Study On Optical Temperature Measurement Based On Fluoride Fluorescent Glass Ceramics

Optical temperature measurement is the main technical means to achieve non-contact measurement in harsh environments,and it has received extensive attention for its advantages of safety and high sensitivity.Fluoride optical glass ceramics have low phonon energy,narrow luminous peaks,high luminous intensity and efficiency,are excellent optical temperature measuring materials,and have a wide range of technical application prospects.In this paper,fluoride optical glass ceramic is selected as the main body of the device,and the optical temperature measurement performance is studied by changing the type,structure,rare earth doping type and concentration,excitation power and other methods.In order to reduce the error of optical temperature measurement,based on the finite element algorithm,we studied the effect of laser heat conduction in fluoride ceramics on its optical temperature measurement,and gave a correction method.The specific research of this paper are as follows:The first chapter,the introduction part introduces the research background of rare earth doped glass ceramics,the mechanism of photoluminescence,the mechanism of precious metal regulation of rare earth luminescence,the mechanism of light temperature sensing,as well as the fluorescence intensity ratio technology and fluorescence lifetime temperature measurement technology.The second chapter,in order to overcome the adverse effect of noise signal in the process of optical temperature measurement,we successfully prepared?-Na YF₄:Dy³⁺transparent glass ceramic with high luminous efficiency by melt quenching method.The structure,spectrum and light temperature sensing performance of?-Na YF₄:Dy³⁺glass ceramics regulated by doping precious metal Ag are proposed.The parameters such as fluorescence intensity,spectral color,fluorescence intensity ratio,temperature sensitivity,and fluorescence lifetime were observed to depend on Ag concentration under 355nm excitation.When 0.5mol%Ag is added,the optical temperature sensitivity?-Na YF₄:Dy³⁺glass ceramics is increased by 35%.In this chapter,a new method of adjusting fluorescence intensity and improving temperature sensitivity is proposed by incorporating precious metal Ag into?-Na YF₄:Dy³⁺glass ceramics.The third chapter,the idea of adjusting the temperature measurement performance of rare earth glass ceramics by constructing nano-core shell structure is proposed.We successfully prepared a new transparent glass ceramic with Ag@Na Gd F₄:Er³⁺core-shell structure nanocrystal inlay by melt quenching method.X-ray diffraction and transmission electron microscopy images showed that the precious metal Ag was successfully wrapped by spherical Na Gd F₄:Er³⁺nanocrystals,forming an Ag@Na Gd F₄:Er³⁺core-shell structure in the glass matrix.Compared with the traditional Na Gd F₄:Er³⁺glass ceramic,the emission intensity of Ag@Na Gd F₄:Er³⁺core-shell structure glass ceramic is greatly improved.By changing the Ag concentration,the fluorescence emission intensity,the fluorescence intensity ratio of the thermal coupling level(²H_11/2/⁴S_3/2)and the temperature sensitivity can be effectively controlled.When doped with 0.15mol%Ag,the relative sensitivity S_Rof Ag@Na Gd F₄:Er³⁺core-shell structure glass ceramic reaches the maximum,which is 20%higher than that of Na Gd F₄:Er³⁺glass ceramic.This work proposes a new method to enhance the emission intensity and optical temperature measurement performance by growing nano-core-shell structures in glass ceramics.The fourth chapter,through the work in the first two chapters,we find that the thermal effect of the excitation light itself will cause errors in the glass ceramic optical temperature measurement.In order to solve this problem,this chapter is based on the finite element method algorithm,using Matlab programming to study the heat conduction process of excitation light in fluoride glass ceramics.A three-dimensional heat conduction model was established to study the thermal effect.When the continuous laser excitation power is 1W,the temperature of the spot on the Ca F₂ ceramic surface increases by 29K after irradiating for one second,which proves the heating effect caused by the continuous laser irradiation,which affects the measurement accuracy of the light temperature of the glass ceramic.We have studied the influence of these parameters on temperature by changing the parameters such as laser power,laser spot radius,ceramic absorption coefficient,excitation source excitation mode and so on.It was found that the temperature increase was proportional to the laser power and the absorption coefficient of the ceramic,and inversely proportional to the laser beam radius.Using a 10ns pulse laser as the excitation source,it was found that the temperature increase was 48%lower than that during continuous laser excitation.This shows that the pulsed laser can effectively suppress the heat conduction effect and improve the accuracy of optical temperature sensing.Therefore,we have revised some important formulas in the process of light and temperature sensing.