Research On Optical Thermometry Based On Novel Rare Earth Oxyfluoride Glass Ceramics

Temperature is a physical quantity that is often measured.Accurate measurement of temperature is particularly important for daily life and scientific research.However,traditional temperature measurement methods are not accurate enough and are not applicable in many cases,such as measuring the temperature of fast-moving objects,microscopic systems and harsh environments.Non-contact optical thermometers have received extensive attention for their excellent temperature measurement performance,and different optical thermometry techniques can be used for temperature measurement,such as fluorescence intensity ratio（FIR）,spectral line position,or temperature dependence of fluorescence lifetime.Among them,the most widely used optical thermometry technique is the fluorescence intensity ratio technique because of its higher accuracy,sensitivity and reliability than other optical thermometry techniques.In this paper,glass ceramics containing Sr₂La F₇:Yb³⁺,Er³⁺and Ba₄Yb₃F₁₇:Er³⁺nanocrystals were synthesized using aluminosilicate glass as the matrix,and their microstructure,spectral properties and optical temperature measurement properties based on FIR technology were studied.This thesis is divided into four chapters:Chapter I is an introduction to the definition of temperature,common temperature measurement techniques,different types of fluorescence thermometry,common luminescence temperature measurement systems,optical properties of rare earth materials,glass ceramics and the two material characterisation methods covered in this paper:X-ray diffraction and transmission electron microscopy.In Chapters II and III,glass-ceramics containing Sr₂La F₇:Yb³⁺/Er³⁺and Ba₄Yb₃F₁₇:Er³⁺nanocrystals were synthesised by melt quenching and subsequent heat treatment,respectively,and the microstructures of these two types of glass-ceramics were analysed.The reasons for the variation of the red-green emission ratio with the concentration of Yb³⁺/Er³⁺ions are discussed.To explore the upconversion mechanism the variation of emission intensity with excitation light power at different wavelengths was measured,the variation of fluorescence lifetime at different heat treatment temperatures and different Yb³⁺/Er³⁺ion doping concentrations was analysed,and finally the emission spectra at different ambient temperatures were measured for the analysis of the feasibility of optical thermometry.Chapter IV provides a summary of this paper,for glass ceramics containing Sr₂La F₇:Yb³⁺/Er³⁺nanocrystals the relative sensitivity S_R reaches a maximum value of0.132%K^-1 at 510 K.For glass ceramics containing Ba₄Yb₃F₁₇:Er³⁺nanocrystals the relative sensitivity S_R reaches a maximum value of 0.20%K^-1 at 450 K.The shortcomings of this thesis are pointed out and there is still some work to be done,such as studying the effect of glass composition on microstructure and spectra and comparing the advantages and disadvantages of different optical temperature measurement methods.