Optical Temperature Sensing Based On The FIR Between Rare Earth Ions(Tb³⁺,Dy³⁺) And Mn⁴⁺ Ions

As a very important thermodynamic parameter,the measurement of temperature has received widespread attention.At present,traditional temperature sensing could hardly meet the various requirements of various industries,where temperature sensors with faster response speed,higher measurement accuracy and better spatial resolution are demanded.The optimization of parameter's on traditional temperature sensors is not enough.Researchers have turned their attention to optical temperature sensing,which can satisfy the needs mentioned above.And its core component is luminescent material whose properties change with temperature,such as the intensity of absolute fluorescence intensity,the fluorescence decay life,the position of the luminescence peak,emission bandwidth,the rise time,the ratio of the fluorescence intensity of the two luminescence peaks,among others.These properties can change with temperature in a certain temperature range,monotonically and significantly.The temperature can be calibrated according to the measurement of these properties.The luminescent materials under study in this work are phosphors.The size of phosphor particles is very small,and the time required for the object to reach thermal equilibrium is short,so the response speed is faster.Luminescence materials can be made as nanoparticles,so the particles will be smaller and can be used for temperature measurement on a micro-scale.For example,nanoparticles can be injected into a living body,the luminescence of the material will offer the temperature information of the cells,which is very useful for studying the relationship between cell canceration and temperature.The first chapter is the introduction of the thesis,mainly include the background and significance of this research,related concepts(such as:luminescence,rare earth ions),the characteristics of luminescence of rare earth ions,and some non-contact temperature sensing techniques.In chapter two,we introduced a temperature sensing scheme based on the fluorescence intensity ratio of the co-doped activator.Mn4+ and Tb3+singly doped and Mn4+/Tb3+co-doped lutetium aluminum garnet phosphors(Lu3Al5O12,or simply LuAG)were synthesized and investigated for the application of optical thermometry.X-ray powder diffraction and luminescence spectroscopy measurements were performed on all samples to analyze their crystal phases and the sources of the luminescence peak.And the luminescence spectroscopy prove that there is no energy transfer between Mn4+and Tb3+.In particular,temperature-dependent luminescence of the LuAG:Mn4+/Tb3+sample was measured at the temperature range of 270-420 K The results showed that the ratio of luminescence intensity of Mn4+ and Tb3+has gone through a remarkable decline with the rise of temperature.And then the relative sensitivity curve is obtained.Finally,we propose a mechanism to explain why the fluorescence intensity of Mn4+ions changes rapidly with temperature,and corroborate our mechanism with the dependence of the fluorescence lifetime of Mn4+ions on temperature.In order to explore more possibilities of fluorescence intensity ratio,we introduced temperature sensing scheme based on the fluorescence intensity ratio of the mixture in Chapter 3.This chapter also deals with temperature sensing schemes based on fluorescence lifetime.We prepared Li2TiO3:Mn4+phosphor and Y2O3:Dy3+phosphor by high temperature solid phase method and combustion method,respectively.And then three mixture samples are obtained by mixing them at different ratios.After that,the temperature-dependent spectra of three samples were measured,the fluorescence intensity ratio was fitted to obtain the sensitivity of temperature sensing.Considering the emission of Mn4+ions in the biological window,the fluorescence lifetime of Mn4+ ions also measured.Finally,the reason for the difference in sensitivity between fluorescence intensity ratio and fluorescence lifetime is discussed.It provides a new idea for non-contact optical temperature sensing.At the end of the thesis,we summarized the main results and prospected the using of non-contact optical temperature sensing.