Li^+增强Ho^(3+)/Yb^(3+):Y_2O_3纳米晶的上转化发光研究

采用凝胶溶胶法制备了不同浓度的Y2O3:Ho3+/Yb3+/Li+纳米晶,并且系统研究了不同掺杂浓度对上转化荧光现象的影响。首先,通过XRD图形判断了晶体结构的生成,再通过980 nm的激光器和荧光光谱仪测得的光谱图,发现了位于520~579 nm的绿光、635~674 nm的红光等两条很强的可见光,还有一条较弱的位于743~775 nm的近红外发光。最后,通过与能级图比较和分析可以得出:它们分别是5F4/5S2→5I8,5F5→5I8和5F4/5S2→5I7荧光跃迁。可以看出:在掺杂入Li+之后,上转化荧光得到了极大增强。

Li^+,Bi^3+掺杂对Lu2O3∶Ho^3+,Yb^3+粉体发光性质的影响

采用高温固相法制备了Li^+、Bi^3+掺杂Lu2O3∶Ho^3+,Yb^3+粉体。用X射线衍射仪分析了合成粉体的微结构,用场发射扫描电子显微镜观测了样品的形貌及尺寸,用紫外可见近红外荧光光谱仪分析了合成粉体的上转换发射光谱以及能级寿命。结果表明:Li^+、Bi^3+掺杂的Lu2O3∶Ho^3+,Yb^3+粉体,仍然保持Lu2O3立方相结构。Li^+或Bi^3+掺杂后,合成粉体的分散性更好,颗粒更均匀,且更加接近球形,Li^+掺杂后粉体颗粒尺寸明显增加。用980 nm激发,4%Li^+或1.5%Bi^3+掺杂后,合成粉体中Ho^3+的绿光光强分别提高了约3.9倍、2.8倍。随着Li^+浓度的增加,合成粉体中Ho^3+的5S2能级寿命先增加后减小;随着Bi^3+浓度的增加,合成粉体中Ho^3+的5S2能级寿命逐渐减小。

Ho^(3+)/Yb^(3+)共掺ZnO-Al_2O_3-GeO_2-SiO_2玻璃陶瓷的制备和上转换发光性质

综合ZnO-Al_2O_3-SiO_2系和锗酸盐玻璃陶瓷的优点,采用熔融-晶化法首次制备了Ho^(3+)/Yb^(3+)共掺以ZnAl_2O_4为主晶相的ZnO-Al_2O_3-GeO_2-SiO_2系玻璃陶瓷。因[GeO_4]四面体和[SiO_4]四面体都是玻璃网络形成体,讨论了GeO_2取代SiO_2对玻璃陶瓷样品硬度及发光性能的影响,最终确定GeO_2的取代量为10.55%(w/w)时,玻璃陶瓷综合性能最佳。在980 nm泵浦光的激发下,发现强的绿色(546 nm)和弱的红色(650 nm)上转换发光,并研究了不同Ho^(3+)/Yb^(3+)掺杂比对样品上转换发光的影响,最终结果表明当Ho^(3+)/Yb^(3+)掺杂比为1∶11(n/n)时样品荧光强度最强,在绿色上转换发光材料方面具有潜在的应用。

Tm3+/Ho3+/Yb3+掺杂Ga2O3-GeO2-Li2O玻璃的上转换发光性能研究

采用熔融淬冷法制备了Tm^3＋/Ho^3＋/Yb^3＋掺杂的Ga2O3-GeO2-Li2O玻璃。测试了样品的拉曼光谱、吸收光谱、980 nm和808 nm泵浦下的上转换发射光谱。详细调查了在980 nm和808 nm激发下不同的Yb2O3掺杂含量对Tm^3＋/Ho^3＋掺杂的镓锗锂玻璃的上转换发射光谱的影响,分析了稀土离子间的能量传递。研究发现：980 nm泵浦下样品观察到明显的545 nm和657 nm发射和微弱的476 nm发射峰。随着Yb^3＋浓度的增大,由于Yb^3＋对Tm^3＋和Ho^3＋的有效的能量传递增强了红光和绿光发射强度,红光的增长率是快于绿光的,Yb2O3的掺杂量为0.7 mol%时I657/I545强度比率达到最高。808 nm激发下可以观察到弱的476 nm的蓝光和545 nm的绿光及强烈693 nm发射。

Preparation and upconversion luminescence of monodisperse Gd_2O_3:Ho^(3+),Yb^(3+)nanocrystals

Gd2O3：Ho^3＋,Yb^3＋ nanocrystals were synthesized via solvothermal method. X-ray diffraction （XRD）, transmission electron microscopy （TEM）, absorption and upconversion spectra were employed to characterize the synthesized nanocrystals. The results of XRD and TEM showed that obtained Gd2O3：Ho^3＋,Yb^3＋ nanocrystals were cubic in crystal structure and uniform spherical in morphology. The average crystallite size was calculated to be 7.5 nm. Green and red up-conversion emissions corresponding to （^5F4, ^5S2）→^5I8 and ^5F5→^5I8 transition were observed upon 980 nm excitation at room temperature. The results indicated that both green and red luminescence were based on the two-photon processes. Laser power and doping concentration dependence of the up- converted emissions were studied to understand the upconversion mechanisms. Excited state absorption and energy-transfer processes were discussed as the possible mechanisms for the visible emissions.

Spectroscopic properties and energy transfer of Nd^(3+)/Ho^(3+)-doped Ga_2O_3-GeO_2 glass by codoping Yb^(3+) ion

This study presented the luminescence properties of Nd^3＋/Yb^3＋/Ho^3＋ dopant ions inside a host based on Ga_2O_3-GeO_2-Li_2O（GGL） glass. The measured differential scanning calorimetry result showed that GGL glass exhibited excellent stability against devitrification with ？T=135 oC. Obvious 543 and 657 nm emissions were observed in Nd^3＋/Ho^3＋-codoped sample. The incorporation of Yb^3＋ into Nd^3＋/Ho^3＋-codoped glass system had resulted in enhanced upconversion emission intensity under the excitation of 808 nm and/or 980 nm laser diode（LD）. The possible mechanisms and related discussions on this phenomenon were presented. It was noted that the presence of Yb^3＋ yielded an enhancement about 7 and 11 times in the 543 and 657 nm emission intensities respectively under 808 nm excitation due to the energy transfer from Nd^3＋ to Ho^3＋ via Yb^3＋ ion. Here Yb^3＋ played a major role as a bridging ion. While enhanced 543 and 657 nm emission intensities under the excitation of 980 nm LD originated from the sensitization effect of Yb^3＋. Our results showed that Nd^3＋/Ho^3＋/Yb^3＋ triply doped GGL glass might be a promising candidate for the development of visible-laser materials.