 5d state.Here it can be argued that two factors pertaining to the appearance of the uncommon emission from the next lowest 5d state are as follows. (1) small Stokes’ shift, and (2) narrower excitation peaks.