Energy Level Parameters And Optical Transition Properties Of Er³⁺ Doped Phosphors

J-O theory is an effective manner for realizing the optical transition properties of rare earth in transparent hosts such as glasses,transparent ceramics and single crystals.Judd-Ofelt treatment is commonly accepted and widely employed.However,its usage in those systems whose absorption spectra are not possible to be measured was limited.Facing this problem,in this thesis we proposed a calculation route in the framework of transitional Judd-Ofelt to obtain the optical transition properties,and the optical transition properties of two Er3+ doped systems were studied.Er3+ doped laurustinus-shaped NaY(WO4)2 microspheres were prepared using a microwave assisted hydrothermal reaction.X-ray diffraction(XRD),field-emission scanning electron microscope(FE-SEM)and diffuse-reflection spectroscopy(DRS)were conducted to characterize the obtained sample.The XRD pattern indicated that the resultants existed in a body-centered phase,and the FE-SEM images showed that the sample was composed by many laurustinus shaped microspheres.Intrinsic absorption transition peaks of Er3+ were observed in the collaborated DRS(namely the quasi-absorption spectrum),and then the central wavenumbers for Er3+ absorption transitions were confirmed via numerical calculations.Partial energy level parameters of Er3+ in NaY(WO4)2 were derived based Taylor series expansion to be F2= 429.20,F4= 68.18,F6= 7.20,?= 2422.92.Starting from the J-O theory,the optical transition intensity parameters Ot(t=2,4,6)were derived to be 1.73×10-20,0.94×10-20 and 0.57×10-20 cm2,respectively.Furthermore,the oscillator strengths,spontaneous radiative transition rates,radiative lifetimes and branching ratios for some transitions of Er3+ were confirmed.Er3+ doped Lu2O3 phosphor was synthesized through a high temperature solid state method.XRD and FE-SEM were used to characterize the crystal structure and morphology of the obtained sample.It was found that the received power was cubic-phased Lu2O3 as expected,meanwhile the grain size of the phosphor was nonuniform,and the morphology of the particles was irregular.Particles with small size were aggregated together to form a grain with large size.In an analogical way,the central wavenumbers were derived from DRS,and some energy level parameters of Er3+ in Lu2O3 were confirmed based on the Taylor series expansion technique to be F2= 432.49,F4= 68.04,F6= 7.45 and ?=2401.10.Similarly,the Judd-Ofelt parameters of Er3+ in Lu2O3 were also confirmed by using the DRS data to be Q2= 0.35×10-20,?4=0.74×10-20 and ?6= 0.43×10-20 cm2.In addition,the radiative transition rates,fluorescence branching ratios and radiative lifetimes were also calculated by using the obtained Judd-Ofelt parameters.