Non-contact Optical Thermometry Based On Different Mechanisms Using Lanthanide Doped Phosphors

Temperature is the key variable of thermodynamic state and it has significant influence on industrial development,scientific research,life operations and other aspects.Therefore,precise measuring of temperature has been an important subject.A variety of temperature sensors are also widely used in daily life,metrology,gas mechanics,atmosphere and maritime,chemistry,medicine,biology and military technology.With the rapid development of energy,information,biomedicine and other fields,higher and more complex requirements are put forward for the speed and accuracy of temperature detection,such as submicron and even nanoscale temperature measurement,cell temperature detection in organism,etc.However,the detection speed and accuracy of traditional thermometers are greatly limited,and usually can only meet the temperature measurement for objects of 10 microns and above.In this case,the realization of non-contact temperature detection based on optical sensor can overcome the inherent shortcomings of the traditional contact thermometer and have gained the significant interest from the research scientists.It can meet the measurement requirements of non-contact,high spatial resolution,fast response real-time detection.In a certain temperature range,some optical properties of luminescent materials or ions,such as peak position,fluorescence intensity ratio,spectral linewidth,fluorescence intensity,polarization anisotropy and fluorescence decay lifetime,change with the change of temperature.Therefore,the change of these optical properties can be used to measure the temperature.In the first chapter,we have illustrated the importance and research background of non-contact optical thermometry as well as basic concepts of luminescence and its types.Furthermore,the basic knowledge and principle of rare earth doped luminescent materials are briefly introduced,including rare earth elements,spectrum theory,rare earth luminescent materials,up conversion luminescence,glass-ceramics,and common spectral characterization methods,etc.The chapter two reviews the most important results obtained from the papers of our lab along with other labs paper,in which different temperature sensing methods via luminescence intensity ratio of thermally coupled energy levels of lanthanide ions,temperature-dependent decay time,optical thermometry via temperature-induced spectral shift of the charge transfer band edge of lanthanides doped ReVO4(Re=Gd,Lu,Y)phosphors and temperature sensing method based on the thermally populated low lying energy levels of Sm3+,Eu3+,Ho3+,and Tb3+ doped phosphors have been summarized.The physical mechanism,thermoluminescence characteristics,temperature detection range,and sensitivity of the materials are discussed in detail.The advantage and disadvantages of each approach have been compared.Finally,a further research direction based on temperature sensing has been suggested.In chapter three,temperature sensing performance of GdVO4:Eu3+phosphors have been studied using a method based on thermal coupling of the low-lying levels(7F(?)J=0,1,2)of Eu3+.GdVO4:Eu3+phosphors,which exhibits the outstanding luminescence characteristics with temperature and high detection sensitivity.Luminescence intensity ratio has been investigated between the 5D0?7F4 emission intensities when 5D0 state is reached by excitation from thermally populated low-lying excited states 7F1 and 7F2.The luminescence intensity ratio monotonously increases with rising of temperature from 133 K to physiological temperature of 313 K.Specifically,the maximum value of relative sensitivity SR reach to 6.73%K-1 for first scheme and 2.87%K-1 for second scheme.The GdVO4:Eu3+phosphor shows the excellent relative sensitivity of 1.23%K-1 in physiological temperature range(310 K),recommending its potential for applications in bio-medical field.