| In recent years, optical thermometry sensors based on the fluorescence intensityratio technique of rare earth fluorescent materials have huge potential applications inmany fields, such as electric power industry, biological medicine and military defense,and so on. It is becoming a hot spot of research to achieve a high precision and a widerange of temperature measurement both at home and abroad. In this thesis, sol-gelmethod was used to prepare Er3+/Yb3+codoped Y2O3nanocrystals and Er3+/Yb3+codoped Y2O3ceramic. The relevant problems of the upconversion optical thermometryproperties and the upconversion fluorescence intensity of Er3+influenced by the thermaleffect of pumping laser have been studied based on Er3+/Yb3+codoped Y2O3nanocrystals and Er3+/Yb3+codoped Y2O3ceramic.The fluorescence thermometry properties of Er3+/Yb3+codoped Y2O3nanocrystalsand Er3+/Yb3+codoped Y2O3ceramic have been studied. A series of Er3+/Yb3+codopedY2O3nanocrystals of different Yb3+doping concentrations were prepared by the sol-gelmethod. X-ray diffraction was used to characterize the sample. Excited by a980nm LDlaser, The upconversion fluorescence spectrum of Er3+/Yb3+codoped Y2O3nanocrystalshas been studied. It has been found that the sample has the high fluorescence efficiencyand the obvious thermal effect when the doping concentration was1mol%Er3+/10mol%Yb3+. The upconversion fluorescence spectrum of this sample was measured atdifferent temperature from323-773K, the green fluorescence thermometry propertieshave been analysized based on Er3+/Yb3+codoped Y2O3nanocrystals, It was found thatwhen the temperature was623K, The highest thermometry sensitivity of the systemwas obtained, about5.1x10-3K-1. At the same time, according to the boltzmanndistribution law, the number of particles on the splitting energy levels of Er3+:4S3/2and2H11/2was analyzed along with the change of temperature,and the correctness of thetheory was verified by the experiment. Calcined the Er3+/Yb3+codoped Y2O3nanocrystals to Er3+/Yb3+codoped Y2O3ceramic through high temperature, theupconversion fluorescence spectrum was measured at the low temperature, it has beenfound that when the temperature was lower than0℃, there is a big rasidual inmeasuring the temperature based on the fluorescence intensity ratio.The upconversion fluorescence intensity of Er3+influenced by the thermal effect ofpumping laser was studied. The upconversion fluorescence intensity was measured atdifferent pumping power, by making a comprehensive analysis about the fluorescenceintensity with different pumping power and the fluorescence intensity with differentmeasurement temperature, it is concluded that the relationship between the pumping power and the temperature of the sample light spot. It has been found that thetemperature of the light spot rise rapidly with the increasing of pumping power, whenthe pumping power is770mW, the surface temperature of the sample rised to643.5K.The excited states nonradiation relaxation rate of rare earth increased caused by the hightemperature, and then it quenched the rare earth fluorescence, which played a key rolein the fluorescence intensity saturation phenomenon. According to the thermal couplingtheory and the log-log graph of564nm, we got the log-log graph of540nm and524nm.It has been obtained that N1(the corresponding energy of564nm) and N3(thecorresponding energy of524nm) are thermal coupling levels, N1and N2(thecorresponding energy of540nm) are thermal coupling levels through the comparison oftheoretical and experimental double logarithmic curve. The degree of the thermalcoupling of N1and N2is better than those of N1and N3’s. |
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