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Oxygen Isotope Transport Properties of Yttria‐Stabilized Zirconia (YSZ) in O 2 ‐ and H 2 O‐Containing Atmospheres
Author(s) -
Pietrowski M. J.,
De Souza R. A.,
Fartmann M.,
ter Veen R.,
Martin M.
Publication year - 2013
Publication title -
fuel cells
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.485
H-Index - 69
eISSN - 1615-6854
pISSN - 1615-6846
DOI - 10.1002/fuce.201300087
Subject(s) - analytical chemistry (journal) , yttria stabilized zirconia , oxygen , isothermal process , partial pressure , chemistry , cubic zirconia , surface roughness , diffusion , secondary ion mass spectrometry , materials science , mineralogy , ion , thermodynamics , ceramic , physics , organic chemistry , chromatography , composite material
Oxygen isotope exchange experiments, H 2 18 O/H 2 16 O (”wet” anneals) and 18 O 2 / 16 O 2 (”dry” anneals), were performed on single crystal samples of yttria‐stabilized zirconia (YSZ) at a temperature of T = 1073 K with subsequent determination of the oxygen isotope profiles in the solid by time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS). Such experiments yielded oxygen tracer diffusion coefficients ( D *) and oxygen tracer surface exchange coefficients ( k *), from both the polished (smooth) and unpolished (rough) sides of single crystal samples, as a function of water partial pressure p H 2 O and oxygen partial pressure p O 2 . Isothermal values of D * were found to depend on neither p O 2 nor p H 2 O (nor surface roughness). Isothermal values of k *, in contrast, displayed a strong dependence on p O 2 or p H 2 O; k * wet was, in addition, 2–3 orders of magnitude higher than k * dry . Surprisingly, surface roughness had little effect on k * wet , whereas rough surfaces exhibited much higher k * dry values than smooth surfaces. Data for k * wet obtained as a function of temperature at p H 2 O = 18 mbar show a change in activation enthalpy at T ≈ 973 K. The behavior of k * is discussed in terms of surface composition, surface area and surface reaction mechanisms.