Disorder and Diffusion in Mayenite

• Authors: H. Boysen , I. Kaiser-Bischoff , M. Lerch , S. Berendts , M. Hoelzel , A. Senyshyn
• Languages of publication: EN

Abstracts

EN

Mayenite, Ca_{12}Al_{14}O_{33}, has attracted enormous attention for novel technological applications after the discovery of its high oxygen ionic conductivity. The crystal structure consists of a calcium-aluminate framework, comprising 32 of the 33 oxygen anions. The remaining oxygen is distributed over 1/6 of large cages within the framework. The true structure is heavily disordered and usually non-stoichiometric due to the presence of extra anions and is presented for four samples: pure oxygen mayenite (O-mayenite), partly (O/N-mayenite) and fully (N-mayenite) exchanged by nitrogen and doped with iron (Fe-mayenite). All samples were investigated by neutron powder diffraction up to 1050°C. Data were analysed by the Rietveld method and by difference Fourier methods. As prepared O-mayenite contains O_{2}^{-} and OH^{-}, N- and O/N-mayenite also NH_{2}^{-}, NH^{2-} and N^{3-}, while Fe-mayenite was free of extra radicals. In O- and N-mayenite the extra species are lost under vacuum conditions above ca. 700°C, whereas O/N-mayenite retained NH_{2}^{-} up to high temperatures. Diffusion of oxygen proceeds via a jump-like interstitialcy process involving exchange of the "free" oxygen with framework oxygen, coupled to relaxations of Ca ions. In O/N-mayenite NH_{2}^{-} diffuses via interstitial process. In Fe-mayenite encaged oxygen is "invisible" due to extreme delocalisation or loss.

Keywords

EN

61.43.-j; 61.66.-f; 61.05.fm

Discipline

• 61.43.-j: Disordered solids(see also 81.05.Gc Amorphous semiconductors, 81.05.Kf Glasses, and 81.05.Rm Porous materials; granular materials in materials science; for photoluminescence of disordered solids, see 78.55.Mb and 78.55.Qr)
• 61.66.-f: Structure of specific crystalline solids(for surface structure, see 68.35.B-)
• 61.05.fm: Neutron diffraction

• Publisher: Institute of Physics, Polish Academy of Sciences
• Journal: Acta Physica Polonica A
• Year: 2010
• Volume: 117
• Issue: 1
• Pages: 38-41

Dates

published

2010-01

Contributors

author

H. Boysen

• Department für Geo- und Umweltwissenschaften, Sektion Kristallographie, LMU München, Am Coulombwall 1, 85748 Garching, Germany

author

I. Kaiser-Bischoff

• Department für Geo- und Umweltwissenschaften, Sektion Kristallographie, LMU München, Am Coulombwall 1, 85748 Garching, Germany

author

M. Lerch

• Institut für Chemie, TU Berlin, Str. des 17. Juni 135, 10623 Berlin, Germany

author

S. Berendts

• Institut für Chemie, TU Berlin, Str. des 17. Juni 135, 10623 Berlin, Germany

author

M. Hoelzel

• TU Darmstadt, Institute of Materials Science, Petersenstr. 23, 64287 Darmstadt, Germany

author

A. Senyshyn

• TU Darmstadt, Institute of Materials Science, Petersenstr. 23, 64287 Darmstadt, Germany

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Identifiers

DOI

10.12693/APhysPolA.117.38