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Mixed Ionic-Electronic Conductivity, Redox Behavior and Thermochemical Expansion of Mn-Substituted 5YSZ as an Interlayer Material for Reversible Solid Oxide Cells.
- Source :
-
Materials (Basel, Switzerland) [Materials (Basel)] 2021 Jan 30; Vol. 14 (3). Date of Electronic Publication: 2021 Jan 30. - Publication Year :
- 2021
-
Abstract
- Manganese-substituted 5 mol.% yttria-stabilized zirconia (5YSZ) was explored as a prospective material for protective interlayers between electrolyte and oxygen electrodes in reversible solid oxide fuel/electrolysis cells. [(ZrO <subscript>2</subscript> ) <subscript>0.95</subscript> (Y <subscript>2</subscript> O <subscript>3</subscript> ) <subscript>0.05</subscript> ] <subscript>1- x </subscript> [MnO <subscript>y</subscript> ] <subscript>x</subscript> ( x = 0.05, 0.10 and 0.15) ceramics with cubic fluorite structure were sintered in air at 1600 °C. The characterization included X-ray diffraction (XRD), scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), thermogravimetry and dilatometry in controlled atmospheres, electrical conductivity measurements, and determination of oxygen-ion transference numbers by the electromotive force (EMF) technique. Mn-substituted 5YSZ solid solutions exhibit variable oxygen nonstoichiometry with manganese cations in a mixed 2+/3+ oxidation state under oxidizing conditions. Substitution by manganese gradually increases the extent of oxygen content variation on thermal/redox cycling, chemical contribution to thermal expansion and dimensional changes on reduction. It also deteriorates oxygen-ionic conductivity and improves p -type electronic conductivity under oxidizing conditions, leading to a gradual transformation from predominantly ionic to prevailing electronic transport with increasing x . Mn <superscript>2+/3+</superscript> →Mn <superscript>2+</superscript> transformation under reducing atmospheres is accompanied by the suppression of electronic transport and an increase in ionic conductivity. All Mn-substituted 5YSZ ceramics are solid electrolytes under reducing conditions. Prolonged treatments in reducing atmospheres, however, promote microstructural changes at the surface of bulk ceramics and Mn exsolution. Mn-substituted 5YSZ with 0.05 ≤ x < 0.10 is considered the most suitable for the interlayer application, due to the best combination of relevant factors, including oxygen content variations, levels of ionic/electronic conductivity and thermochemical expansion.
Details
- Language :
- English
- ISSN :
- 1996-1944
- Volume :
- 14
- Issue :
- 3
- Database :
- MEDLINE
- Journal :
- Materials (Basel, Switzerland)
- Publication Type :
- Academic Journal
- Accession number :
- 33573317
- Full Text :
- https://doi.org/10.3390/ma14030641