The Preparation Of Rare Earth Doped Several Indiumate Phosphors And The Study Of Their Temperature Sensing Properties

In recent years,up-conversion luminescent materials occupy a very important position in rare earth luminescent materials.It is a nonlinear optical process that emits visible emissions under the near-infrared excitation.It converts near-infrared light into visible light through multi-photon mechanism.Its characteristic is that the photon energy of absorbed is lower than the energy of the emitted photons.Up-conversion luminescent materials have important applications in diminutive solid-state lasers,white light emitting diodes,biomarkers,anti-counterfeiting technology,fluorescent probes,bio-imaging,temperature sensing.Temperature is an essential parameter of thermodynamics,which also plays vital role in many fields.Therefore,how to achieve the accurate temperature measurement has prompted significant attention.The early thermometers were made from the thermal expansion and contraction of air.With the developments of science and technology,the temperature measurement technology is improving as well.Owing to the increasing of temperature measurement range and different requirements,many types of thermometers are manufactured,such as gas thermometers,resistance thermometers,thermocouple thermometers and high temperature thermometers,etc.However,these thermometers must be in direct contact with the object being measured.In nowadays society,people are demanding more and more precise control and detection of temperature.The demand for sensors is increasing,the traditional contact temperature measurement method has been unable to meet the requirements of temperature measurement.So the research on sensing mechanism is gradually deepening,the temperature can be directly detected by noncontact temperature sensors using optical parameters,for instance,single fluorescence intensity,fluorescence intensity ratio(FIR),emission bandwidth,fluorescence lifetime,and so on.Optical temperature detection based on rare earth luminescent materials is a better non-contact temperature measurement method,and one of our research objectives is to develop a new type of FIR temperature measurement material.Among them,rare earth doped up-conversion luminescence materials are typical.Fluoride is usually the preferred upconversion material due to its high ionicity and low phonon energy.However,fluorides are usually poisonous and harmful to the environment,which could limit their applications.Accordingly,oxides generally exhibit superior chemical stability and eco-friendly features.The indium salts have lower phonon energy,which can enhance radiative transition probability to achieve up-conversion luminescence.Considering the above requirements for sensing mechanism,in this paper,the main results are concluded as follows:1.The first part of the work:the luminescence properties and temperature sensing mechanism of Yb3+/Ln3+(Ln=Er,Ho)rare earth ions doped Ba2In2O5 phosphors were studied.A series of Yb3+/Ln3+(Ln=Er,Ho)up-conversion samples with different doping concentration were synthesized by high temperature solid state method.The luminescence properties of the prepared samples were studied by optimizing the doping concentration of rare earth ions,and the luminescence mechanism was analyzed in detail.The samples have obvious visible and near infrared emission under the 980 nm excitation.The luminescence mechanism of up-conversion materials was analyzed according to the relationship between luminous intensity and excitation pump power.The temperature-dependence up-conversion emission spectra of the samples were measured in the temperature range of 298-573 K.The FIR of two thermally coupled levels was calculated.The relationship between fluorescence intensity and temperature was plotted.The corresponding sensitivity was calculated.The relationship between sensitivity and level gap was also studied.2.In the second part,optical properties and temperature sensing properties of Sr2+substituted Ba2In2O5:Yb3+/Ln3+(Ln=Er,Ho)fluorescent materials were studied.Sr2+ions were introduced into the structure;the luminescence properties of the samples were studied by controlling the doping concentration of Sr2+and rare earth ions,and the luminescent properties of rare earth doped Ba2In2O5 fluorescent materials were optimized.By changing the excitation power density,the luminescence intensity was affected,and the corresponding relationship curve was drawn to study the luminescence mechanism of rare earth ions in the material.The temperature-varying spectra of the material were analyzed,and the relationship curves of FIR in abscissa and temperature change in longitudinal coordinate were obtained,and the corresponding sensitivity was calculated.3.The third part of the work,the In6Ti6CaO22 fluorescent material with Er3+/Ho3+as the activation center and Yb3+as the sensitizer was studied.In6Ti6CaO22:Yb3+/Ln3+(Ln=Er,Ho)fluorescent materials were also prepared by high temperature solid state method.By means of phase analysis and fluorescence spectrum analysis,the following conclusions were drawn:the optimum doping amount of activators for In6Ti6CaO22:Yb3+/Er3+,In6Ti6CaO22:Yb3+/HO3+phosphors is 0.04 mol,and the optimum doping concentration of sensitizer ions is 0.19 mol and 0.21 mol,respectively.Under the excitation of 980 nm laser,the thermal properties of phosphors between 295-495 K have been studied systematically,and the temperature sensing properties were also studied deeply.The results show that In6Ti6CaO22:Yb3+/Ln3+(Ln=Er,Ho)phosphors are also a good up-conversion luminescent material,which has good temperature sensing performance.