Upconversion Luminescence Of Rare Earth Ions Codoped Calcium Tungstate Crystal And Its Temperature Characteristics

The rare earth（RE）ions play a key role in numerous fields,such as in the preparation of lasers,in the fluorescent anti-counterfeiting marks,in the fluorescence imaging of the organizations,in the track of biological macromolecular proteins,in the upconversion（UC）-based photodynamic therapy,in the three-dimensional images,in the display and lighting markets,in the pollution sources monitoring,and so on.Among all of these fields,the fluorescence intensity ratio（FIR）technology for measuring the temperature based on the RE ions,which possesses lots of advantages of relatively high thermometry sensitivity and fast time response,etc.,has been a vital and promising branch,attracting the researchers’ sufficient attention.However,lots of work needs to do further.For one thing,it is found that it has been a heat issue that using Stark split energy levels of some kind of RE ions via FIR technology for measuring the temperature,but the corresponding researches are not deep enough to make it clear what the parameters and performance can it obtains in reality.For another thing,as a member of FIR thermometry methods,the newly-emerged valley to peak ratio（VPR）method on the basis of RE ions owns its special merit,but there are no literature concerning about utilizing UC luminescence to achieve VPR technology for temperature measurement.In addition,the application conditions of VPR method are extremely rigorous and the relatively simple one is still on the way.These problems,which extremely confine the practical application and further development of FIR technology,need to be resolved timely and thoroughly.This dissertation takes RE ions-codoped calcium tungstate polycrystalline powders as the object of study,focusing on two parts of work,namely the practical value of FIR technology based on Stark split energy levels of some kind of RE and the realization of VPR method through UC luminescence.The practical value and the performance of FIR technology utilizing Stark split energy levels of some kind of RE ions have been investigated in detail.Based on the Yb³⁺-Er³⁺ codoped calcium tungstate polycrystalline powders,the typical green and red UC luminescences of Er³⁺ were detected with the help of 980 nm near infrared（NIR）diode pump source.The Stark split energy levels of 4S3/2 state of Er³⁺ and the Stark split energy levels of 4F9/2 state of Er³⁺,as well as the 2H11/2/4S3/2 states of Er³⁺ were used to monitor the temperature successfully,and the maximum relative sensitivities obtained are 0.21%K-1,0.27%K-1,1.15%K-1,respectively.Through comparing the temperature detection uncertainty,it was found that using Stark split energy levels of 4S3/2 state of Er³⁺ obtained the largest temperature detection uncertainty,and using Stark split energy levels of 4F9/2 state of Er³⁺ obtained the second largest value,while using 2H11/2/4S3/2 states of Er³⁺ obtained the smallest temperature detection uncertainty.The experimental results suggest that the larger the relative sensitivity,the smaller the temperature detection uncertainty.Therefore,it is a must that searching for thermally coupled energy levels which own larger relative sensitivities if someone wants to obtain a smaller temperature detection uncertainty.The realization of VPR method based on UC luminescence of RE ions has been investigated in detail.On the basis of the Yb³⁺-Er³⁺ codoped calcium tungstate polycrystalline powders,the green UC luminescence of Er³⁺ was used to achieve VPR method for temperature sensing for the first time,with the help of 980 nm NIR diode pump source.It indicates that the potential stray light originating from the short-wavelength laser could be avoided.The maximum relative sensitivity is about 0.40%K-1.Using the red UC luminescence of Er³⁺ could also detect the temperature and the obtained maximum relative sensitivity was 0.19%K-1,and it extremely simplified the applied conditions and expended the applied range of VPR method.