High temperature proton conductor Ba sub(3)Ca sub(1.18)Nb sub(1.82)O sub(9- delta ). Part II: Electrochemical cell measurements and TEM

• Published in: Solid state ionics Vol. 118; no. 3-4; pp. 173 - 178
• Main Authors: Schober, T, Bohn, H G, Mono, T, Schilling, W
• Format: Journal Article
• Language: English
• Published: 02.03.1999
• ISSN: 0167-2738

Using oxygen, water-vapor and hydrogen concentration cells and Ba sub(3)Ca sub(1.12)Nb sub(1.82)O sub(9- delta ) (BCN18) as a solid state electrolyte the Nernstian voltages were measured at elevated temperatures. Proton transport numbers near unity were observed for p sub(O2) < 10 super(-5) bar. In the domain of p sub(O2) > 10 super(-5) bar the electron hole transport prevailed over the ionic one, e.g. at p sub(O2) approximately 0.2 bar the proton transport number reached only values of 0.15. Under fuel cell conditions spanning the whole range of p sub(O2) over 23 orders of magnitude an ionic transport number of 0.9 was achieved at 700 degree C. Treatment of BCN18 in hydrogen atmospheres was found to produce a high density of grain boundary cavities leading to pronounced mechanical weakness.