Premium
Proton Conductor Ba3Ca 1.18 Nb1.82O9‐delta (BCN18): Effect of Reducing Environments
Author(s) -
Schober Tilman,
Friedrich Jochen
Publication year - 1999
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.1151-2916.1999.tb02212.x
Subject(s) - enthalpy , hydrogen , delta , chemistry , exothermic reaction , proton , thermogravimetry , oxygen , valence (chemistry) , analytical chemistry (journal) , thermodynamics , inorganic chemistry , physics , organic chemistry , chromatography , astronomy , quantum mechanics
The compound Ba 3 Ca 1.18 Nb 1.82 O 9‐delta (BCN18) has been discussed recently as a promising high‐temperature proton conductor. Oxygen loss under very reducing conditions has been determined quantitatively using thermogravimetry. The thermodynamic parameters Delta H ° O = 2.58 ± 0.06 eV and Delta S ° O = 1.06 × 10 ‐3 eV/K provide a suitable thermodynamic description for the equation O × O right arrow ½O 2 + V ·· O + 2 e ´. Enthalpy and entropy of the hydrogen absorption reaction have been determined indirectly for BCN18: Delta H ° H = ‐0.8 eV and Delta S ° H = ‐6.6 × 10 ‐4 eV/K. Hydrogen absorption is, therefore, an exothermic process. Valence changes where Nb 5+ + e ´ right arrow Nb 4+ also have been taken into account under reducing conditions.