Study On Optical Temperature Sensing Properties Of Pr³⁺ Doped And Pr³⁺,Tb³⁺ Co-doped NaY(MoO₄)₂ Phosphor

Temperature is a basic parameter of scientific research,and the accurate measurement of temperature is very important in industrial production,national defense construction,bio-medical treatment and other fields.In the non-contact temperature measurement technology,fluorescence intensity ratio temperature measurement technology is a promising temperature measurement method.The fluorescence intensity ratio between thermally coupled energy levels of rare earth ions is used in common temperature sensing materials.However,the distance between thermally coupled energy levels is close and the energy difference is small,and the relative sensitivity of thermally coupled energy level type temperature sensing materials is determined by the energy level spacing of thermally coupled energy levels.So,the relative sensitivity of the material is difficult to improve further.In this paper,we prepare Pr³⁺doped and Pr³⁺,Tb³⁺co-doped NaY(Mo O₄)₂ phosphors and improve the temperature measuring performance of temperature sensing materials by using the fluorescence intensity ratio technology of non-thermal coupled energy levels.The main contents of this paper are as follows:(1)Pr³⁺doped NaY(Mo O₄)₂ phosphor was prepared by hydrothermal method,and samples of different sizes were prepared by changing the dosage of sodium citrate(Cit^3-/Re³⁺=0,0.5,1,2).X-ray diffraction(XRD)and field emission scanning electron microscopy(FE-SEM)were used to characterize the internal structure and morphology of phosphors.In addition,the relationship between luminescence intensity and temperature was studied by temperature-dependent emission spectrum.From the XRD pattern,it is found that the sample prepared by the experiment is tetragonal scheelite structure.With the increase of sodium citrate,the sample does not appear any impurity peaks,and the prepared samples are all pure phase.FE-SEM results indicated that the size of sample increased with the ratio of sodium citrate to rare earth.According to the temperature dependent spectra of the samples,Pr³⁺has luminescence of different energy levels(¹D₂-³H₄,³P₀-³H₄ and ³P₀-³F₂)in the range of visible light.And the quenching trends of different energy levels are obviously different,so the two groups of FIR based on non-thermally coupled energy levels can be realized.In the actual measurement process,the two groups of FIR can verify each other,which ensures the accuracy of temperature measurement of temperature sensing material.In addition,the maximum relative sensitivity of the samples reached 1.00%K^-1 at 313K,and the relative sensitivity of the samples can still maintain near the maximum in the human temperature(308-315K).(2)Sodium citrate was used as chelating agent to synthesize Pr³⁺,Tb³⁺co-doped NaY(Mo O₄)₂ phosphors(Cit^3-/Re³⁺=0,0.5,1,1.5,2)with hydrothermal method.The test results show that the structure of phosphors is body-centered tetragonal structure,and adding sodium citrate can change the morphology of the sample.In addition,it was demonstrated that the luminescence intensity of Pr³⁺and Tb³⁺decreased with temperature.As the temperature increases,the luminescence intensity of Pr³⁺and Tb³⁺differs significantly,so the fluorescence intensity ratio of Pr³⁺and Tb³⁺will increase with the increase of temperature,which can be used to represent the temperature.When Cit^3-/Re³⁺=2 and the temperature is 384K,the relative sensitivity of the sample is3.00%K^-1,which is higher than that of the previously reported co-doped molybdate material.In addition,the luminescence color of the sample will continuously vary from green to red with the increase of temperature,the change of temperature can be represented more intuitively by the change of color.The research of this paper shows that NaY(Mo O₄)₂:Pr³⁺and NaY(Mo O₄)₂:Pr³⁺,Tb³⁺phosphors are excellent temperature measuring materials,and with the increase of chelating agent dosage,not only change the morphology of phosphors,but also improve the optical temperature measuring performance of materials.The results of this paper provide a new direction for the design and performance improvement of phosphors.