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Oxygen surface exchange and oxygen chemical diffusion coefficients of LaNi0.4Fe0.6O3-δ ceramics are determined via conductivity relaxation method after stepwise change of temperature in the range of 700–950 ℃ in air and Ar/O2 gas flow at oxygen partial pressures ( pO2) of 4 Pa, 18 Pa, 37 Pa, 47 Pa and 59 Pa. The highest conductivity (about 160 S·cm-1) is found at 950 ℃ in air. No oxygen exchange (δ = 0) below 700 ℃ is observed in the investigated pO2 range. The oxygen exchange coefficients determined in reduction mode are higher than those determined in oxidation mode. This is explained by clusterization of oxygen vacancies on the surface of the sample investigated in oxidation mode. The opposite tendency is found for chemical diffusion coefficients. Unlike surface, the oxygen vacancies of the volume region are probably not clustered and have predetermined the higher oxygen diffusion mobility of the sample treated in oxidation mode.


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Chemical diffusion and oxygen exchange of LaNi0.4Fe0.6O3-δ ceramics

Show Author's information Jianying CHENa,b,e( )Vladimir VASHOOKbDmytro M. TROTScShaorong WANGaUlrich GUTHb,d
Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050, China
Dresden University of Technology, D-01062 Dresden, Germany
Bayerisches Geoinstitut, Universität Bayreuth, D-95440 Bayreuth, Germany
Meinsberg Kurt-Schwabe Research Institute, Kurt-Schwabe-Straße 4, D-04720 Ziegra-Knobelsdorf, Germany
Shanghai Nanotechnology Promotion Center, Shanghai, China

Abstract

Oxygen surface exchange and oxygen chemical diffusion coefficients of LaNi0.4Fe0.6O3-δ ceramics are determined via conductivity relaxation method after stepwise change of temperature in the range of 700–950 ℃ in air and Ar/O2 gas flow at oxygen partial pressures ( pO2) of 4 Pa, 18 Pa, 37 Pa, 47 Pa and 59 Pa. The highest conductivity (about 160 S·cm-1) is found at 950 ℃ in air. No oxygen exchange (δ = 0) below 700 ℃ is observed in the investigated pO2 range. The oxygen exchange coefficients determined in reduction mode are higher than those determined in oxidation mode. This is explained by clusterization of oxygen vacancies on the surface of the sample investigated in oxidation mode. The opposite tendency is found for chemical diffusion coefficients. Unlike surface, the oxygen vacancies of the volume region are probably not clustered and have predetermined the higher oxygen diffusion mobility of the sample treated in oxidation mode.

Keywords:

oxygen non-stoichiometry, conductivity, chemical diffusion coefficient, surface exchange coefficient
Received: 09 April 2014 Revised: 19 June 2014 Accepted: 22 June 2014 Published: 02 September 2014 Issue date: September 2014
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Publication history

Received: 09 April 2014
Revised: 19 June 2014
Accepted: 22 June 2014
Published: 02 September 2014
Issue date: September 2014

Copyright

© The author(s) 2014

Acknowledgements

The authors gratefully acknowledge the financial support of the European Union, the Government of Saxony, Germany (SAB Project 14252) and HASYLAB/DESY for X-ray diffraction measurements with synchrotron radiation (Project I-20090287).

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