Photoluminescenc Of Niobate Salts Doped With Rare-earth Ions And Its Temperature Sensing Applications

Temperature is a physical quantity that characterizes how hot or cold an object is.Accurate temperature measurement is crucial in the fields of aerospace,defense,climate research and medicine.The optical thermometer is a new type of non-contact thermometer,which measures temperature based on the characteristics of the phosphor's luminous intensity,spectral position,and excited state lifetime.This type of thermometer has high sensitivity(?1%K-1),high spatial resolution(?10 ?m)and fast response time(?1 ms).In addition,the optical thermometer can also work under the electric field,and the thermocouple thermometer is greatly affected by the electric field.The work of this thesis focuses on the luminescence characteristics of several rare earth ion-doped niobate.It mainly includes three parts:the first part is the temperature detection using the fluorescence intensity ratio in the two rare earth ion co-doped yttrium niobate materials;the second part is a rare earth ion-doped lanthanum niobate,which uses the ground-state thermal coupling method for temperature detection;the third part is about the single-matrix white light.The first chapter mainly introduces the research status of luminescent materials,the application of rare earth luminescent materials,various optical temperature measurement methods,the commonly used characterization methods of luminescent materials,the theory of rare earth spectroscopy,and explains the temperature quenching phenomenon according to the configuration coordinate model.The second chapter mainly introduces the luminescence characteristics of YNbO4:Eu3+,Er3+and the temperature dependence of the sample luminescence.First,we use the excitation light of 487.6 nm to excite the Eu3+ions to excite the Eu3+ ions that populated in the 7F2 state to the high-energy excited state 5D2.After being excited to the SD2 state,the Eu3+ion will quickly relax to the SD0 state.At this time,we can monitor all the emissions from 5D0 to 7FJ.The integration range we selected in the experiment is 580 im to 630 nm,covering 5D0 to 7F1 and 7F2,and these emissions accounted for more than 80%of the emission intensity.The co-doped Er3+ion is used as a reference.The selective excitation wavelength of Eu3+ ion can just excite Er3+ ion from the ground state at the same time,so the emission intensity of Er3+ion can be guaranteed.According to the fitting result of the fluorescence intensity ratio,the effective energy difference is 574 cm"1,the relative sensitivity reaches the maximum value of 2.9%K-1 at 137 K,and the temperature resolution is as low as 0.03 K.The above results indicate that YNbO4:0.02 Eu3+,0.005 Er3+materials have great potential in the field of temperature detection.In the experiment,the sample was first synthesized by high temperature solid phase method,and the structure was characterized by X-ray diffraction spectrum.It was found that the crystal phase was good and the sample was successfully synthesized.Then monitor its excitation spectrum and emission spectrum to study its luminescence characteristics.However,the energy difference between the energy levels of Eu3+ ions 7F0 and 7F2 is not large,making the relative sensitivity of the temperature measuring material not high enough.In Chapter 3,we try to use Pr3+ion as the luminescence center(the energy difference between the ground state level 3H4 of Pr3+ion and the excited state 3H5 is about 2000 cm-1,which will correspond to a greater sensitivity).We performed concentration optimization results using a 2%doped concentration sample and monitored its emission spectrum with a 450 nm pulsed laser excitation,the emission of 3P1 and 3P0,the pair of thermally coupled energy levels,at 532 nm and 558 nm,exhibit typical temperature changes with temperature,so the fluorescence intensity ratio of these two groups of emission is selected to study the temperature detection.In the temperature measurement range of 243 K to 483 K,243 K corresponds to the highest relative sensitivity of 1.2%K"1,and 300 K corresponds to the relative sensitivity of 0.8%K-1.We also use the thermal coupling between the ground state 3H4 of the Pr3+ion and the excited state 3H5 to excite the Pr3+ ion that resides in the 3H5 energy state.As the temperature increases,the number of Pr3+ions in the 3H5 energy state increases,and the luminous intensity also increases.Temperature detection is performed using the property of monotonous change of luminous intensity with temperature.Under the excitation of 532.2 nm,the emission of Pr3+ions at 652 nm increases with increasing temperature.In order to compensate for the impact of temperature quenching,the quenching coefficient under the excitation at 450 nm was selected and corrected.At 243 K,the relative sensitivity reaches 3.2%K-1,which is higher than the result obtained by the thermal coupling of the excited state before.In Chapter 4,we studied single matrix white light.We chose ZnB2O4 as the matrix,doped with Bi3+ions and Eu3+ions.Under the excitation light of 380 nm near ultraviolet wavelength,the emission peak of Bi3+ is located at 487 nm,and the half-height width is 100 nm.Because the doping concentration of Bi3+ ions is 10%,the intensity of the emitted light is the strongest.Subsequent experiments are conducted on the basis of this concentration.The red light emission intensity of Eu3+ions is relatively high,so when the concentration of Eu3+ions is increased,the luminescence of the sample changes from blue to white.In addition,combined with the excitation spectrum of Eu3+ ions,we found that there is energy transfer from Bi3+ions to Eu3+ ions during the luminescence process.Under the final excitation at 380 nm near ultraviolet light,ZnB2O4:0.1Bi3+,0.04Eu3+,0.14Li+,the color coordinate of the emitted light is(0.3615,0.3476),and the color temperature is 3648 K.