Guidelines to design multicomponent ferrospinels for high-temperature applications

abstract

This work explores the possibilities to design magnetite-based spinels through multiple simultaneous co-substitutions with transition metal cations, with emphasis on redox behavior and electronic transport. For the first time this approach was assessed for high-temperature applications, which is of particular interest for the development of consumable anodes for pyroelectrolysis, an alternative carbon-lean steelmaking process. A Taguchi plan was used to assess the impact of the concentration of substituting chromium, titanium, manganese and nickel cations on the lattice parameter and electrical conductivity of the multicomponent ferrospinels. The results revealed a comparable decrease in the electrical conductivity, provided by Cr3+, Mn3+/2+ and Ni2+ cations. The impact of Ti4+ was found to be less negative, contributed by the formation of Fe2+ cations and increased hopping probability. The strongest structural impacts, exerted by manganese cations, are likely to affect the mobility of polarons, as revealed by the analysis of the correlation factors for combined effects. Ferrospinels, containing various transition metal cations, are more susceptible to oxidation and phase decomposition, which often result in a sudden conductivity drop and significant dimensional changes in the ceramics. The observed trends for redox behavior suggest that the potential applications of multicomponent ferrospinels in oxidizing conditions are limited to 1000-1400 K due to insufficient stability, while higher temperature applications, requiring significant electronic conductivity, are rather suitable.

keywords

ELECTRICAL-CONDUCTIVITY; SPINEL STRUCTURE; CATION DISTRIBUTION; MAGNETIC-PROPERTIES; REDOX STABILITY; SITE OCCUPANCY; FE-2+ IONS; IRON; NANOPARTICLES; THERMOPOWER

subject category

Chemistry

authors

Ferreira, NM; Ferro, MC; Mikhalev, SM; Costa, FM; Frade, JR; Kovalevsky, AV

Groups

G3 - Electrochemical Materials, Interfaces and Coatings

Projects

CICECO - Aveiro Institute of Materials (UID/CTM/50011/2013)

RMNE-UA-National Network of Electron Microscopy (REDE/1509/RME/2005 )

acknowledgements

Research leading to these results has received support from the European Union's Research Fund for Coal and Steel (RFCS) research program, under grant agreement IERO-RSF-PR-09099. This work was developed within the scope of the project CICECO-Aveiro Institute of Materials, POCI-01-0145-FEDER-007679 (FCT Ref. UID/CTM/50011/2013) and i3N institute with UID/CTM/50025/2013 project, financed by national funds through the FCT/MEC and when appropriate co-financed by FEDER under the PT2020 Partnership Agreement. The support from FCT, Portugal (grant IF/00302/2012) is also acknowledged. M. C. Ferro acknowledges support from RNME - Pole University of Aveiro and FCT project REDE/1509/RME/2005.