Oxygen Isotope Transport Properties of Yttria‐Stabilized Zirconia (YSZ) in O2‐ and H2O‐Containing Atmospheres. Issue 5 (26th July 2013)

• Record Type: Journal Article
• Authors: Pietrowski, M. J.; De Souza, R. A.; Fartmann, M.; ter Veen, R.; Martin, M.
• Is Part Of: Fuel cells. Volume 13:Issue 5(2013:Oct.)
• Page Start: 673
• Page End: 681
• Publication Date: 2013-07-26
• Subjects: Fuel cells -- Periodicals; 621.312429
• DOI: 10.1002/fuce.201300087
• Languages: English
• ISSNs: 1615-6846

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>Oxygen isotope exchange experiments, H<sub>2</sub><sup>18</sup>O/H<sub>2</sub><sup>16</sup>O ("wet" anneals) and <sup>18</sup>O<sub>2</sub>/<sup>16</sup>O<sub>2</sub> ("dry" anneals), were performed on single crystal samples of yttria‐stabilized zirconia (YSZ) at a temperature of <italic>T</italic> = 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 (<italic>D</italic>*) and oxygen tracer surface exchange coefficients (<italic>k</italic>*), from both the polished (smooth) and unpolished (rough) sides of single crystal samples, as a function of water partial pressure <italic>p</italic>H<sub>2</sub>O and oxygen partial pressure <italic>p</italic>O<sub>2</sub>. Isothermal values of <italic>D</italic>* were found to depend on neither <italic>p</italic>O<sub>2</sub> nor <italic>p</italic>H<sub>2</sub>O (nor surface roughness). Isothermal values of <italic>k</italic>*, in contrast, displayed a strong dependence on <italic>p</italic>O<sub>2</sub> or <italic>p</italic>H<sub>2</sub>O; <italic>k</italic>*<sub>wet</sub> was, in addition, 2–3 orders of magnitude higher than <italic>k</italic>*<sub>dry</sub>. Surprisingly, surface roughness had little effect on <italic>k</italic>*<sub>wet</sub>, whereas rough surfaces exhibited much higher <italic>k</italic>*<sub>dry</sub> values than smooth surfaces. Data for <italic>k</italic>*<sub>wet</sub> obtained as a function of temperature at <italic>p</italic>H<sub>2</sub>O = 18 mbar show a change in activation enthalpy at <italic>T</italic> ≈ 973 K. The behavior of <italic>k</italic>* is discussed in terms of surface composition, surface area and surface reaction mechanisms.</p> </abstract>