共沉淀法制备Y_2SiO_5∶Er^(3+),Yb^(3+),Tm^(3+)及其上转换发光性能研究

Upconversion luminescence properties of Y_2SiO_5 : Er^(3+),Yb^(3+),Tm^(3+) synthesized by co-precipitation method

采用化学共沉淀法制备了系列Y1.98-2xYb2xEr0.02SiO5(0.00≤x≤0.15)以及Y1.736Yb0.24Er0.02Tm0.004SiO5上转换发光材料,比较了室温下Y1.98-2xYb2xEr0.02SiO5(x=0.00,0.08)样品在400—1600nm范围内的吸收光谱,测量了所有样品在976nmOPO激光器激发下的上转换发射光谱,以及Er3+离子4S3/2(4F9/2)→4I15/2,Tm3+离子1G4→3H6荧光衰减曲线和不同激发功率下的上转换蓝光发射强度,从而分析讨论了Er3+,Tm3+在Y2SiO5中的上转换发光机理.研究结果表明:在1250℃相对较低的温度下合成了X2型单斜晶系Y2SiO5∶Ln3+(Ln3+=Er3+,Yb3+,Tm3+),Yb3+的敏化显著增强了样品在976nm附近的吸收能力,并大幅度加宽了该处的吸收带.分析上转换发射光谱发现:上转换绿光和红光强度都随着Yb3+浓度的增加先增强后减弱,但红光的猝灭浓度较高,归因于Er3+→Yb3+反向能量传递ETU4和Yb3+→Er3+正向能量传递ETU3过程的发生;上转换蓝光发射是三光子吸收过程,是通过Yb3+,Tm3+之间三次声子辅助的能量转移方式实现的.

A series of up-conversion luminescence materials of Y1. 98-2x Yb2x Er0. 02 SiO5 （0. 00≤x≤0. 15） and Y1. 736 Yb0. 24 Er0. 02 Tm0. 004SiO5 were synthesized by co-precipitation method. The absorption spectra from 400 to 1600 nm of Y1. 98-2xYb2xEr0. 02 SiO5 （ x = 0. 00,0. 08） were compared,and the up-conversion emission spectra of all samples were investigated when excited by 976 nm opo laser. The decay curves of Er3 ＋4 S3/2 （4F9/2 ） → 4I15/2,Tm3 ＋1 G4 →3H6,as well as the relationship between the blue up-conversion emission intensity and pumping power were measured,consequently,the possible up-conversion luminescence mechanisms of Er3 ＋ ,Tm3 ＋ in Y2SiO5 were discussed. The results show that X2-type monoclinic Ln3 ＋ （Ln3 ＋ = Er3 ＋ ,Yb3 ＋ ,Tm3 ＋ ） co-doped Y2SiO5 phosphors have been synthesised under relatively low temperature of 1250 ℃ ,and the absorption intensity and bandwidth are remarkably increased by Yb3 ＋ sensitizing around 976 nm. Up-conversion emission spectra has been analyzed and the results suggest that both the green and red lights increase first and then decrease with the increase of the Yb3 ＋ doping concentration. However,the concentration quenching of the red light emission is higher,due to the forward （ETU3） and back （ ETU4） energy transfer between Yb3 ＋ and Er3 ＋ ions; the blue emission occurs mainly through phonon-assisted energy transfer between Yb3 ＋ and Tm3 ＋ ions,which is a three photon absorption process.