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Limits of the Thermodynamic Stability of Cobalt—Iron—Manganese Mixed Oxides at 1200°C
Author(s) -
Subramanian Ramesh,
Dieckmann Rüdiger
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.tb08191.x
Subject(s) - spinel , partial pressure , cobalt , thermogravimetric analysis , manganese , ternary operation , materials science , oxygen , analytical chemistry (journal) , mole fraction , chemical stability , electrochemistry , oxide , mineralogy , thermodynamics , chemistry , metallurgy , electrode , physics , organic chemistry , chromatography , computer science , programming language
The thermodynamic stability of spinel and rock‐salt structure phases has been investigated for the quasi‐ternary mixed oxide system Co‐Fe‐Mn‐O at 1200°C and at total pressures of the order of 1 atm (∼1.01 × 10 5 Pa) using thermogravimetric and electrical conductivity measurements. The results reveal the stability limits of the spinel and rock‐salt structure phases with varying cationic composition and oxygen partial pressure at 1200°C. The oxygen partial pressure was varied over 12 orders of magnitude, from log 10 a o2 = 0 to log 10 a o2 = ‐12, by using CO/CO 2 and N 2 /O 2 gas mixtures and monitored by an electrochemical, stabilized zirconia‐based EMF cell. The maximum cobalt mole fraction used in the investigation was about 0.33.