Preparation And Optical Temperature Sensing Properties Of Er³⁺/Yb³⁺ Codoped Oxyfluoride Glass Ceramics

Temperature plays a crucial role in our lives and many industrial productions.Therefore,accurate temperature measurement is particularly important in all areas of our production and life.However,traditional temperature measurement technologies will destroy the temperature measurement environment,resulting in errors in the measured temperature.In addition,the temperature measurements are also limited under severe environmental conditions.The optical fiber temperature sensor is a new type of non-contact temperature measurement method.Among them,the optical fiber temperature sensor based on the fluorescence intensity ratio has been widely concerned because it can effectively avoid the fluorescence loss,the power fluctuation of the excitation light and the effect of electromagnetic field in the measurement process.With the continuous expansion of application fields,fluorescent materials with superior performance continue to emerge.Among them,rare-earth-doped oxyfluoride glass-ceramics have good mechanical strength and stable chemical properties,and can effectively increase the emission intensity of rare-earth ions.It is considered to be a high-quality matrix material.On the basic research of the physical properties and optical properties of Er³⁺/Yb³⁺codoped oxyfluoride glass-ceramics,a practical portable all-fiber temperature sensor was designed and builded by combining oxyfluoride glass-ceramics with fiber,which can be used to explore the temperature sensing characteristics of Er³⁺/Yb³⁺codoped oxyfluoride glass-ceramics.Er³⁺/Yb³⁺co-doped BaGdF₅ glass-ceramics were successfully prepared by melt quenching and heat treatment.The synthesis of the crystal phase was confirmed by XRD.The morphology and microstructure were observed by TEM/HRTEM.The average grain size of the crystallites was found to be 33 nm.The Eu³⁺ion successfully enters into BaGdF₅ crystallites after heat treatment by comparing the fluorescence spectrum and fluorescence lifetime before and after heat treatment.Comparing the upconversion emission intensity of Er³⁺/Yb³⁺（0.4/0.6mol%）co-doped precursor glass and the glass ceramic samples,We found that the BaGdF₅ crystal phase are favorable for upconversion luminescence of rare earth ions.The optical temperature sensing performance of the sample was investigated in the temperature range of 298K-681K.The results show that under the excitation at 980 nm with the laser power of 4mW,the absolute sensitivity is 0.0015K^?1at 567K,the relative sensitivity is 1.28%K^-1at 298K.Theβ-NaYF₄ oxyfluoride glass ceramics were prepared using the traditional melt-quenching method and the appropriate heat treatment mechanism.X-ray diffraction patterns（XRD）were used to test the precursor glass and the glass ceramic samples to confirm the formation of theβ-NaYF₄ crystal phase.The transmittances of the samples were measured to prove their high transparency.The size and morphology of theβ-NaYF₄ crystal were further analyzed by Transmission Electron Microscope（TEM）.Spherical nanoparticles were observed and the size was 25³5nm.Upconversion luminescence spectrum of the samples of Er³⁺/Yb³⁺with different concentrations codoped oxyfluoride glass ceramics was obtained.It was found that the luminescence intensity of Er³⁺/Yb³⁺（1/1mol%）codoped oxyfluoride glass ceramics is the strongest.Based on the above test results,in the temperature range of298K-824K,the temperature sensing characteristics of the Er³⁺/Yb³⁺（1/1mol%）codopedβ-NaYF₄ glass-ceramic sample were studied.It was found that at 545K,the highest absolute sensitivity was obtained is 0.0029K^-11 and the relative sensitivity was1.25%K^-1at 298K.The Er³⁺/Yb³⁺co-dopedβ-NaY（Gd）F₄ glass-ceramics were successfully prepared by traditional melting quenching and heat treatment.The T_g,T_f and thermal expansion coefficients of the glass before and after the heat treatment were tested to characterize the thermal properties.In addition,XRD,TEM/HRTEM methods were used to confirm the synthesis of the crystal phase,the morphology,size and microstructure of the nanocrystals.The average size of crystals is about 30⁴0nm.We studied the effects of different heat treatment regimes on the size of the generated crystallites and the influence of different doping concentrations of rare earth ions on the upconversion luminescence.Finally,the Er³⁺/Yb³⁺（0.2/0.4mol%）co-dopedβ-NaY（Gd）F₄ glass-ceramic sample after heat treatment at 650^oC for 2h was selected for further study.The optical temperature sensing performance of the sample was also investigated.The results showed that at the power of 12mW,the highest absolute sensitivity is 0.0032K^?11 at 567K,and the relative sensitivity is 1.28%K^?11 at 298K.The results above was obtained by repeating the test several times,which proves that there is a small error.The experiments show that this fiber optical temperature sensing device has the advantages of portability,low cost and good stability.So it will be applied in the field of temperature measurement.