Increased downconversion efficiency and improved near infrared emission by different charge compensations in CaMoO_4:Yb^(3+) powders  

作　　者：曹雪琴 魏涛 陈永虎 尹民 郭常新 张慰萍 

机构地区：[1]Department of Physics,University of Science and Technology of China [2]School of Mechanical and Electrical Engineering,Hefei University of Technology

出　　处：《Journal of Rare Earths》2011年第11期1029-1035,共7页稀土学报（英文版）

基　　金：Project supported by the National Natural Science Foundation of China (10774140,11074245,11011120083);Knowledge Innovation Project of the Chinese Academy of Sciences (KJCX2-YW-M11);Special Foundation for Talents of Anhui Province,China (2007Z021)

摘　　要：All of the samples were synthesized by sol-gel methods.Two approaches to charge compensation,（i） 2Ca2＋→Yb3＋＋M＋,where M＋ is an alkali ion like Li＋,Na＋ and K＋,and（ii） indirect charge compensation：3Ca2＋→2Yb3＋＋vacancy,were studied in detail.It was found that charge compensation would be very beneficial for the growth of the grains,especially in Li＋ ions added samples.All the grains were homogeneously spherical with less boundaries;in addition,a great variety of the absorption ability in different charge compensation samples were observed：in comparison with the phosphors without charge compensation,indirectly charge compensated and Li＋ ions added phosphors showed much stronger absorption strength in the ultraviolet（UV） region whereas that of Na＋ and K＋ ions added samples was much weaker;moreover,measurements of the emission intensities showed that：in comparison with the phosphors without charge compensation,the visible emission intensity from MoO42-decreased a lot in indirectly charge compensated and Li＋ ions added phosphors,whereas there was a remarkable increase of the near infrared（NIR） emission intensity from Yb3＋ ions in the two types of samples under 266 nm excitation,implying more efficient energy transfer（ET） from MoO42-to Yb3＋ ions;at last,measurements and analysis of the decay curves of the visible 495 nm emission were carried out,and it was found that the energy transfer from MoO42-to Yb3＋ ions were more efficient in the two above types of phosphors.The theoretical quantum cutting（QC） efficiency was also improved greatly.Overall,the addition of Li＋ ions would be very beneficial for the morphology of the powders in addition to the growth of the grains.It was advantageous to increase the downconversion（DC） quantum efficiency;however,indirect charge compensation would enhance the NIR emission intensity to the most for its strongest absorption ability in the UV region.All of the samples were synthesized by sol-gel methods.Two approaches to charge compensation,（i） 2Ca2＋→Yb3＋＋M＋,where M＋ is an alkali ion like Li＋,Na＋ and K＋,and（ii） indirect charge compensation：3Ca2＋→2Yb3＋＋vacancy,were studied in detail.It was found that charge compensation would be very beneficial for the growth of the grains,especially in Li＋ ions added samples.All the grains were homogeneously spherical with less boundaries;in addition,a great variety of the absorption ability in different charge compensation samples were observed：in comparison with the phosphors without charge compensation,indirectly charge compensated and Li＋ ions added phosphors showed much stronger absorption strength in the ultraviolet（UV） region whereas that of Na＋ and K＋ ions added samples was much weaker;moreover,measurements of the emission intensities showed that：in comparison with the phosphors without charge compensation,the visible emission intensity from MoO42-decreased a lot in indirectly charge compensated and Li＋ ions added phosphors,whereas there was a remarkable increase of the near infrared（NIR） emission intensity from Yb3＋ ions in the two types of samples under 266 nm excitation,implying more efficient energy transfer（ET） from MoO42-to Yb3＋ ions;at last,measurements and analysis of the decay curves of the visible 495 nm emission were carried out,and it was found that the energy transfer from MoO42-to Yb3＋ ions were more efficient in the two above types of phosphors.The theoretical quantum cutting（QC） efficiency was also improved greatly.Overall,the addition of Li＋ ions would be very beneficial for the morphology of the powders in addition to the growth of the grains.It was advantageous to increase the downconversion（DC） quantum efficiency;however,indirect charge compensation would enhance the NIR emission intensity to the most for its strongest absorption ability in the UV region.

关 键 词：DOWNCONVERSION MOLYBDATES charge transfer Yb3＋ rare earths 

分 类 号：TB44[一般工业技术]