Preparation And Luminescence Properties Of Tungstate Materials

In recent years,rare earth ions doped up-conversion luminescent?UCL?materials have become a hot spot of current research.Tungstates are excellent UCL materials,because they have table chemical properties,so that they have irreplaceable advantage in many applications.Tungstates have been widly used in various fields as an excellent up-conversion luminescent materials.In this thesis,this paper use rare earth ions doped tungstates as research object,the major works are shown as follows:1.Er³⁺ single-doped and Er³⁺,Yb³⁺ co-doped NaY?WO₄?₂ phosphors were synthesized by solid-state reaction method.The samples were characterized by XRD and emission spectral analysis,NaY?WO₄?₂:Yb³⁺,Er³⁺ exhibits excellent bright green emission under 980 nm excitation.The red emission of the phosphor was not changed by increasing Yb³⁺ ion concentrations,and the material exhibited excellent color purity and color stability,and the green emission is strong.When excited by the 1550 nm laser,the samples still show green emission,the fraction of red emission slightly increased compared with that observed under 980 nm excitation.2.Er³⁺,Tm³⁺ co-doped NaY?WO₄?₂ phosphors were synthesized by solid-state reaction method.The samples were characterized by XRD and emission spectral analysis.The sample shows strong green emission when excited by 980 nm LD,and the ratio of the red and green emission shows decreases with increasing the excitation power.The emission color changes from white to the green region directly,and the range is large relatively.The samples show red emission when excited by 1550 nm LD,the ratio of the red and green emission shows increase firstly and then decrease with increasing the excitation power.3.Er³⁺,Yb³⁺ co-doped NaLa?WO₄?₂ were synthesized by solvothermal reaction method.The luminescence properties of the sample were studied by changing pH,the ratio of ethylene glycol to water,temperature,and the amount of complexing agent.Besides,samples are synthesized successfully at low temperature 120 ?,its morphology are regular.The samples are further dispersed with the doping of PVP,the best degree of dispension can be obtained while the PVP is 0.3 g.The samples show regular structure and small particles when the ratio of ethylene glycol to water is 4:1.The maximum emission intensity of the phosphors are achieved at pH is 10.The maximum emission intensity of the sample is achieved at 2 mol%Er³⁺ and 8 mol%Yb³⁺under 980 nm LD excitation,whereas the intensity of the sample with the optimum doping concentration of 8 mol% Er³⁺ and 16 mol%Yb³⁺ is relative weak at 1550 nm excitation.