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Heavy‐Water (D 2 O) Take‐Up‐Induced Lattice Expansion in the High‐Temperature Proton Conductor Ba 3 Ca 1.18 Nb 1.82 O 9−δ
Author(s) -
Papathanassopoulos Konstantinos,
Wenzl Helmut,
Schober Tilman
Publication year - 1997
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1997.tb03268.x
Subject(s) - deuterium , kinetic isotope effect , analytical chemistry (journal) , hydrogen , proton conductor , catalysis , proton , chemistry , water vapor , oxide , lattice (music) , heavy water , inorganic chemistry , materials science , atomic physics , nuclear physics , biochemistry , physics , organic chemistry , electrode , chromatography , acoustics , electrolyte
Dimensional changes of the high‐temperature proton conductor Ba 3 Ca 1.18 Nb 1.82 O 9−δ , when exposed to D 2 O vapor, were investigated using length‐change and precision density measurements. Such information is essential for possible applications of proton conductors in solid oxide fuel cells and humidity and hydrogen sensors. A linear increase of the sample lengths with increases in the deuterium content was observed. Comparison of the present D 2 O data with those that were previously obtained for H 2 O showed that there was a small isotope effect in the lattice expansion. The fact that the length‐change‐versus‐hydrogen‐isotope‐concentration curves were almost isotope independent supported the validity of the take‐up reaction H 2 O( g ) + V Oö + Ox O is an ⇄ 2OH O . In regard to the latter equation, it was found that small islands of silver, palladium, nickel, and platinum act as catalytic promoters of the reaction and lead, for given heavy‐water‐steam exposure conditions, to an increase of water absorption of up to 100%, when compared with samples without the catalytic surface layers.