Red And Near-infrared Up-conversion Emission Of Rare-earth Doped Oxyfluoride And Fluoride Systems

The up-conversion（UC）luminescence materials has attracted a great deal ofattention of the researchers from all over the world because it has a good appliedprospectin three-dimensional display, anti-counterfeiting technology, biologicalfluorescence probe and solar battery, etc. However the existing problems is that theintensity of red UC emission which is one of the three primary colors, is far less thanthe green and blue in the visible light region; on the other hand, in the near-infraredlight area, the presence of visible light will affect the use of the material in thenear-infrared up-conversion luminescence materials. Therefore, searching for intenseand pure red UC and near-infrared UC phosphors have important actual significance.In order to search for intense and pure red UC and near-infrared UC phosphors, themain works are described in brief as follows:1. Er3+doped NaYbF4powders were synthesized by coprecipitation method.TheUC luminescence properties of under980nm excitation are investigated，it is foundthat bright and pure red UC emission is obtained. The dependences of the intensitiesfor red and green emissions on Er3+concentration are explored. On this basis, Sc3+ions were doped to enhance the intensity of the red UC emission, it is found that theintegral intensity of the red emission has been enhanced1.7times than un-doped ones,its reinforcement mechanism was also analyzed. This is because the introduction ofSc3+ions has changed the symmetry of the substrate.2. Yb3+and Er3+co-doped Y5O4F7powders were synthesized by a hightemperature fluorination-reaction method. The influence of NH4HF2content on thestructure and the UC emission intensity of the samples were studied. It is found thatthe intensity of the impurity peak is weakest than others samples when the molar ratioof NH4HF2to RE is1, and the intensity of UC emission is also strongest. It is foundthat bright and pure red UC emission was observed under980nm laser excitation. Onthis basis we continue to dope the Li+/Na+ions to increase the intensity UC intensity, it is found that the integral intensity of the red emission have been enhanced3and2.3times, respectively. Spectral probing method with Eu3+and FT-IR are used to discussthe reason to improve the emission intensity，it’s found that The introduction of Li+and Na+ions not only lowers the local symmetry of rare earth ions, but also reducesthe quantity of high-energy vibration groups absorbed in the powder, resulting in theenhancement of the red UC emission.3. Tm3+or Nd3+doped YbF3/YbOF powders were synthesized by a hightemperature fluorination-reaction method. The UC luminescence properties of under980nm excitation are investigated, it is found that highly pure near-infrared UCemission is obtained. The dependences of the purity for near-infrared UC emission onTm3+or Nd3+concentration were explored. The possible mechanism of UCluminescence was also discussed.