Absorption Spectroscopic Temperature Sensing Based On Solid Rare Earth Oxides

Temperature has a significant effect on the absorption spectra of solid rare earth materials.The use of absorption spectrum for temperature sensing can be a branch of optical sensors,which has attracted much attention in the field of science and engineering.In this paper,a ratiometric method was applied on the temperature dependent absorption spectra of Ho₂O₃,Er₂O₃ and Nd₂O₃ according to the boltzmann's law.Some thermally coupled energy levels of the oxides were identified.Temperature sensing characteristics of the built system were evaluated,including sensitivity,relative sensitivity,resolution and repeatability.Moreover,Ho₂O₃ was used as a temperature probe for a electric stove,which could be an example of absorption intensity ratio technique for high temperature monitoring.In the experiments,a halogen tungsten lamp was used as the light source.The spectroscopic setup employed a reflective light path.The in-use fiber optical spectrometer has a resolution of 0.5 nm.Spectroscopic data processing presented the relationship between lnR?natural logarithm of the absorption peak intensity ratio?and1/T?reciprocal of temperature in Kelvin?.Main findings of the research are as following.?1?Ho₂O₃ offered temperature sensing equations as lnR=0.243+311.7*?1/T?where R=I?650.0nm?/I?669.0nm?,and lnR=0.800-256.7*?1/T?where R=I?465.3nm?/I?650.0nm?.Resolutions of them were 3.2×10^-55 k^-11 and-4.7×10^-55 k^-1,respectively.Repeatability of them were 3.6%FS and 4.9%FS,respectively.?2?Er₂O₃ offered temperature sensing equations as lnR=0.023+140.7*?1/T?where R=I?522.8nm?/I?539.7nm?,and lnR=0.560-271.1*?1/T?where R=I?539.7nm?/I?652.6nm?.Resolutions of them were 5.7×10^-55 k^-11 and 2.2×10^-55 k^-1,respectively.Repeatability of them were 3.88%FS and 3.87%FS,respectively.?3?Nd₂O₃ offered temperature sensing equations as lnR=0.621-172.8*?1/T?where R=I?584.3nm?/I?738.9nm?,and lnR=-0.611+116.8*?1/T?where R=I?465.3nm?/I?650.0nm?.Resolutions of them were-4.1×10^-5k^-11 and 5.1×10^-55 k^-1,respectively.In addition,the absorption spectra and emission spectra of broadband fluorescent material YAG:Ce were applied to temperature sensing with the band barycenter and peak wavelength charactering.After data processing,sensing equations and some sensing characteristics were summarized as following.?1?AbsorptionspectrumsensingequationsweredecidedasY=473.11-0.076X+0.000147X²?barycenter?and Y=460.28-0.020X+0.000019X²?peak wavelength?.The barycenter method has a resolution as 3.3?and repeatability as2.1%FS.?2?Emission spectrum sensing equations were decided as Y=564.14+0.0199 X?barycenter?and Y=542.25+0.022 X?peak wavelength?.The barycenter method has a resolution as 2.0?and repeatability as 1.3%FS.Ho₂O₃ temperature probe was used for monitoring high temperature above 300?.It showed a finer precision than the blackbody irradiation temperature measurement method,promising it a candidate method for high temperature sensing.YAG:Ce offered multiple temperature sensing functions.The spectral band barycenter shift can be measured with a better precision than the peak wavelength.