铕(Ⅲ)激活铌酸钇的发光

Photoluminescence of YNbO_4:Eu^(3+)

在使用Li_2So_4作助熔剂的条件下,由相应的氧化物高温合成了Y_(1-x)Eu_xNbO_4(0≤x≤0.30),研究了各试样的光致发光。254nm紫外光激发下的发射光谱包括两个部分:位于330～480nm的弱发射谱带,相当于NbO_4基团的电荷转移态跃迁发射;在535～720nm之间有5组锐线状发射光谱,分别归属于Eu^(3+)的~5D_1—~7F_j(j=1,2,3)和~5D_o—~7F_j(j=1,2,3,4)跃迁发射,其中主发射峰是位于612.7nm的~5D_o—~7F_2跃迁发射。~5D_o—~7F_2发射的激发光谱包括NbO_4基团电荷转移态的强激发带,和一些Eu^(3+)f—f跃迁弱激发锐线谱。随着Eu^(3+)浓度的增大,两种激发都逐渐增强,这表明光致发光过程中存在着能量由NbO_4→Eu^(3+)的传递。当Eu^(3+)浓度大于0.15mol时发生发光的浓度猝灭。

Polycrystalline undoped and Eu^(3+)-doped YNbP_4 were synthesized by solid state reaction with the aid of flu- x.The flux used was Li_2SO_4 and amount- ed to 30wt% of starting materials 99.99% pure Y_2O_3,Eu_2O_3 and Nb_2O_3 in stoichiometric quantities.Photoluminese- ence of YNbO_4:Eu^3+was studied.Its emi- ssion spectrum excited by 254nm UV light consists of two parts,a weak band ranging 330～480nm corresponding to the charge transfer(CT)emission of niobate group,and a series of strong sharp line emi- ssions of Eu^(3+5)D_1—~7F_1 and ~5D_O—~7F_j tran- sitions.The main emission peak at 612.7nm originates from Eu^(3+5)D_O—~7F_2 transition, that indicates that Eu^(3+) ions were loca- ted on unsymmetric lattice sites.The ex- citation spectrum of Eu^(3+5)D_O—~7F_2 transi- tion emission includes a strong band of CT transition of NbO_4 group and many weak line of Eu^(3+)f—f transition.That ex- plains that there happens energy transfer from NbO_4 to Eu^(3+).This has been further proved by the concentration effect of Eu^(3+) ions on the CT excitation spectrwn of NbO_4.This effect shows that the higher Eu^(3+) concentration is doped within 0≤ x≤0.15 in the system of Y_(1-x)Eu_xNbO_4, the weaker the excitation and emission spectra of CT transitions of NbO_4 group are.