| Our group has fabricated zirconia fibers successfully.In the dissertation,according to fluorescence intensity ratio technology based on thermal coupling level of rare earth ions,the temperature sensing properties of zirconia luminescent fibers were explored;energy transformation and crystal structure optimization of host were adopted to explore the approaches to enhance fluorescence intensity and luminescent efficiency of ZrO2 luminescent fiber cloth and LaNiTiO6 phosphors.The main contents of the thesis are as bellow:1.Temperature sensing properties of ZrO2:RE3+(RE=Er3+,Ho3+/Yb3+)fibresZrO2,as one famous thermal insulation material,has many other natures,such as excellent thermal stability,resistance of chemical corrosion,antioxidant,non-volatile,non-toxic,non-polluting,as well as low phonon energy,making ZrO2 can served as one host material in up-conversion fluorescent materials.(1)ZrO2:0.2 mol%Er3+ and ZrO2:0.5 mol%Ho3+,10 mol%Yb3+ precursor spinning solution was synthesised by sol-gel method.The precursor fibers were obtained via electrospinning technique.Ultimate fibers could be achieved after undergoing heat treatment process.The crystalline structure and morphology were analyzed,and ZrO2:0.5 mol%Ho3+,10 mol%Yb3+ fibres display tetragonal,and the diameter of the fibers is about 1?1.5 ?m.(2)The dependences of temperature and up-conversion emission spectra were studied according to temperature detection principle of fluorescence intensity ratio based on thermal coupling level of rare earth ions.The thermal coupling levels of Er3+are 2H11/2 and 4S3/2,and the energy gap is about 700?800cm-1.Under 980 nm excitation,we analyzed the dependence relationship between temperature(T= 10?531 K)and the ratio of fluorescence intensity radiated by the two thermal coupling levels 2H11/2 and 4S3/2 of Er3+ in ZrO2:0.2 mol%Er3+ fibres,and calculated the absolute sensitivity(SA)and relative sensitivity(SR).It is found that in the scope of 300?531 K,its SR is higher compared with the other researched temperature sensing materials.At 70 K,SR is 17%· K-1.The relative sensitivity decreases with the temperature increasing.SR is 1.45%· K-1 and 0.51%· K-1 at room temperature and 500 K,respectively.So high sensitivity means it has significant value in the field of non-contact fluorescence temperature sensing.(3)Enhance the optimal detecting scope of temperature by selecting suitable doped ions according to the thermal coupling level gaps.The thermal coupling levels of Ho3+ are 5F1/5G6 and 5F2,3/3K8.Owing to the energy level difference is bigger relatively,at a lower temperature,the population of Ho3+ ions is less relatively,leading the fluorescence intensity of up level is too weak to be applicable to temperature sensing.Therefore,a series of temperature related up-conversion emission spectra of ZrO2:0.5 mol%Ho3+,10 mol%Yb3+ fibres were measured from 300 to 650 K.The dependence relationship between temperature and the ratio of fluorescence intensity radiated by the thermal coupling levels of Ho3+ were analyzed,and its SA and SR were also calculated.At 360 K,SR is 0.61%· K-1,being up to maximum.When T is 300 K and 500 K,SR are 0.56%· K-1 and 0.53%· K-1,respectively.Although its relative sensitivity is small,the changes of fluorescence intensity ratio is very obvious,having great reference value in researching the temperature sensing of Ho3+ doped fluorescence materials.2.Up-conversion fluorescence enhancement and wavelength adjustment caused by co-doped of Yb3+ in ZrO2:Er3+ fiber clothZrO2:x Er3+ fibers have excellent temperature sensing properties,and its SR is high.In order to enhance its fluorescence intensity,the detailed parameters in Er3+doped Zr02 fibers were regulated and controlled.The fluorescence intensity was enhanced by adding sensitizer Yb3+ ions,and it is found that the color of emitting light could be adjusted by changing the doped concentration of Yb3+.(1)ZrO2:x Er3+,y Yb3+ fiber cloth was synthesised by the above method.From XRD patterns,it could be found that the crystalline structure of ZrO2:x Er3+,y Yb3+fiber cloth transform from monoclinic to tetragonal with the doped concentration of Yb3+ increasing.(2)Fluorescence intensity was enhanced by introducing sensitizer Yb3+.Up-conversion emission spectra of ZrO2:x Er3+,y Yb3+ fibre cloth were measured at room temperature.It could be found that co-doped of Yb3+ ions could enhance the fluorescence intensity of ZrO2:x Er3+ fibers remarkably.By means of analyzing the up-conversion luminescence mechanism,given Yb3+ has large absorption cross section to 980 nm light,Yb3+ could transfer energy to adjacent excited Er3+ ions under 980 nm excitation,increasing the population of Er3+ ions located at excited state and the probability of radiative transition of Er3+,enhancing the fluorescence intensity.