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Thermogravimetric Study of the M‐Co‐O System: I, M = Ta and Nb at 1200°C
Author(s) -
Kitayama Kenzo
Publication year - 1992
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.1151-2916.1992.tb04208.x
Subject(s) - thermogravimetric analysis , oxygen , ternary numeral system , partial pressure , ternary operation , phase (matter) , lattice constant , analytical chemistry (journal) , solid solution , phase diagram , chemistry , materials science , thermodynamics , metallurgy , physics , diffraction , organic chemistry , chromatography , computer science , optics , programming language
Phase equilibria in the Ta‐Co‐O and Nb‐Co‐O systems have been studied at 1200°C at oxygen partial pressures from 10 −0.68 to 10 −13.50 atm for the former and from 10 −0.68 to 10 −13.30 atm for the latter. In both systems, M 2 CoO 6 and M 2 Co 4 O 9 are stable ternary compounds under the experimental conditions, and a new phase, Nb 5 Co 2 O 14 , has been identified. The Ta‐Co‐O system is simple, whereas the Nb‐Co‐O system is somewhat more complicated because of the extra phase. The lattice constants of the ternary compounds have been determined and compared with previous values. The standard Gibbs energies of reactions have been determined using oxygen partial pressures in equilibrium with three solid phases.