The Design Of Four Typical Rare Earth Doped Inorganic Upconversion Luminescence Materials For Temperature Sensing

Rare-earth?RE?doped up-conversion?UC?luminescence materials have attracted much attention in the field of optical temperature sensing due to their strong anti-interference ability,high spatial resolution and non-contact measurement methods.However,the low UC luminencence efficiency limits its wide application in this field.The aim of this thesis is to develop a novel UC luminescent material that is efficient and can be used in optical temperature sensing.Four typical inorganic compounds(concluding,SrF₂,Ca₉Y?PO₄?₇,Bi_0.5Gd_1.5O₃ and Gd₆O₅F₈)were selected as the matrix.The micro/nanomaterials doped with RE ions(Yb³⁺,Tm³⁺,Er³⁺and Ho³⁺)with good UC luminescence properties were designed and synthesized.The UC mechanism,the regulation of emission color,the enhancement of luminescence intensity and the performance of optical temperature sensing are investigated in detail.The main research results of this thesis are as follows:1.Magnetic green UC luminescence nanomaterials SrF₂:20%Yb³⁺,2%Ho³⁺with 39nm were designed and synthesized by hydrothermal method.The magnetic and optical temperature sensing properties of SrF₂:20%Yb3+,2%Ho3+nanomaterials were studied in the temperature range of 50 K-523 K.Meanwhile,the mechanism of anomalous thermal quenching based on Yb³⁺and Ho³⁺excited at 980 nm was proposed.This work provides a new reference for the application of temperature sensing in the low and medium temperature range?50 K-523 K?in a single system.2.On the one hand,Yb³⁺/Er³⁺/Tm³⁺double/triple doped Ca₉Y?PO₄?₇ materials with micro/nano size were synthesized by high temperature solid state method and hydrothermal method,respectively.The UC yellow emission and blue emission were achieved by co-doping technique,and the dependence of UC luminescence intensity on doped ion concentration and synthesis method was systematically studied.The results show that the UC emission color of the sample depends on the synthesis routes and excitation powers.On the other hand,Yb³⁺/Er³⁺/Li⁺co-doped Bi_0.5Gd_1.5O₃ was successfully designed and synthesized via band gap engineering and energy transfer theory,which exhibit a bright pure red UC emission.The doping of Li⁺ions has greatly enhanced the red emission,which was about 9.3 times than that of the undoped ones.Under the excitation of 980 nm,we systematically studied the relationship between the single emission intensity at 662 nm of the two samples?one is doped with Li⁺and another is undoped?and the temperature from 300 K to 525 K.The concepts of energy transfer and bandgap engineering in this work provide an idea for obtaining pure red UC luminescent materials.The excellent performance of pure red UC luminescence is expected to be used as candidate materials in the fields of temperature sensing.3.Gd₆O₅F₈ micro-particles with controllable morphologies were successfully designed and synthesized by solvothermal method.The effects of synthesis parameters on morphologies and sizes were studied and the blue UC emision intensity of Gd₆O₅F₈:Yb³⁺/Tm³⁺with different morphologies were compared.It could be found that the blue UC emission intensity of Gd₆O₅F₈:Yb³⁺/Tm³⁺micro-particles with hexagonal prism shape were the best.On this basis,the luminescence mechanism of Gd₆O₅F₈:Yb³⁺/Er³⁺/Ho³⁺was illuminated through the regulation of Yb³⁺and Er³⁺and Ho³⁺ions concentrations,the dependence of UC intensity on pumping power and the fluorescence lifetime measurement.Based on the fluorescence intensity ratio technology,the optical temperature sensing performance of the fluorescence intensity ratio of Gd₆O₅F₈:Yb³⁺/Er³⁺excited by 980 nm was systematically discussed in the temperature range of 300 K-523 K.For Gd₆O₅F₈:Yb³⁺/Ho³⁺,under dual-mode exciting and emission?the emission spectrum excited by blue light at 451 nm has two emission peaks at 490 nm and 545 nm,respectively.At the same time,the emission spectrum excited by 980 nm has two emission peaks at 545 nm and 660 nm.The emission spectra generated by these two excitations are dominated by green light emission at545 nm.?,the green luminescence intensity can be significantly enhanced by Li⁺doping.In the temperature range of 298 K-523 K,the fluorescence intensity ratios of Gd₆O₅F₈:Yb³⁺/Ho³⁺/Li⁺under dual-mode exciting and emission,all showed a single exponential relationship with the change of temperature through function fitting.Therefore,based on the excellent performance of this material,Gd₆O₅F₈:Yb³⁺/Er³⁺/Ho³⁺/Tm³⁺provides a new option for temperature sensing.