Study On The Luminescent Properties Of Rare Earth Co-doped CaLaAl₃O₇ Phosphor And Vibrational Spectroscopy Of Xylitol

The rare earth elements are used widely as fluorescent (luminescent) materials. CaLaAl₃O₇ have many merits for its crystal structure characteristics. The luminescent characteristics of CaLaAl₃O₇ doped with rare earth ions had been studied in this thesis. In addition, the vibrational spectroscopy (FT-Raman spectra and FT-infrared spectra) of polycrystalline xylitol were measured and analyzed. This result will help us for fast component analysis of xylitol by Raman spectroscopy.The major research contents and the conclusions were as follows:(a) The CaLaAl₃O₇:Dy³⁺ fluorescent materials could be excited effectively by ultraviolet and near ultraviolet (250 nm～500 nm). The emission spectrum with 348 nm excitation gives sharp emission lines at 478 nm, 578 nm and 667 nm. CIE chromaticity coordinates of CaLaAl₃O₇:Dy³⁺ emission with 0.04 Dy³⁺ concentrations indicates its emission spectrum belongs to white light. The fluorescent material is a promising fluorescent material used in white LED. According to the emission spectra of CaLa_1-xAl₃O₇:xDy³⁺(0.01≤x≤0.15), we suggested that the concentration quenching mechanism is the d-d interaction.(b)There are energy transfer from Tb³⁺ to Eu³⁺ in CaLaAl₃O₇:Tb³⁺,Eu³⁺. The red emission at 619 nm corresponding Eu³⁺ ions transitions of 5D0→7F2 is enhanced. CaLa_0.8Al₃O₇:0.1Tb,0.1Eu phosphors were synthesized under reductive atmosphere. The intrinsic emission spectra of Eu²⁺ (d→f transitions, 350⁵00 nm blue light), Tb³⁺ (5D4→7F5 transitions, 546 nm green light), and Eu³⁺ (5D0→7F2 transitions, 619 nm red light) were observed in the phosphor. This indicates that three activators coexist in single matrix. The CaLaAl₃O₇:Tb,Eu phosphors have potential values in lighting field and PDP field.(c)The FT-Raman spectra and FT-infrared spectra of polycrystalline samples of xylitol have been measured and analyzed. The OH stretching vibration is at about 3360 cm^-1. 2898 cm^-1 and 2945 cm^-1 are the symmetric vibration of CH₂. The C-C stretching vibrations are at between 850 cm^-1 to 920 cm^-1. The C-C stretching vibration is at between 1000cm^-1 to 1110cm^-1.