| There is inextricably correlation between the luminescence research and other subjects,such as the discoveries of cathode rays,radioactivity,and X-rays.Therefore,it is also a benefit to the development of luminescence and other subjects.In recent years,the researches rare earth have made a lot of progress,which lead to the developments of the cross discipline between the luminescence,bo agriculture,animal husbandry and medicine.We have studied the luminescence properties(intensity,luminescence wavelength and long afterglow)of some silicon-based/alumina-based oxide phosphors,which plays a significant role in luminescence research.This paper was divided into eight chapters:Chapter 1 is the introduction,which mainly introduced the research progress of rare-earth luminescent materials.Meanwhile,the professional terms and typical synthesis methods commonly used in phosphor were described.In addition,this chapter briefly introduced the writing ideas and content of this paper.Chapter 2 briefly explains the experimental instruments.The application methods and common problems were introduced in this chapter.We also introduced calculation software used in the calculation.Chapter 3 introduced the effect of reducing oxygen vacancies on the Ce and Tb co-doping in(Ca1-xSrx)7(SiO3)6Cl2 phosphors.Firstly,we successfully synthesized this phosphor by the solid state reaction method.The energy transfer between Ce3+,Tb3+and the transformation from blue light and green light were studied.According to the function of energy transfer.The energy transfer from Ce3+to Tb3+was controlled by a dipole-dipole interaction mechanism,and the largest energy transfer efficiency was more than 96.2%in(Ca1-xSrx)7(SiO3)6Cl2.At the same time,Ce and Tb co-doping can reduce oxygen vacancies,which generated by doping of Ce.This caused the luminescence intensity increased of Ce in(Ca1-xSrx)7(SiO3)6Cl2.Trivalent cations of small radius and Ce co-doping further demonstrated the experiment results.Chapter 4 reported the optimum synthesizing conditions of ?-Sr2SiO4:Eu phosphor.The efficient luminescence wavelength was changed by Ca,S doping.The experimental results showed that pure ?-Sr2SiO4:Eu can be synthesized in N2 atmosphere at 1200?.When Ca was doping,the range of light absorption increased.The spilt of crystal field caused the variation of energy level and the red shift of emission spectrum.The calculation results further detemined that the energy gap decreased after Ca doping,which also caused the red shift of the luminescence.Because of the radius of S is larger than O,the size of the space around Eu was larger when O replacing in ?-Sr2SiO4:Eu by S.So that,the Sr(?)was more likely replaced to give priority to Eu.Meanwhile,the formation energy of Sr(?)is much lower than that Sr(?).The probability of occupation in Sr(?)is increased and the emission of blue light is also increased.Chapter 5 told a story about the europium reduction in G-La2Si2O7.AlF3 promoted the phase formation,more importantly,it promoted the reduction of Eu3+ to Eu2+.The results of Eu L3-edge XANES characterization showed that only Eu3+can be detected in as-received G-La2Si2O7 phosphor and that Al2O3 addition leads to a partial reduction of Eu3+ to Eu2+,while complete reduction occurs with AlF3 addition.The analysis of Fourier transform infrared spectroscopy(FT-IR)and 27Al nuclear magnetic resonance(NMR)results suggests that Al occupies the Si sites and F occupies the O sites.The positive influence of Al-F doping is linked to the structure of the produced phosphors,which was analyzed with the aid of first-principles density functional calculations.Fluorine is actively involved in the system,since the oxygen vacancy is strongly prone to provide electrical charge in order to reduce Eu3+to Eu2+.Chapter 6,we turned on and off the long afterglow property of SrAl2O4:Eu through different ion doping.It found that the long afterglow properties of SrAl2O4:Eu significantly improved by substitution of B atom,while the long afterglow property reduced by doping of F atom.The B doping produced oxygen vacancies.The outstanding long afterglow luminescent is mainly tailoring of the defect level by oxygen vacancies.We detected the presence of oxygen vacancies by means of EPR and XPS.DFT calculation results showed that the partial density states(PDOS)of Eu 5d decreased via boron co-doping.The effect of the prescence of oxygen vacancy energy level increased the long afterglow performance.The emission intensity decreased with the decreasing of Eu 5d state density.The doping of F eliminated oxygen vacancies defects and increased PDOS of Eu 5d.Thus,its long afterglow property turned off and the luminescence intensity increased.Chapter 7 tried to control the synthesis conditions to realize the change of luminescence after thermal decomposition of vinyl polysilazane,and finally realized the enhancement of luminescence through the change of sintering temperature or atmosphere.The optimized sintering temperature was 600? and the atmosphere was ammonia in 60min.Chapter 8 is a summary of the whole text,and gives the deficiencies and the parts that can be further studied in the future. |
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