| In this thesis,three different glass formulations were used,respectively 50SiO2-20A12O3-(30-n)CaF2-nCrF3,50Si02-10Al2O3-20ZnF2-(20-n)SrF2-nCrF3,and 60SiO2-20ZnF2-(20-n)BaF2-nCrF3.Different concentrations of Cr3+-doped fluorosilicate glass were prepared by high-temperature melting method.Thermal analysis(DTA),X-ray powder diffraction(XRD)and transmission electron microscopy(TEIM)were used to study the heat treatment of the glass structure and micro-morphology.Through the transmission spectrum,steady-state spectrum and fluorescence lifetime test methods,the position of Cr3+ in the glass matrix was studied.By fitting a series of fluorescence lifetimes to the corresponding temperatures,relevant parameters about the temperature sensing performance of the test sample are obtained.In the strong field environment,the lowest excitation energy level of Cr3+ is 2E,and in the weak field environment,the one is 4T2.The Cr3+ in the weak field environment has a good measurement to the lower temperature,and the Cr3+ in the strong field environment has a better measurement for the higher temperature.And there are usually two kind of octahedron in the fluorosilicate glass,oxygen octahedron and fluorine octahedron,the former is a strong field,and the latter is a weak field.Therefore,by providing two crystal field environments forCr3+ ions in glass ceramics,and optimizing the coordination environment of Cr3+ through heat treatment,dual-mechanism temperature sensing could be realized through single-doping Cr3+,broadening the temperature sensing range.We also noticed that the Cr element in glass usually coexists in many valences.And the fluorescence lifetime of Cr4+ also has a relatively high relative temperature sensitivity index.It is possible that Cr4+ can stably coexist with Cr3+ through measures such as crystallization and valence state adjustment,so that the two ions of Cr element can be used together for temperature measurement to realize multi-mode temperature sensing.1.Controllable precipitation of uniformly distributed CaF2 nanocrystals in a Cr3+single-doped 50SiO2-20Al2O3-(30-n)CaF2-nCrF3 glass system was achieved.Spectral experiments confirmed that there are two kinds of emission centers in glass ceramics,and the corresponding emission peaks are in the red and near-infrared regions,which are the fluorescence of Cr3+ in oxygen and fluorine octahedron,respectively.The fluorescence lifetime measurements from room temperature to 300 ° C were performed on these two kinds of fluorescence,and the correspondence fluorescence lifetime was obtained.The relative temperature-sensitive coefficient of fluorescence lifetime at 724 nm in the red region reaches a maximum of 0.76%K'1 at 498K.The relative temperature-sensitive coefficient of fluorescence lifetime at l u m in the near-infrared region reaches a maximum of 0.47%K'1 at 351 K.2.ZnA12O4 nanocrystals,which can provide a strong crystal field environment for Cr3+,have been obtained in the GCSr CrO.100-1 sample of 50SiO2-10Al2O3-20ZnF2-(20-n)SrF2-nCrF3 system due to the severe volatilization of F element.Wide spectrum fluorescence of Ctr4+ was observed near 1196 nm in the near infrared region.In this sample,the relative temperature-sensitive coefficient of fluorescence lifetime(at 711 nm)of Cr3+ in the O-coordinating environment reaches a maximum of 0.71%K-1 at 611 K;the relative temperature-sensitive coefficient of the fluorescence lifetime(at 1196 nm)of Cr4+ reached a maximum value of 1.54%K'1 at 365 K.In addition,the sample uses the energy transfer betweenCr3+ and Cr3+ that should be avoided under normal circumstances,achieving single-excitation dual-mode temperature sensing,further reducing the cost of temperature sensing.3.GCBa Cr0.050 sample were selected in the 60SiO2-20ZnF2-(20-n)BaF2-nCrF3 system for fluorescence lifetime testing under low temperature conditions.The relative temperature-sensitive coefficient of fluorescence lifetime(at 724 nm)of Cr3+in the O-coordination environment reaches a maximum of 0.58%K-1 at 317 K5 and the relative temperature-sensitive coefficient of fluorescence lifetime(at 988 nm)of Cr3+ in the F coordination environment reaches a maximum of 0.47%K-1 at 184 K.Using the temperature sensing of Cr3+ in two coordination environments improves the temperature measurement accuracy in the overlap region of the temperature-sensitive curves,and ensures that the temperature sensitivity coefficient is higher in this interval. |
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