Up-conversion Luminescence Of Nd³⁺/Yb³⁺/Tm³⁺(Er³⁺) Tri-doped Oxide Systems Under 808nm Excitation

Up-conversion is a particular luminescence phenomenon that can absorb low energy photons and emit high energy photons.It can be used in multiple fields such as infrared sensor,three-dimensional display,optical storage,medical diagnostics and laser anti-counterfeit.Due to its unique advantages in anti-counterfeit,such as strong concealment,good stability,simple use and low cost,researches in the up-converted luminous material has been widely brought up.However,common up-converted anti-counterfeit products can only be used in 980 nm,with limited emission colors.-Based on the situation mentioned above,some work are investigated and described as follows:(1)Tm3+/Nd3+/Yb3+tri-doped CaTeO3 phosphors were prepared using a high temperature solid-state reaction method.The sample shows high pure blue luminescence under 808 nm excitation since only single emission band peaks at 476 nm.The best doping concentrations of Nd3+and Yb3+are 0.007 and 0.01 respectively according to the study of its emission intensity.Process of energy transfer for Nd3+→Tm3+and Nd3+→Yb3+→Tm3+has been discussed based on the dependence between the intensity of up-conversion emission and excitation power along with the near infrared luminescence spectra.The Yb3+ion acts as a bridge during the energy transfer between Nd3+and Tm3+which made the process more efficiently.The luminescence lifetime of Nd3+ions has been measured under different doping conditions and the efficiency of their energy transfer is obtained.(2)By using high temperature solid-state reaction method,Er3+/Nd3+/Yb3+co-doped NaY(MoO4)2 compounds were prepared.Strong green up-conversion luminescence(at 535 nm and 558 nm)and weak red up-conversion fluorescence(at 669 nm)has been observed under 808 nm excitation.The ratio of IG/IR(about 40)is hardly dependent on the concentrations of Yb3+,indicates that Er3+/Nd3+/Yb3+co-doped NaY(MoO4)2 can easily realize high pure green up-conversion luminescence under 808 nm excitation.The low probability of the energy transfer and non-radiative transition corresponds to the 4F9/2 level of Er3+is responsible for the high pure green up-conversion emission.The luminescence intensity of Er3+decreases after the introduction of Nd3+or Yb3+.Only when Nd3+and Yb3+are introduced at the same time,the luminescence intensity of Er3+ is increased by 12 times.It is shown that this up-conversion performance is depend on the competition between Nd3+→+Yb3+→Er3+and Er3+→Nd3+/Yb3+energy transfer processes under 808 nm excitation.