The Research On Temperature Sensing Based On FIR Technique Of Rare-Earth Doped Composite Oxide Materials

Temperature is one of the basic thermodynamic parameters,and its accurate measurement plays an essential role in industrial production,scientific research,life medicine and daily life.Traditional contact temperature sensing has an extremely important role in many fields.However,these traditional contact thermometers are unable to meet the measurement requirement in many cases such as electromagnetic interference,corrosion environment,biological cells and fast moving objects due to the limitation of their internal mechanism.Therefore,it is significant to develop a new type of non-contact temperature sensing,which can be applied and have a fat respond under special conditions.As a promising non-contact temperature measurement method based on fluorescence intensity ratio?FIR?technology has paid more attention in recent years due to its advantages independent on power fluctuation of excitation source,the number of luminescence center and fluorescence loss.With the development of nanotechnology,rare earth doped oxides have shown great potential application in biological tissues or cells due to their advantages such as excellent luminescence performance,good stability,low toxicity,small size and low fluorescence interference.Here,LuNbO₄,KLa?MoO₄?₂,YPO₄ were selected as the matrix,and Pr³⁺,Tb³⁺,Nd³⁺,Yb³⁺,Er³⁺ions as dopants.A series of up or down conversion materials with excellent luminescence and temperature sensing properties were synthesized through high temperature solid state and hydrothermal processes.The contents are mainly divided into the following three parts:In chapter three,LuNbO₄:Pr³⁺/Tb³⁺block down-conversion materials were synthesized by high temperature solid state method.Under intervalance charge trasnsfer?IVCT?at 305 nm excitation,the sample simultaneously shows green emission from ⁵D₄?⁷F₅ transition of Tb³⁺and red light from ¹D₂?³H₄ transition of Pr³⁺.The temperature dependent fluorescence intensity ratio of Pr³⁺and Tb³⁺was calculated according to their photoluminescence spectra in the range of 283-493 K.The optical absolute sensitivity and relative sensitivity are 0.024 K^-11 and 1.26%K^-1,respectively.In chapter four,square-like micro structure KLa?MoO₄?₂:Yb³⁺/Er³⁺up-conversion materials were synthesized by hydrothermal method to avoid damage to biological tissue caused by high-energy ultraviolet light?305 nm?excitation and to prevent the block material from entering cells due to its excessive size.The optimal luminescence sample is KLa?MoO₄?₂:10%Yb³⁺/2%Er³⁺.Under 980 nm excitation,the emission spectra are mainly composed of strong green light and weak red radiation,which are from the ²H_11/2/⁴S_3/2?⁴I_15/2,⁴F_9/2?⁴I_15/25/2 transitions of Er³⁺,respectively.The FIR based on the two thermal coupled levels(²H_11/2/⁴S_3/2)emitting of Er³⁺are investigated to detect the temperature sensing performance,and their absolute sensitivity reached 0.017 K^-1at 493 K.It is also proved that the doping concentrations of Yb³⁺,hardly have effect on the temperature sensing sensitivity.In chapter five,rice-like nanoparticles YPO₄:Nd³⁺/Yb³⁺/Er³⁺up-conversion were prepared by simple hydrothermal method,in which Nd³⁺with a large absorption cross-section at 808nm were used as the sensitizer to avoid biological tissue thermal damage by excessive absorption of water at 980 nm.Under 808nm excitation,the up-conversion luminescence mechanism of the samples are investigated,in which the Nd³⁺?Yb³⁺?Er³⁺energy transfer process plays an important role.The sensitivity of YPO₄:Nd³⁺/Yb³⁺/Er³⁺and YPO₄:Yb³⁺/Er³⁺were calculated in a comparable method based on the temperature-dependent FIR from thermal coupling levels of Er³⁺(²H_11/2/⁴S_3/2?⁴I_15/2)with the excitation of 808and 980 nm laser,respectively.It is found that the energy gap??E?is influenced owing to the energy back transfer?EBT?from Er³⁺to Nd³⁺in the three-doping system compared to the double-doping system,but their absolute sensitivities have no obvious change.The optical absolute sensitivity of YPO₄:Nd³⁺/Yb³⁺/Er³⁺is 0.0029 K^-1,which proves that the materials have potential temperature sensing application in biomedical field.