Study On Optical Temperature Sensing Properties Of NaLa?MoO₄?₂:SM³⁺,tb³⁺phosphor

In recent years,rare earth luminescent materials have played an important role in the fields of fluorescent anti-counterfeiting,display lighting and temperature sensing.With the development of modern industrial technology and science and technology,the requirements of temperature control or detection in various fields are becoming higher and higher.Because of its advantages of non-contact,high sensitivity,high accuracy and so on,optical temperature sensing technology is suitable for application in high pressure,high temperature,airtight,highly toxic and other extreme environments,which has attracted extensive attention of scientific researchers.Fluorescence intensity ratio?FIR?temperature measurement method has the advantages of non-contact,high temperature resistance,wide temperature range,fast response,measurable small object,etc.,so it is widely used in optical temperature sensing technology.In this paper,sodium citrate?Na₃C₆H₅O₇-Na₃Cit?was used as chelating agent to synthesize Sm³⁺,Tb³⁺co-doped Na La?MoO₄?₂ phosphors by hydrothermal method.The microstructure and crystal structure of the samples were characterized by X-ray diffraction?XRD?and field emission scanning electron microscopy?FE-SEM?.The results of XRD showed that the samples prepared by us had no impurity peak and were of tetragonal scheelite structure.It is found that the change of the content of sodium citrate has a great influence on the morphology of the sample by observing the spectrum of FE-SEM.In Chapter 3,the reason of the influence of the content of sodium citrate on the morphology of the sample is analyzed.However,the doping concentration of Sm3+has little effect on the morphology of the samples.The optical temperature sensing characteristics of Na La?MoO₄?₂:0.3%Sm³⁺,5%Tb³⁺(Cit^3-/Re³⁺=0,1,2)samples were studied in the temperature range of 303K-603 K.It was found that the luminescent intensity of Sm³⁺and Tb³⁺decreased with the increase of temperature in Na La?MoO₄?₂ matrix.However,the thermal quenching trend of Sm³⁺is relatively slow,belonging to the"weak coupling"type.The thermal quenching trend of Tb³⁺is relatively obvious,belonging to the"strong coupling"type.With the increase of temperature,the fluorescence intensity ratio?FIR?of Sm³⁺and Tb³⁺will increase,so it can be used to characterize the temperature.In addition,the temperature sensing sensitivity of the samples increased significantly with the increase of Cit^3-/Re³⁺.When Cit^3-/Re³⁺=2,the sensitivity of the sample reaches the maximum value of 0.0119 K^-1 at 603K.The relative sensitivity of the sample is the highest when Cit^3-/Re³⁺=0,and the maximum of the relative sensitivity is 1.93%K^-1 at 498K.In addition,the luminescent color of NaLa?MoO₄?₂:0.3%Sm³⁺,5%Tb³⁺(Cit^3-/Re³⁺=0,1,2)phosphors changed obviously with temperature.In the temperature range of 303K-603 K,the continuous change from yellow green to orange red can be realized,so the reaction temperature can be intuitionistic through the luminous color.We also studied the temperature sensing properties of NaLa?MoO₄?₂:x%Sm³⁺,5%Tb³⁺?x=0.1,0.3,1,1.5?phosphors with Cit^3-/Re³⁺=1 in the temperature range of 303K-603 K.The experimental results show that the sensitivity of the sample increases with the increase of Sm³⁺doping concentration.When the doping concentration of Sm³⁺is 1.5%,the sensitivity of the sample reaches the maximum value of 0.2521 K^-1 at 603K.The relative sensitivity of the samples increased with the increase of Sm³⁺concentration in the temperature range of 303 K-410 K,and decreased with the increase of Sm³⁺concentration in the temperature range of 460 K-603 K.When the Sm³⁺concentration is 0.1%,the relative sensitivity of the sample reaches the maximum value of 1.90%K^-1at 506K.In addition,the luminescent color of Nala NaLa?MoO₄?₂:x%Sm³⁺,5%Tb³⁺?x=0.1,0.3,1,1.5?phosphors also changes with temperature.A continuous change from green to orange red is achieved in the temperature range 303 K to 603 K.NaLa?MoO₄?₂:Sm³⁺,Tb³⁺phosphor is an excellent optical temperature sensing material with high sensitivity and relative sensitivity.And its luminescent color has obvious change with the temperature,which can directly reflect the change of temperature.