Research On Luminescence Kinetics And Temperature Sensing Characterization Of Rare Earch And Transition Metal Co-Doped Fluorescent Materials

Temperature is an important thermodynamic state parameter that has significant impacts on life activities,industrial production,scientific research,and other fields.With the advancement of technology,there are increasingly stringent requirements for temperature monitoring,and various temperature monitoring technologies have emerged in different temperature measurement fields.Meanwhile,achieving fast,stable,and accurate temperature measurement is also a goal pursued by researchers.Non-contact temperature measurement based on luminescent materials has received widespread attention due to its advantages of fast response and high spatial resolution.A variety of luminescent materials,including quantum dots,organic dyes,rare earth（RE）or transition metal（TM）ions activated phosphors,have been utilized as the sensing media.In order to select suitable luminescence thermometry probes for specific application,much attention has been fixed on the thermal stability as well as the luminescence efficiency.In addition,the luminescence of thermometers should also change obviously with temperature to guarantee sensitive measurement with fine thermal resolution.Considering above requirements,the RE or TM ions doped inorganic materials would be ideal candidates because of their excellent physical and chemical stability as well as sufficient brightness under proper excitation.In this paper,we deeply investigate the luminescent and temperature sensing characteristics of rare earth-transition metal co-doped systems,and the main work of this thesis is as follows:The Gd₃A_lxGa_5-xO₁₂:10mol%Yb³⁺-1mol%Er³⁺samples have been synthesized by the high temperature solid-state method,the room temperature emission spectra were tested when the Ga³⁺/Al³⁺ratio was changed.The study found that the green luminescence of Er³⁺ions gradually increased with the increase of Ga³⁺ion doping.The sample was characterized by Raman spectroscopy,and the J-O parameters of Er³⁺ions in different mechanism materials were analyzed using the J-O theory when the Ga³⁺/Al³⁺ratio varied.This result implies that the low symmetry and strong covalent between the RE and ligands are realized by introducing Ga³⁺ions.Subsequently,Cr³⁺ions were introduced into GGG:Yb³⁺-Er³⁺system,and the XRD diffraction patterns confirmed the successful preparation of the GGG:Yb³⁺-Er³⁺-Cr³⁺sample.The up-conversion luminescence of Cr³⁺ions was successfully achieved by testing the emission spectrum at room temperature.The emission spectra of the sample at different temperatures were then tested,found that the up-conversion luminescence of Cr³⁺ions gradually increased with increasing temperature,while the luminescence of Er³⁺ions gradually decreased.Using this opposite temperature dependence,a fluorescence intensity ratio type temperature measurement was carried out,and the relative sensitivity reached a maximum value of 1.59%K^-1when the temperature reached 655 K.Using GGG as the substrate and Ho³⁺ions as sensitizers,we continue to explore the upconversion luminescence characteristics of rare earth transition group co doping systems.Gd₃Al_xGa_5-xO₁₂:10mol%Yb³⁺-1mol%Ho³⁺samples were prepared.It is found that GGG has smaller phonon energy than GAG through Raman spectroscopy.This also indicates a small lattice vibration energy in the GGG matrix,which contributes to rare earth ion luminescence.The samples room-temperature emission spectrum was tested and showed strong luminescence of the Ho³⁺ion in the GGG matrix.We introduced Cr³⁺ions into the GGG:Yb³⁺-Ho³⁺system and characterized it by XRD diffraction patterns.Cr³⁺ion up-conversion luminescence was successfully achieved at room temperature and the luminescence of Ho³⁺ions was enhanced which due to the energy transfer between Cr³⁺and Ho³⁺.We prepared YGG:Yb³⁺-Ho³⁺-Cr³⁺,GGG:Yb³⁺-Tm³⁺-Cr³⁺,and YGG:Yb³⁺-Tm³⁺-Cr³⁺samples in order to compare the luminescence effect of Cr³⁺ions in different matrices,it was found that in the YGG matrix the luminescence intensity of Cr³⁺increases significantly with increasing temperature which provided a new research direction for us.To further improve the luminescence and temperature sensing performance of Cr³⁺ions,we prepared Y₃Al_xGa_5-xO₁₂:10mol%Yb³⁺-1mol%Er³⁺samples by high temperature solid-phase method based on the previous chapter,the XRD,Raman spectroscopy,and Fourier transform infrared spectroscopy were used to characterized.At room temperature,Er³⁺ions exhibit the strongest luminescence in both green and red wavelengths in the YGG.By calculating the J-O theory parameters,we found that Er³⁺ions had better low symmetry and strong covalent in YGG matrix material,which contributed to the luminescence of Er³⁺ions.Cr³⁺ions were doped in YGG:Yb³⁺-Er³⁺and was characterized by SEM images,the energy dispersive X-ray（EDX）images（EDS）,and XRD diffraction patterns.By testing the in-situ XRD pattern of the sample,we found that the matrix lattice gradually expanded with the temperature rise,and phonon-assisted energy transfer occurred between Cr³⁺and Er³⁺ions,which also enhanced the luminescence of Cr³⁺ions with temperature increase.We performed temperature sensing performance testing by using the difference in luminescence intensity of Cr³⁺and Er³⁺ions with temperature change.The maximum relative sensitivity was about 4.38%K^-1at 423 K,which was significantly higher than the GGG system we studied earlier.