Thermodynamic Stability of Gadolinia-Doped Ceria Thin Film Electrolytes for Micro-Solid Oxide Fuel Cells

• Published in: Journal of the American Ceramic Society 2007-06, Vol.90 (6), p.1792-1797
• Main Authors: Rupp, Jennifer L.M., Infortuna, Anna, Gauckler, Ludwig J.
• Format: Article
• Language: English
• Subjects: Applied sciences; Cerium oxide; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Electrolytes; Energy; Energy. Thermal use of fuels; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Exact sciences and technology; Fuel cells; Grain size; Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids); Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Microstructure; Nanocrystals; Oxides; Physical properties of thin films, nonelectronic; Physics; Solid oxide fuel cells; Stability; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thermal stability; thermal effects; Thermodynamics; Thin films
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/j.1551-2916.2007.01531.x

Next‐generation micro‐solid oxide fuel cells for portable devices require nanocrystalline thin‐film electrolytes in order to allow fuel cell fabrication on chips at a low operation temperature and with high power outputs. In this study, nanocrystalline gadolinia‐doped ceria (Ce0.8Gd0.2O1.9−x) thin‐film electrolytes are fabricated and their electrical conductivity and thermodynamic stability are evaluated with respect to microstructure. Nanocrystalline gadolinia‐doped ceria thin‐film material (Ce0.8Gd0.2O1.9−x) exhibits a larger amount of defects due to strain in the film than state‐of‐the‐art microcrystalline bulk material. This strain in the film decreases the ionic conductivity of this ionic O2− conductor. The thermodynamic stability of a nanocrystalline ceria solid solution with 65 nm grain size is reduced compared with microcrystalline material with 3–5 μm grain size. Nanocrystalline spray‐pyrolyzed and PLD Ce0.8Gd0.2O1.9−x thin films with average grain sizes larger than 70 nm show predominantly ionic conductivity for temperatures lower than 700°C, which is high enough to be potentially used as electrolytes in low to intermediate‐temperature micro‐solid oxide fuel cells.