Structure and Stability of Europium Doped B-Alumina Type Phosphor

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dc.contributor.advisorCormack, Alastair
dc.contributor.authorWu, Zhehua
dc.date.accessioned2017-02-07T15:26:13Z
dc.date.available2017-02-07T15:26:13Z
dc.date.issued2002-07
dc.descriptionAdvisory committee members: Paul Johnson, Doreen Edwards, Robert Condrate. Dissertation completed in partial fulfillment of the requirements for the degree of Doctorate of Philosophy in Ceramics at the Kazuo Inamori School of Engineering, New York State College of Ceramics at Alfred Universityen_US
dc.description.abstractBaMgAl10O17 (BAM) has been widely used as the host material for Eu-active phosphors for lamps and display panels. It has a luminescent wavelength ranging from 430nm to 450nm, blue in color. However, there is a degradation problem for this phosphor material: the luminescent intensity decreases and the emission band shifts from blue toward green in color with an increase in application period and annealing procedure of manufacture. The suggestion that the luminescent degradation is related to the oxidation of europium from a 2+ to 3+ oxidation state forms the basis for the first part of this thesis. A computer simulation study of the behavior of europium in BAM (based on the classical Born model description the ionic materials) was carried out. Europium ions were found to prefer different lattice positions depending on their valence state: Eu2+ prefers the BR site in the mirror plane; Eu3+ prefers the Al(2) site in the spinel block. Because there are many other barium hexa-aluminate phases besides BAM and because they can also be used as the phosphor host materials, the phase relationship between these phases and the properties of the Eu dopant in these phases were also investigated, in particular, for the barium-poor phase, Ba0.75Al11O17.25. The barium-poor phase, after doping with Eu2+, shows a broader and shifted emission band compared to BAM. The formation of barium-poor phase has also been proposed as the reason for the observed luminescent degradation in BAM. Calculations on the barium-poor phase were performed to investigate the origin of the emission band differences between it and BAM, and the complete solid solution between them. The coexistence of multiple OBR-distributions in the barium-poor phase was found to be the origin of the observed broader and shifted emission band of Eu2+. Since the hypotheses about luminescent degradation involve phase changes or structural adjustments, molecular dynamics simulations of ion migration were also performed to study the defect and structural changes after the europium oxidation. It was found that Eu3+ ions can migrate from the mirror plane to the spinel block at relatively low temperature, and that Eu2+ ions have a tendency to congregate in BAM.en_US
dc.description.sponsorshipU.S. Department of Energyen_US
dc.format.extent137 pagesen_US
dc.identifier.urihttp://hdl.handle.net/10829/7385
dc.language.isoen_USen_US
dc.publisherNew York State College of Ceramics at Alfred University. Kazuo Inamori School of Engineering.en_US
dc.relation.ispartofScholes Libraryen_US
dc.rights.urihttps://libraries.alfred.edu/AURA/termsofuseen_US
dc.titleStructure and Stability of Europium Doped B-Alumina Type Phosphoren_US
dc.typeThesisen_US

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