High-temperature conductivity, stability and redox properties of Fe_{3?span style='font-style: italic'>x}Al_xO₄ spinel-type materials

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• 作者：Andrei V. Kovalevsky ; ^{akavaleuski@ua.pt} ; Eugene N. Naumovich ; Aleksey A. Yaremchenko ; Jorge R. Frade
• 关键词：Electrical conductivity ; Thermal expansion ; Spinels ; Redox stability
• 刊名：Journal of the European Ceramic Society
• 出版年：2012
• 出版时间：September, 2012
• 年：2012
• 卷：32
• 期：12
• 页码：3255-3263
• 全文大小：1334 K

文摘

Iron-based oxides are considered as promising consumable anode materials for high temperature pyroelectrolysis. Phase relationships, redox stability and electrical conductivity of Fe_3?em>xAl_xO₄ spinels were studied at 300-1773 K and p(O₂) from 10^? 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(O₂) ranging from 10^? to 0.03 atm, the total conductivity of Fe_3?em>xAl_xO₄ is nearly independent of the oxygen partial pressure. The conductivity values of Fe_3?em>xAl_xO₄ (0.1 ?#xA0;x ?#xA0;0.4) at 1773 K and p(O₂) ?0^? to 10^? 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.