Study Of Three Important Phenomena In Rare-earth Luminescent Material

Rare-earth ions (lanthanide ions) are characterized by the existence of a paritally-filled 4f shell in their electronic configurations. Due to various excellent luminescent capabilities of those ions beyond other ions, they have attracted intensitive studies for decades and are continuing to be research focus nowadays.Rare-earth-ion doped luminescent glasses keep the good nature of common glass, and at the same time, show great excellent luminescent properties of rare-earth ions. Thus, those glasses have been the focus of researches for the past decades. Among them are the long-lasting phosphorescence glasses and upconversion phosphorescence glasses, which have gained extended market prospect and significance in research. Existence practical applications include the communication based on optical-wave guide, the fiber amplifier, the lasers, hydrospace detection, biomedical technology and optical storage materials in the fields such as architecture, environment protection, decoration as well as craftwork. Hence, rare-earth doped luminescent glasses are indispensable materials for people's everyday life, manufacture and scientific research.The introductory chapter presents the aims and significance of the research in general, and then summarises the fundamental theory (the phenomenological crystal-field theory), glass preparation and optical spectroscopy. The main findings of this research work are also summarized at the end of this chapter.Chapter 2 presents in details the glass prepartation processes and the methods of measurement and analysis of optical spectra used in the follwing chapters.Chapter 3 is on the preparation and spectroscopic analysis of Ce³⁺-doped zinc phosphate glasses. It is the work carried out in the beginning of the M.Sc. research work, serving the purposes of getting familiar with preparation of luminescent material and using Ce³⁺ as sensitizer for latter study.Chapter 4 focuses on the energy transfer from Ce³⁺ to Tb³⁺ and Ce³⁺ to Eu³⁺ through specialized spectrum measured and analysis on prepared glass samples.Chapter 5 presents one of the important research results. It focuses on the examination of one of the critical implicit assumptions in a paper published on Phys. Rev. Lett. By preparation and spectroscopic measurement of a series of lead borate glasses, the trends of the variation of the electric dipole line strengths versus glass compositions are obtained for various models. The results indicate that the assumptions do not hold. Chapter 6 presents another important progress on the research work. Based on the simple model for f-d transitions of doped rare-earth ions, the energy level structures 4f-5d transitions are calculeted for the case of strong 5d crystal-field interaction. It has been shown that, under certain approximations, the line strengths of transitions to or from from a series of energy levels with a given 5d crystal-field component are purely determined by group theory, and so are independent of the host lattice. The results have been used to interpret the measured data for Nd³⁺ in various crystals.Finally, the progresses maded in this research work and the perspective on future researches are presented in last chapter.