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Ambi-site substitution of Mn in Lanthanum Germanate Apatites

Kendrick, E and Knight, K.S. and Slater, P.R. (2009) Ambi-site substitution of Mn in Lanthanum Germanate Apatites. Materials Research Bulletin, 44. pp. 1806-1809.

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URL of Published Version: http://www.sciencedirect.com/science/article/pii/S0025540809000944

Identification Number/DOI: DOI: 10.1016/j.materresbull.2009.03.002

A neutron diffraction study at 4K of the Mn doped lanthanum germanate apatite-type oxide ion conductor of nominal starting composition “La9.5Mn0.5(GeO4)6O2.75” is reported. The structure was refined in space group P63/m, although high thermal displacement parameters were observed for the oxide ion sites (particularly O3, and O4). Reduced thermal displacement parameters were obtained by splitting the O3 site, and allowing the O4 oxygen to move off site, which may indicate local regions of lower symmetry within the structure. In addition, the data suggested ambi-site substitution of Mn, with it being present on both the Ge site and the La site. Assuming no change in La:Mn:Ge ratio, a composition of La9.18Mn0.28(GeO4)5.8(MnO4)0.2O2 was determined. As such there are nominally no interstitial oxide ions, but rather cation vacancies on the La site. Therefore, the high conductivity for this sample is most likely related to the introduction of Frenkel-type defects at higher temperature, as previously proposed for other apatite-type systems containing vacancies on the La site

Type of Work:Article
Date:05 August 2009 (Publication)
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:School of Chemistry
Keywords:apatite, solid oxide fuel cells, electrolyte
Subjects:QD Chemistry
Institution:University of Birmingham
Copyright Holders:Elsevier
ID Code:780
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