Transport properties of sealants for high-temperature electrochemical applications: RO-BaO-SiO(2) (R = Mg, Zn) glass-ceramics

authors	Pascual, MJ; Kharton, VV; Tsipis, E; Yaremchenko, AA; Lara, C; Duran, A; Frade, JR
nationality	International
journal	JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
author keywords	electrical properties; ionic conductivity; glass ceramics; fuel cells; sealants
keywords	OXIDE FUEL-CELLS; COMPRESSIVE SEALS; OXYGEN; SOFC; CONDUCTIVITY
abstract	The electrical properties and oxygen permeability of glass-ceramics 55SiO(2)-27BaO-18MgO, 55SiO(2)-27BaO-18ZnO and 50SiO(2)-30BaO-20ZnO (%mol), which possess thermal expansion compatible with that of yttria-stabilized zirconia (YSZ) solid electrolytes, were studied between 600 and 950 degrees C in various atmospheres. The ion transference numbers, determined by the modified electromotive force (e.m.f.) technique under oxygen partial pressure gradients of 21 kPa/(1-8) x 10(2) Pa and 21 kPa/(1 x 10(-18)-2 x 10(-12)) Pa, are close to unity both under oxidizing and reducing conditions. The electronic contribution to the total conductivity increases slightly on increasing temperature, but is lower than 2% and 7% for the Zn- and Mg-containing compositions, respectively. The conductivity values measured by impedance spectroscopy vary in the range (1.4-7.8) x 10(-6) S/cm at 950 degrees C under both oxidizing and reducing conditions, with activation energies of 122-154 kJ/mol and a minor increase in H(2)-containing atmospheres, indicating possible proton intercalation. In agreement with the electrical measurements which indicate rather insulating properties of the glass-ceramics, the oxygen permeation fluxes through sintered sealants and through sealed YSZ/glass-ceramics/YSZ cells are very low, in spite of an increase of 15-40% during 200-230 h under a gradient of air/H(2)-H(2)O-N(2) due to slow microstructural changes. (c) 2005 Elsevier Ltd. All rights reserved.
publisher	ELSEVIER SCI LTD
issn	0955-2219
year published	2006
volume	26
issue	15
beginning page	3315
ending page	3324
digital object identifier (doi)	10.1016/j.jeurceramsoc.2005.11.002
web of science category	Materials Science, Ceramics
subject category	Materials Science
unique article identifier	WOS:000241086000034