(3)Adjust the wavelength of emitting light by adjusting the doped concentration of activator/sensitizer.The ratio of red light and green light emission intensity of ZrO2:x Er3+ fibers gradually increases with the doped concentration of Yb3+ ions increasing.When the doped concentration of Er3+/Yb3+ is up to the critical value,concentration quenching may occurs.It could decrease fluorescence intensity and fluorescence lifetime,while the emission intensity is still higher than that of Er3+ single doped sample.At the same time,the cross relaxation in Er3+-Er3+ or Er3+-Yb3+ could promote red light emission,weak green light emission,making the ratio of red/green bigger and bigger.When the doped concentration of Yb3+ ions is 0 mol%,ZrO2:0.2 Er3+fibers emitted pure green light.When the doped concentration of Yb3+ ions is 5 mol%,ZrO2:0.2 Er3+,5 mol%Yb3+ fibers emitted yellow light generated by combination of red and green light.When the doped concentration of Yb3+ ions is 20 mol%,ZrO2:0.2 Er3+,20 mol%Yb3+ fibers emitted pure red light.So,according to need,specific light emission could achieve by means of adjusting the doped concentration of Er3+/Yb3+,realizing wavelength adjustment(from green,to yellow,to red),which has potential value in the field of requiring high emitting strength and special wavelength optical signal output.3.Fluorescence enhancement caused by Bi3+/Li+ in LaNbTiO6:Ho3+ and LaNbTiO6:Er3+ phosphorsLaNbTiO6 possesses good thermal,physical and chemical properties,and it has been studied in ferroelectric,piezoelectric,microwave medium and photocatalysis.In fact,LaNbTiO6 is a excellent photoactive host materials owing to its relatively complicated crystal structure and strong crystal field.(1)LaNbTiO6:Ho3+,y Bi3+ and LaNbTiO6 x Er3+,y Li+ phosphors were synthesized by so-gel-combustion method,and heat treatment process.From XRD patterns,all the doped samples display orthorhombic phase.La3+/Ho3+/Bi3+/Er3+located at the center of eight Nb/Ti-O octahedron,while Li+ with small size located at interstitial position of LaNbTiO6.(2)Fluorescence spectra of LaNbTi06:x Ho3+,y Bi3+ samples were measured.It is found that emission spectrum of Bi3+ ions single doped LaNbTiO6 sample has large overlap with excitation spectrum of Ho3+ ions single doped LaNbTO6 sample.As a result,in LaNbTiO6:x Ho3+,y Bi3+,Ho3+ could absorb partial emission light energy of Bi3+ ions,adding the excitation source of Ho3+ ions,promoting the characteristic emission of Ho3+ ions,enhancing the fluorescence intensity of LaNbTiO6:x Ho3+.Given the advantages of physical and chemical stability,innocuous and environmental of LaNbTiO6:4 mol%Ho3+,2 mol%Bi3+ phosphors could serve as one kind of pure green phosphors with high emitting strength and high efficiency,which has good reference significance in trichromatic phosphors.(3)Co-doping of Li+ in LaNbTiO6:Er3+,Li+ samples enhances the fluorescence intensity of Er3+ remarkably.As to LaNbTiO6:Er3+ sample,its diffraction peak position occurs red shift to some extent compared with pure LaNbTiO6 sample,while the co-doping of Li+ in LaNbTiO6:Er3+ samples making the diffraction peak occurs blue shift to some extent,making XRD patterns of LaNbTiO6:Er3+,Li+ and LaNbTi06 complete overlapped.That is to say,the introduction and charge compensation of a certain amount Li+ could improve crystalline structure of LaNbTiO6:Er3+ samples and the symmetry of crystal field around Er3+ ions,relief fluorescence quenching phenomenon generated by excess Er3+ ions doped,realizing fluorescence enhancement of Er3+.In this dissertation,on the basis of ZrO2 fibers fabricating successfully,optical temperature sensing materials?Er3+/Ho3+/Yb3+ doped ZrO2 fibres were synthesised.In the scope of 300?600 K,the relative sensitivity of ZrO2:0.2 mol%Er3+ fibres is up to 1.45%·K-1'.In order to satisfy the demands of high fluorescence intensity and high luminescence efficiency in rare earth luminescent material,Yb3+/Bi3+/Li+ ions were doped in ZrO2:x Er3+ fibre cloth and LaNbTiO6:x Ho3+/Er3+ phosphors.It certified that the co-doping of Yb3+/Bi3+/Li+ could enhance fluorescence intensity and luminous efficiency remarkably by adding sensitizer,energy transformation,crystal structure optimization of host.The luminescence mechanism were also be studied in detail.The research results will provide approaches and bases for broadening the measurement range of temperature,enhancing sensitivity,realizing the development of fluorescence materials with high emission intensity and efficiency. |
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