Redox stability and high-temperature electrical conductivity of magnesium-and aluminium-substituted magnetite

authors	Kovalevsky, AV; Yaremchenko, AA; Naumovich, EN; Ferreira, NM; Mikhalev, SM; Costa, FM; Frade, JR
nationality	International
journal	JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
author keywords	Electrical conductivity; Thermal expansion; Spinel; Redox stability; Magnetite
keywords	MOLTEN IRON-OXIDE; THERMAL-EXPANSION; SPINEL; THERMOPOWER; SIMULATION; PROGRAM; GULP; MN
abstract	Spinel-type magnetite-based oxides, possessing relatively high electrical conductivity, are considered as promising consumable anode materials for high temperature pyroelectrolysis, a breakthrough low-CO2 steel technology to overcome the environmental impact of classical extractive metallurgy. The present work was focused on the analysis of phase stability, thermal expansion and high-temperature electrical conductivity in (Fe,Mg,Al)(3)O-4 system under oxidizing and mildly reducing conditions. Metastable, nearly single-phase at room temperature (Fe,Mg,Al)(3)O-4 ceramics was obtained by sintering at 1753-1773 K for 10 h in argon atmosphere. Thermal expansion and redox induced dimensional changes were studied on heating, using TG, XRD and dilatometry. The results revealed that magnesium improves the tolerance against oxidative decomposition and minimizes unfavorable dimensional changes in ceramic samples upon thermal cycling. Co-substitution of iron with aluminium and magnesium was proved to be a promising strategy for improvement of refractoriness and phase stability of Fe3O4-based spinels at elevated temperatures, without significant reduction in the electrical conductivity. (C) 2013 Elsevier Ltd. All rights reserved.
publisher	ELSEVIER SCI LTD
issn	0955-2219
year published	2013
volume	33
issue	13-14
beginning page	2751
ending page	2760
digital object identifier (doi)	10.1016/j.jeurceramsoc.2013.04.008
web of science category	Materials Science, Ceramics
subject category	Materials Science
unique article identifier	WOS:000321803400042