Luorescence Properties And Optical Thermometry Of Manganese-doped Alkaline Earth Aluminates And Their Complex Phosphors

Non-contact temperature sensor has become a research hotspot in this field because of its fast response speed,high spatial resolution and remote temperature measurement.Due to its own limitations,traditional thermometers are difficult to achieve fast and accurate measurements in the nano/micro-nano space.The fluorescence intensity ratio thermometry solution has become the preferred solution because of its advantages of self-calibration and not being affected by the excitation light source.This paper includes three systems works.（1）A series of Zn Al₂O₄/CaAl₁₂O₁₉:Mn⁴⁺,ln(Tb³⁺,Eu³⁺,Pr³⁺),x Zn Al₂O₄/CaAl₁₂O₁₉:Mn⁴⁺,red phosphors were prepared by high temperature solid-phase method.The results of XRD structure refinement show that the dual-phase red phosphors with different substance ratios were successfully synthesized.The effects of H₃BO₃ addition,Zn Al₂O₄ doping,Mn⁴⁺ion doping concentration and co-doped rare earth ions on the luminescence properties of CaAl₁₂O₁₉:Mn⁴⁺were analyzed by fluorescence spectroscopy.When the amount of H₃BO₃ is 5wt%,the ratio of Zn Al₂O₄ to CaAl₁₂O₁₉ is 1:1,and the doping concentration of Mn⁴⁺is 0.04,the luminescence intensity of the CaAl₁₂O₁₉:Mn⁴⁺sample is the highest.At the same time,doping Zn Al₂O₄ also has a positive effect on improving the quantum efficiency of CaAl₁₂O₁₉:Mn⁴⁺;co-doped rare earth ions(Tb³⁺,Eu³⁺,Pr³⁺)are beneficial to improve the luminescence intensity of the Zn Al₂O₄/CaAl₁₂O₁₉:0.04Mn⁴⁺sample,but due to the difference in the energy levels of different rare earth ions,the luminescence enhancement effect is different,and the enhancement effect of co-doped Eu³⁺ions is the most good.The Zn Al₂O₄/CaAl₁₂O₁₉:0.04Mn⁴⁺phosphor can be used for thermometry applications in the temperature range of 298～418 K.The value of S_a was 4.32×10^-3 K^-1,and the maximum S_r was 3.65×10^-3 K^-1.（2）A series of CaAl₁₂O₁₉:Mn⁴⁺,ln(ln=Na⁺,Mg²⁺,Sr²⁺),x Mg Al₂O₄/CaAl₁₂O₁₉:Mn⁴⁺red phosphors were prepared by sol-gel method.The formation energies of Mn²⁺and Mn⁴⁺in Mg Al₂O₄ and CaAl₁₂O₁₉ matrices were calculated respectively.Combined with fluorescence spectrum analysis,the occupied positions of Mn⁴⁺in Mg Al₂O₄/CaAl₁₂O₁₉ matrices were investigated experimentally.The calculated results were consistent with the experimental phenomenon.The results of fluorescence spectrum analysis showed that the doping concentration of Mn⁴⁺ions,the amount of C₆H₈O₇·H₂O,the annealing temperature and the doping amount of Mg Al₂O₄ all affect the luminous efficiency of CaAl₁₂O₁₉:Mn⁴⁺.When the doping concentration of Mn⁴⁺ions is greater than 0.04,the fluorescence quenching will be caused by the increase of the electric dipole-electric dipole（d-d）interaction between Mn⁴⁺.The luminescence intensity of the sample is the strongest when the ratio of C₆H₈O₇·H₂O to metal ions is 2:1.The application of3Mg Al₂O₄/CaAl₁₂O₁₉:0.04Mn⁴⁺phosphor in temperature sensing was studied,and the absolute sensitivity was 4.54×10^-3 K^-1 in the temperature range of 303～418 K;at 438 K,the maximum relative sensitivity was 3.81×10^-3 K^-1.（3）Mg Al₂O₄:Mn²⁺,Na⁺、Mg Al₂O_4-x/2F_x:Mn²⁺、Mg Al₂O_3.5F:y Mn²⁺and Mg Al₂O_3.5F:Mn²⁺,ln(ln=Tb³⁺,Pr³⁺,Eu³⁺,Si⁴⁺)phosphors were synthesized by high temperature solid-phase method.With the increase of Na⁺addition,the ratio variation of the red/green light of the sample can be changed,and the relative excess of Mg O can also adjust the ratio variation of the red/green light.When n_{（Mg F2）}/n_{（Mg O）}is 1,the green emission of Mn²⁺is the strongest.Due to the energy transfer between Pr³⁺and Mn²⁺ions,the luminous efficiency of Mg Al₂O₄:Mn²⁺,Pr³⁺samples is improved.In the temperature range of 318～438 K,the Mg Al_1.8O₄:Mn,0.2Na⁺samples were investigated for temperature sensing applications.Relative sensitivity is positively correlated with temperature,and when the temperature was 438 K,the maximum sensitivity was 3.78×10^-3 K^-1.In summary,we use different means to improve the luminous intensity of phosphors,and at the same time,the quantum efficiency has also been greatly improved.That will effectively improve response signal in optical temperature sensing applications.