The Temperature Detection Technology Based On Thermal Quenching And Thermal Coupling Energy Levels

Because the temperature has a great influence on the luminescent properties of luminescent materials,some optical properties have a dependence on the temperature.Based on this phenomenon,fluorescence thermometry has been realized.In this paper,we mainly studied this influence from two aspects,and discussed the corresponding temperature detection technology.Firstly,when the temperature rises,the non-radiation transition will enhance,resulting in the decrease of the intensity and lifetime of the luminescence of luminescent material,which is known as thermal quenching.On the other hand,because the thermal coupling energy levels consistently meet the Boltzmann distribution during the glowing process,the fluorescence intensity ratio?FIR?of these two levels is dependent on the temperature.In this paper we have studied three method for temperature detection based on the effect of thermal quenching and?or?thermal coupling energy levels on the luminescence performance of fluorescent luminescent material:firstly,temperature detection for LED light based on the change of chromaticity coordinate caused by thermal quenching;secondly,temperature detection for physiological temperature based on the decrease of fluorescence lifetime caused by thermal quenching;thirdly,temperature detection for high temperature based on the change of fluorescence intensity ratio?FIR?caused by thermal coupling energy levels.The first chapter is the introduction part of this paper,mainly introduced the research significance,the research background and the developing status to study the influence of thermal quenching and thermal coupling level on the luminescence performance of fluorescent light-emitting materials.Firstly,we introduced the basic knowledge of the fundamental spectroscopic principle and common characterization methods.At the same time,the main method for temperature measurement based on fluorescence luminescence was introduced.Besides,the basic knowledge of the thermal quenching and thermal coupling energy level were also introduced.Finally,this paper introduces some common experimental methods,including high-temperature solid-state reaction method,hydrothermal method and sol-gel method,as well as commonly used experimental equipment.The second chapter focuses on the luminous properties of the self-activated Ba₂V₂O₇:Sm³⁺ white light LED phosphor in different temperatures.Firstly,samples with different doping concentration were synthesized via the high temperature solid phase synthesis method,and the structure were characterized by X-ray diffraction spectrum.The results show that Ba₂V₂O₇:Sm³⁺ white LED phosphors were successfully synthesized.Then we measured the excitation and emission spectra of samples with different doping concentrations at room temperature.We found that the CIE coordinates of the sample shifts gradually from blue-green to orange with the Sm³⁺ ion doping concentration increases,in which the Ba₂V₂O₇:0.05 Sm³⁺ sample excited by 365 nm emit white light at room temperature.In addition,we measured the variable temperature spectrum of Ba₂V₂O₇:0.04 Sm³⁺ samples under the excitation light of 365 nm in temperature range of 25-210 ?.The experimental results showed that a strong thermal quenching was found in Ba1.96V2O7:0.04Sm³⁺ samples.As the temperature rises,the luminescence intensity will decrease,and the chromaticity coordinates shifts gradually from bluish white?0.283,0.360?at 25? and eventually to orange?0.585,0.436?at 210?,This result shows that the thermal quenching results in the decrease of luminescence intensity and the shift of the chromaticity coordinates,making the phosphor useful for temperature detection.The third chapter focuses on the temperature measurement based on the thermal quenching phenomenon of the red phosphor LuAG:Mn⁴⁺.Firstly,LuAG:Mn⁴⁺ red phosphors was synthesized via sol gel method,and the structure was characterized by X-ray diffraction spectrum,the result confirms the LuAG:Mn⁴⁺ red phosphors were successfully synthesized.Then,we measured the excitation spectrum and emission spectrum of LuAG:Mn⁴⁺ red phosphors at room temperature,and the spectrum peaks of LuAG:Mn⁴⁺ red phosphors were marked to the corresponding transition.We measured the variable temperature spectrum of LuAG:Mn⁴⁺ red phosphors in temperature range of 37-100 ?.The results show that LuAG:Mn⁴⁺ red phosphors has stronger thermal quenching phenomenon.Finally,we detailed measured the fluorescence decay curve of mainly emission of Mn⁴⁺ ions in LuAG:Mn⁴⁺ red phosphors in temperature range of 34-110?.According to the dependence between lifetime and temperature,the date was fitted and the thermal activation energy??E?of LuAG:Mn⁴⁺ red phosphors is 5732 cm-1.In addition,according to the relative sensitivity formula,the relative sensitivity of LuAG:Mn⁴⁺ red phosphors is calculate with a maximum value of 6.35%K^-1 at 72? and a typical sensitivity of 3.75%K^-1 at 38?.According to the above results,LuAG:Mn⁴⁺ red phosphor powder is proved to be suitable for temperature detection in physiological temperature range.The fourth chapter mainly studies temperature measurement method based on fluorescence intensity ratio?FIR?in NaY?MoO₄?₂:Yb³⁺ Ho³⁺ phosphors.Firstly.NaY?MoO₄?₂:Yb³⁺ Ho³⁺ phosphors was synthesized via sol gel method,and the structure were characterized by X-ray diffraction spectrum,the result confirms NaY?MoO₄?₂:Yb³⁺ Ho³⁺ phosphor was successfully synthesized.Then,we measured the emission spectrum of NaY?MoO₄?₂:Yb³⁺ Ho³⁺ phosphors at room temperature,and the spectrum peaks of the sample were marked to the corresponding transition.The results show that the NaY?MoO₄?₂:Yb³⁺ Ho³⁺ phosphors has two group comparable emissions peaks attributed to the transition from 5F4/5S2 and 5F5 level to the ground state 5I8,respectively.Then,we measured the variable temperature spectrum of NaY?MoO₄?₂:Yb³⁺ Ho³⁺ phosphors in the temperature range 360-660 k and the fluorescence intensity ratio of thermal coupling level 5F1/5G6 and 5F2,3/3K8 calculated.According to the dependence of the fluorescence intensity ratio and temperature,the date was fitted and the energy gap of thermal coupling level 5F1/5G6 and 5F2,3/3K8 of Ho³⁺ ions in NaY?MoO₄?₂:Yb³⁺ Ho³⁺ phosphors is 1379.6 cm-1.Finally,according to the absolute sensitivity and the relative sensitivity formula based on fluorescence intensity ratio?FIR?,dependence of the absolute sensitivity and the relative sensitivity on temperature in NaY?MoO₄?₂:Yb³⁺ Ho³⁺ phosphors is calculated.The results show that during the temperature range of 360-660 K,the absolute sensitivity has a maximum value of 0.00593 K^-1 at 660 K,and relative sensitivity has a maximum value of 1.53%r K^-1 at 660 K at 360 K.According to the above results,NaY?MoO₄?₂:Yb³⁺ Ho³⁺ phosphors is a type of temperature measuring material with relatively high relative sensitivity.Finally,the paper summarizes the main contents of this paper and puts forward the prospect of the application based on thermal quenching and thermal coupling level fluorescence intensity ratio.