Synthesis Of Rare-earth Doped NaYF₄ Luminescence Materials By Sol-gel Method And The Property Investigation

In this thesis,phase transformation process of Na YF₄ under different parameters was researched,rare earth doped?-Na YF₄ materials wereprepared.Theupconversionluminescence properties of the samples were studied.The maincontents and results of the research are as follows:1.The Na YF₄ phosphors were synthesized by sol-gel method at low temperature.The phase transformation process of the Na YF₄ samples which weresynthesized with different complexing agents?i.e.isopropanol,tartaric acid,ethylenediamine tetraacetic acid disodium salt and citric acid,respectively?was different with the variation of calcination temperature.2.Under the excitation of 980 nm laser diode,the samples of ?-Na YF₄:Yb³⁺,Tm³⁺phosphorsdisplayed bright upconversion luminescence?UCL?,which was generated from the energy level transition of Tm³⁺ ions.With the increase of Yb³⁺ doping concentration,the UCL intensity increased firstly and then decreased.While with the increase of the concentration of Tm³⁺,the UCL intensity of bluelight was decreased,and the intensity of greenlight and redlight upconversionwas inhibited firstly and then increased and finally decreased.The energy levels transition of ⁵S₂/⁵F_<sub>4?⁵I₈ and ⁵F₅?⁵I₈ of Ho³⁺ ions were observed in the system of ?-Na YF₄:Yb³⁺,Ho³⁺.The UCL intensity increased firstly and then decreased with the increase of Yb³⁺ and Ho³⁺ ions.In the Yb³⁺,Ho³⁺,Tm³⁺ doped ?-Na YF₄ materials,with the increase of Tm³⁺,Ho³⁺ and Yb³⁺ doping concentration,the UCL intensity of blue,green and red light emission of the samples varied.Calculation of the CIE color coordinate of the ?-Na YF₄:Yb³⁺,Ho³⁺,Tm³⁺ nanoparticles revealed that with the adjustment of Tm³⁺,Ho³⁺ and Yb³⁺ doping concentration and the excitation power of 980 nm LD,the multi-color UCL can be realized.Approximately single red light output with the CIE color coordinate of x=0.545,y=0.306 and white light output with the CIE color coordinate of x=0.325,y=0.320 can be obtained in the synthesized ?-Na YF₄: Yb³⁺,Ho³⁺,Tm³⁺ nanoparticles.3.The ¹D₂?³F_<sub>4,¹D₂?³H₅,1G4?³H₆,1G4?³F₄ and ³F₃?³H₆ energy level transition of Tm³⁺ and the 4G7/2?⁴I₉/2,4G9/2?⁴I₉/2,4G7/2?⁴I₁1/2 and 4S3/2,4F7/2?⁴I₉/2energy level transition of Nd³⁺ ions have been generated in the synthesized ?-Na YF₄:Nd³⁺,Tm³⁺,Yb³⁺,Mn²⁺ phosphors.It was found that with the increase of Nd³⁺doping concentration,the blue light was gradually weakened and the red,yellow and green light firstly enhanced and then weakened.With the increase of the doping concentration of Mn²⁺ ions,the UCL intensities in the blue light region increased firstly and then decreased.Meanwhile,the UCL intensities in the red,yellow and green light region gradually increased.Color-tunable UCL of the sample was generated by the continuous variation of the pumping power of 980 nm LD.4.The ³P₂?³H₄,³P₁?³H₄,³P₀?³H₄,³P₁?³H₅,³P₀?³H₅,³P₁?³H₆,³P₀?³H₆ and ³P₀?³F₂energy level transitions of Pr³⁺were generated in the synthesized Yb³⁺ and Pr³⁺ doped ?-Na YF₄ materials.The UCL intensity decreased with the increase of Yb³⁺ and Pr³⁺ concentration.After the incorporation of Mn²⁺ and Fe³⁺ into the system,the UCL relative luminous intensity of the samples changed.With the increase of Mn²⁺-doping concentration,the UCL intensity ratio of red to blue emission?IRed/IBlu?and red to green emission?IRed/IGreen?reached the maximum when the Mn²⁺doping concentration was at 40% and 20%,respectively,which was 12.8 times and 7.8 times as much as that of the sample with the Mn²⁺doping concentration of 1%.With the increase of Fe³⁺doping concentration,the UCL intensity ratio of red to blue emission?IRed/IBlu?and red to green emission?IRed/IGreen?reached its maximum when the Fe³⁺doping concentration was at 40%,which was 5.2 times and 7.5 times as much as that of the sample with the Fe³⁺ doping concentration of 1%.Color-tunable UCL of the sample was generated by adjustment of Mn²⁺ and Fe³⁺ doping concentration.