abstract
Iron-based oxides are considered as promising consumable anode materials for high temperature pyroelectrolysis. Phase relationships, redox stability and electrical conductivity of Fe3-xAlxO4 spinels were studied at 300-1773 K and p(O-2) from 10(-5) to 0.21 atm. Thermogravimetry/XRD analysis revealed metastability of the sintered ceramics at 300-1300 K. Low tolerance against oxidation leads to dimensional changes of ceramics upon thermal cycling. Activation energies of the total conductivity corresponded to the range of 16-26 kJ/mol at 1450-1773 K in Ar atmosphere. At 1573-1773 K and p(O-2) ranging from 10(-5) to 0.03 atm, the total conductivity of Fe3-xAlxO4 is nearly independent of the oxygen partial pressure. The conductivity values of Fe3-xAlxO4 (0.1 <= x <= 0.4) at 1773 K and p(O-2) similar to 10(-5) to 10(-4) atm were found to be only 1.1-1.5 times lower than for Fe3O4, showing high potential of moderate aluminium additions as a strategy for improvement of refractoriness for magnetite without significant deterioration of electronic transport. (c) 2012 Elsevier Ltd. All rights reserved.
keywords
IRON-ALUMINATE SPINELS; FE-AL-O; CATION DISTRIBUTION; SUBSTITUTED MAGNETITES; ELECTRICAL-PROPERTIES; THERMAL-EXPANSION; PHASE; SYSTEM; DECOMPOSITION; THERMOPOWER
subject category
Materials Science
authors
Kovalevsky, AV; Naumovich, EN; Yaremchenko, AA; Frade, JR
our authors
Aleksey Yaremchenko
Principal Researcher
Andrei Kavaleuski
Principal Researcher
Jorge Ribeiro Frade
Retired Professoracknowledgements
Research leading to these results has received funding from the European Union's Research Fund for Coal and Steel (RFCS) research program, under grant agreement IERO-RSF-PR-09099, from the European Commission within the project NMP2/CT/2004/515960