Journal Article

PreJuSER-56074

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png The hydrogen economy: technology, logistics and economics

Birnbaum, U.FZJ* ; Hake, J.-F.FZJ* ; Linssen, J.FZJ* ; Walbeck, M.FZJ*

2006
Maney London

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Please use a persistent id in citations: doi:10.1179/174892406X177266

Abstract: The synthetic vanadinites (Pb(x)Ca(10-x))(VO4)6F2delta, 1 < x < 9, adopt a P6(3)/m apatite structure with 9.7590 (1) < or = a < or = 10.1179 (1) A and 7.0434 (3) < or = c < or = 7.4021 (1) A. The partitioning of calcium and lead over the AI(4f) and AII(6h) positions is nonstoichiometric with lead preferentially entering the larger AII site. High-resolution electron microscopy showed that samples annealed for 10 h at 1073 K are in disequilibrium with calcium- and lead-rich microdomains co-existing at unit-cell scales. For (Pb5Ca5)(VO4)6F2delta, sintering in excess of 2 weeks is required for the metals to order macroscopically. As annealing progresses, c/a, the partitioning coefficient kPb(AI/AII) and the AIO6 metaprism twist angle (phi) adjust cooperatively to enlarge the apatite channel, and thereby accommodate higher lead content. These results demonstrate that phi is a sensitive measure of disequilibrium and a useful device for monitoring changes in apatite topology as a function of composition.

Note: Record converted from VDB: 12.11.2012

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Contributing Institute(s):

1. Programmgruppe Systemforschung und Technologische Entwicklung (STE)

Research Program(s):

1. Nachhaltige Entwicklung und Technik (P26)

Appears in the scientific report 2006
Notes: Nachtrag

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