Study On Optical Temperature Sensing Properties Of Eu³⁺,Tb³⁺ Co-activated Phosphors

With the development of technology,the optical temperature measurement technology based on rare earth ions has been widely concerned because of its characteristics of non-contact temperature measurement,environmental protection and high sensitivity.In order to obtain excellent luminescence characteristics and temperature sensing performance,the selection of the appropriate rare earth ion materials is also very critical.Eu³⁺,Tb³⁺co-doped materials have the advantage not only because they are dual luminescent centers,which are excited by fluorescence and are not affected by the excitation photothermal effect,but also Eu³⁺and Tb³⁺have strong red emission and green emission,respectively.In the same host material,if Eu³⁺and Tb³⁺have different trends of luminescence thermal quenching,then the fluorescence intensity ratio?FIR?of both will change with the temperature,and cause the luminescence color of the material to change,so the relative sensitivity may be significantly improved.Therefore,this paper will explore in detail the temperature sensing performance of Eu³⁺and Tb³⁺co-doped different host materials.In this paper,urea is used as precipitant and homogeneous precipitation method is adopted.Y₂O₃:Eu³⁺,Tb³⁺nanophosphors of different particle sizes were prepared by changing the molar ratio of urea to rare earth ions(urea/Re³⁺=10,20,30,60,100,200).The crystal structure and morphology of the sample were characterized by XRD and FE-SEM.The results of XRD test show that the sample we prepared is a body-centered cubic structure.The observation of FE-SEM showed that the particle size of the sample decreased with the increase of urea/Re³⁺value.The temperature sensing characteristics of all samples were studied in the temperature range of 313 K-513 K.The luminescence intensity of Eu³⁺and Tb³⁺decreased with increasing temperature in Y₂O₃ host material.However,the thermal quenching trend of Tb³⁺is slower than that of Eu³⁺,so the FIR values of Tb³⁺and Eu³⁺will increase with the increase of temperature,which can be used to characterize the temperature.In addition,when temperature is characterized by FIR,the sensitivity of temperature sensing of samples increases with the decrease of particle size due to the surface defect effect.Due to the influence of size limitation,the relative sensitivity decreases with the decrease of particle size.In addition,as the temperature increases,the luminescence color of the sample can continuously change from orange to green,so the color change can also represent the temperature.In addition,sodium citrate is used as chelating agent and hydrothermal method is adopted,NaLa?MoO₄?₂:Eu³⁺,Tb³⁺phosphors with different morphologies were synthesized by changing the molar ratio of sodium citrate to rare earth ions(Cit^3-/Re³⁺=0,0.5,1,1.5,2),the crystal structure and morphology of the sample were characterized.The XRD test results show that,except for the samples of Cit^3-/Re³⁺=0and 2,there is no heterophase in the samples we prepared,and are body-centered tetragonal scheelite structure.FE-SEM shows that the morphology of each sample varies with the change of Cit^3-/Re³⁺.The luminescence and temperature sensing properties of NaLa?MoO₄?₂:Eu³⁺,Tb³⁺(Cit^3-/Re³⁺=0.5,1,1.5)phosphors were studied in the temperature range of 293 K-593 K.Due to the difference of thermal quenching behavior between Eu³⁺and Tb³⁺in NaLa?MoO₄?₂ host material,the FIR changes with the change of temperature,which can be used to characterize the temperature.The temperature sensing sensitivity of the sample increased with the increase of Cit^3-/Re³⁺.When the temperature is 560 K,the relative sensitivity of the three samples reaches 1%K^-1.In addition,the luminescence color of the samples gradually changed from yellow-green to orange-red with the increase of temperature,and it was found that the color change is more obvious for samples with high Cit^3-/Re³⁺values.The above results show that in Eu3+and Tb3+co-doped optical temperature sensing materials,particle size and morphology of the materials have significant effects on the optical temperature sensing properties.The research results of this paper will have important guidance and reference significance for the design and preparation of rare earth ion activated optical temperature sensing materials.