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Cation self and impurity diffusion in poly-crystalline La 0.9 Sr 0.1 Ga 0.9 Mg 0.1 O 2.9

Schulz, Olaf ; Flege, Stefan ; Martin, Manfred (2003):
Cation self and impurity diffusion in poly-crystalline La 0.9 Sr 0.1 Ga 0.9 Mg 0.1 O 2.9.
In: International Symposium on Solid Oxide Fuel Cells <8, 2003, Paris>: Solid oxide fuel cells VIII, SOFC VIII : proceedings .../ ed. S. C. Singhal ...- Pennington, NJ: Electrochemical Soc., 2003.- XX, 1520 S.- (Proceedings volume / Electrochemical Society ;, 7, pp. 304-314, Pennington, NJ, Electrochemical Soc., International symposium on solid oxide fuels cells No8,, Paris , FRANCE, 27. 04. 2003, [Conference or Workshop Item]

Abstract

Cation self-diffusion of 139La, 84Sr and 25Mg and cation impurity diffusion of 144Nd, 89Y and 56Fe in polycrystalline samples of doped lanthanum gallate, La0.9Sr0.1Ga0.9Mg0.1O2.9, was investigated by SIMS for temperatures between 900°C and 1400°C. It was found that diffusion occurs by means of bulk and grain boundaries. The bulk diffusion coefficients are similar for all cations with activation energies which are strongly dependent on temperature. At high temperatures, the activation energies are about 5 eV, while at low temperatures values of about 2 eV are found. These results are explained by a frozen defect structure at low temperatures. This means that the observed activation energy at low temperatures represents only the migration energy of the different cations while the observed activation energy at high temperatures is the sum of the defect formation energy and the migration energy. The migration energies for all cations are nearly identical, although 139La, 84Sr and 144Nd are occupying A-sites while 25Mg and 36Fe are occupying B-sites in the perovskite-structure, To explain these experimental findings we propose a defect cluster containing cation vacancies of both the A- and the B-sublattice and anion vacancies as well.

Item Type: Conference or Workshop Item
Erschienen: 2003
Creators: Schulz, Olaf ; Flege, Stefan ; Martin, Manfred
Title: Cation self and impurity diffusion in poly-crystalline La 0.9 Sr 0.1 Ga 0.9 Mg 0.1 O 2.9
Language: English
Abstract:

Cation self-diffusion of 139La, 84Sr and 25Mg and cation impurity diffusion of 144Nd, 89Y and 56Fe in polycrystalline samples of doped lanthanum gallate, La0.9Sr0.1Ga0.9Mg0.1O2.9, was investigated by SIMS for temperatures between 900°C and 1400°C. It was found that diffusion occurs by means of bulk and grain boundaries. The bulk diffusion coefficients are similar for all cations with activation energies which are strongly dependent on temperature. At high temperatures, the activation energies are about 5 eV, while at low temperatures values of about 2 eV are found. These results are explained by a frozen defect structure at low temperatures. This means that the observed activation energy at low temperatures represents only the migration energy of the different cations while the observed activation energy at high temperatures is the sum of the defect formation energy and the migration energy. The migration energies for all cations are nearly identical, although 139La, 84Sr and 144Nd are occupying A-sites while 25Mg and 36Fe are occupying B-sites in the perovskite-structure, To explain these experimental findings we propose a defect cluster containing cation vacancies of both the A- and the B-sublattice and anion vacancies as well.

Series Name: International Symposium on Solid Oxide Fuel Cells <8, 2003, Paris>: Solid oxide fuel cells VIII, SOFC VIII : proceedings .../ ed. S. C. Singhal ...- Pennington, NJ: Electrochemical Soc., 2003.- XX, 1520 S.- (Proceedings volume / Electrochemical Society ;
Volume: 7
Place of Publication: Pennington, NJ
Publisher: Electrochemical Soc.
Uncontrolled Keywords: SIMS, Magnesium compound, Strontium compound, Lanthanum compound, Gallates, Perovskite, Polycrystal, Solid oxide fuel cell.
Divisions: 11 Department of Materials and Earth Sciences > Material Science > Material Analytics
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences
Event Title: International symposium on solid oxide fuels cells No8,
Event Location: Paris , FRANCE
Event Dates: 27. 04. 2003
Date Deposited: 20 Nov 2008 08:16
Additional Information:

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