Li ~ to enhance the fluorescence of rare earth ions and mechanisms of the phenomenon

Title: Li ~ to enhance the fluorescence of rare earth ions and mechanisms of the phenomenonAuthor: Bai YunfengDegree-granting unit: Harbin Institute of TechnologyKeywords: conversion;; photoluminescence;; nanocrystals;; multi-phonon relaxation;; Local StructureSummary:

Rare earth ions with a stable chemical properties in the UV - visible - infrared range has a wealth of energy levels, and these levels have a long level lifetime, so rare earth ions is very suitable as upconversion materials. In recent years, a large number of articles reported the rare earth ion doped materials, upconversion luminescence, fluorescence generation mechanism and Neodymium Magnets potential applications. Rare-earth ion doped materials, upconversion luminescence phenomenon has great application value, can be applied in many ways: a small solid-state lasers, information processing, optical storage, color display, 3D display, temperature measurement and bio-fluorescence identification and so on. This thesis study Li ~ co-doped with rare-earth ion oxide Nanocrystals and room temperature upconversion luminescence phenomenon. We found that the incorporation of Li ~, the rare earth ion upconversion luminescence intensity is greatly enhanced, and the fluorescence enhancement mechanism were studied. Thesis research content and results are as follows:

Were prepared by sol-gel Er ~ (3)-doped ZnO, Li ~ / Er ~ (3) co-doped ZnO, Li ~ / Er ~ (3) / Yb ~ (3) co-doped ZnO nano-crystalline materials. Laser excitation at 976nm observed Er ~ (3) ions on the conversion of light hair, and found that after the incorporation of Li ~, Er ~ (3) of the upconversion luminescence intensity greatly enhanced (up to 50 times more powerful). Proposed is a good Li ~ Er ~ (3) ion fluorescence enhancer. Then he studied the Li ~ for other rare-earth ion fluorescence enhancement phenomenon, found in Li ~ mixed, various upconversion luminescence of rare earth ions have a larger intensity enhancement. This is a good Li ~ made of rare earth ion fluorescence enhancer.

Visible emission of rare earth ions for the transition between the 4f electrons caused by the transition probabilities between the 4f electrons of rare earth ions by which the local crystal field effects, the greater the asymmetry of the local crystal field, 4f electron transition probability between the greater. To study the incorporation of Li ~ after the local structure of rare earth ions, we study the X-ray absorption fine Li ~ / Er ~ (3) co-doped ZnO nano-crystalline materials in Li ~ of Er ~ (3) ion local structure, and found that incorporation of Li ~ after Er-O and Er-Er bond length and coordination number changes all that rare-earth ions in which the local crystal field asymmetry increases, so the transition between the 4f electrons increased risk. In subsequent experiments, the application of http://www.everbeenmagnet.com/en/products/110-sintered-neodymium-magnets JO theory analysis of Li ~ Er ~ (3) ion absorption cross section and the radiation coefficient, and found that after the incorporation of Li ~ Er ~ (3) the level of ion absorption coefficient and radiation coefficients increase This is increasing 4f electron transition probability between the visual performance.

Li ~ incorporation of the phonon energy of matrix without any change, but the sample surface defect states (OH ions) dramatically reduced, OH ions have large phonon energy, it can greatly increase the sound level between the multi- sub-relaxation, so the reduction in OH ion energy levels between the multi-phonon relaxation weakened, which is converted on the fluorescence enhancement of one of the reasons.

Of Er ~ (3) doped Y_2O_3 and Li ~ / Er ~ (3) co-doped nanocrystalline materials Y_2O_3 the relationship between the fluorescence intensity changes with temperature. Multi-phonon relaxation rate equation model and the experimental curve fitting showed that Er ~ (3) ions between the neighboring energy levels to multi-phonon relaxation process-based, multi-phonon radiative transitions relative relaxation process can be ignored. After incorporation of Li ~, Er ~ (3) ions between adjacent multi-level phonon relaxation probability decreases, so the conversion fluorescence enhancement.

Prepared by Er ~ (3) / Tm ~ (3) / Yb ~ (3) co-doped phosphor Y_2O_3 white, get a bright white fluorescence, in the incorporation of Li ~, its white light intensity is enhanced; in Li ~ / Er ~ (3) co-doped nanocrystalline materials Y_2O_3 study based on Er ~ (3) fluorescence peaks than ion temperature is proposed which is a very good temperature fluorescent material.Degree Year: 2009