Study On Temperature Characteritics Based On Fluorescence Intensity Ratio Of Rare Earth Ions Doped Upconversion Luminescent Materials

Rare earth doped upconversion luminescent materials have a broad application prospect in the field of optical temperature measurement,such as non-contact temperature measurement,strong anti-interference ability,rapid response,high spatial resolution and other characteristics.Therefore,it has broad application prospects in optical temperature measurement.Upconversion luminescent materials have been widely reported in optical temperature measurement,but the quantitative analysis of temperature dependent upconversion luminescence mechanisms is rarely reported.Accurate temperature measurement and increased temperature sensitivity have always been the direction of many researchers.The main contents of this thesis are as follows:Firstly,Yb³⁺/Ho³⁺,Yb³⁺/Tm³⁺codoped Na Lu F₄ nanocrystalline materials synthesized by solvothermal method,the morphologys and structures of the samples were characterized by XRD and SEM.In order to prevent the nanocrystals oxidation at high temperature,the nanocrystals were poured into a hollow silica fiber tube.Rare earth nano-crystalline-hollow fiber microwaves were obtained by heating and stretching method.The waveguide characteristics are discussed.The application of microwave guidance to temperature sensing is studied.The temperature-dependent up-conversion emission spectra of Na Lu F₄:Yb³⁺/Ho³⁺-hollow fiber micro-waveguide and Na Lu F₄:Yb³⁺/Tm³⁺hollow fiber microwaveguide were measured over a wide temperature range.The fluorescence intensities of the thermal coupling energy levels ⁵F₅,⁵F₄/⁵S₂?⁵I₈,⁵I₇ and ⁵F₅,⁵F₄/⁵S₂?⁵I₈ to ⁵I₈ of Ho³⁺ions and non-thermal coupling energy levels ¹D₂ and¹G₄ of the Tm³⁺ion were analyzed.The maximum relative sensitivity of Ho³⁺ion is 1.53%K^-1and 0.9%K^-1at room temperature 300 K,respectively.The results show that the thermal coupling levels ⁵F₅ and ⁵F₄/⁵S₂?⁵I₈ of Ho³⁺ions is more suitable for temperature sensing.The maximum absolute sensitivity of the Tm³⁺ion is 0.0047 K^-1at 525 K.The results demonstrate that Tm³⁺ion is more suitable for higher temperature sensing.Secondly,the Ba Zr O₃:Ho³⁺/Yb³⁺phosphor was prepared by solid state method and the Ba Zr O₃:Ho³⁺/Yb³⁺ceramics were prepared by dry pressure method.The upconversion fluorescence of Ho³⁺ions were studied under the pump of 980 nm semiconductor laser.The fluorescence intensity ratio and relative sensitivity of Ba Zr O₃:Ho³⁺/Yb³⁺ceramics were studied at different doping concentration and pump power.The maximum relative sensitivity is obtained under different conditions.Under the pump power of 90 m W,the relative sensitivity is as high as 36.35%K^-1with 0.5mol%of the doping concentration of Ho³⁺ions in the fluorescence intensity ratio of NIR and green.The breakthrough of the sensitivity of the non-thermal coupling energy level to the temperature sensing is testified.Lastly,a high precision and wide range temperature measurement method is carried out by the upconversion fluorescence of Ba Zr O₃:Yb³⁺/Er³⁺ceramics.Using fluorescence intensity ratio technology,we analyzed the measurement temperature characteristics of nonthermal couple levels with ⁴F_9/2?1??⁴I_9/2and⁴S_3/2?⁴I_9/2under different pump power in the range of 300 K to 500 K.The results illustrate that the maximum sensitivity and the highest resolution are present at the nonthermal couple level with ⁴F_9/2?1??⁴I_9/2in the 90 m W pump power which the values were 1.39 K^-1%and 0.31 K.High accuracy of temperature measurement results from a high and comparable signal-to-noise ratio with two fluorescences by using fluorescence intensity ratio measurement.This high-precision with large-scale temperature measurement method is beneficial to accurate monitoring of the temperature changes.