Ionic conductivity of directionally solidified zirconia-mullite eutectics

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• 作者：Ricardo G. Carvalho ; Andrei V. Kovalevsky ; Michael W. Lufaso ; Rui F. Silva ; Florinda M. Costa ; Filipe M. Figueiredo
• 关键词：Zirconia ; Mullite ; Eutectics ; Directional solidification ; Ionic conductivity
• 刊名：Solid State Ionics
• 出版年：1 March, 2014
• 年：2014
• 卷：256
• 期：Complete
• 页码：45-51
• 全文大小：1540 K

文摘

The properties of directionally solidified eutectic (DSE) zirconia-mullite composites are presented. These materials combine two oxide ion conductors in eutectic microstructures stable over broad temperature (570-1415 掳C) and pO₂ (10^鈭?#xA0;20 to 10⁵ Pa) ranges, which are pertinent for their application as high temperature (> 1200 掳C) solid electrolytes, e.g. in Nernstian sensors. X-ray diffraction and scanning electron microscopy/energy dispersive spectroscopy results reveal a composite structure comprising eutectic crystals of mullite and zirconia, and an intergranular amorphous phase rich in Al-Y-Si-O. The amorphous phase is crystallised upon annealing at 1400 掳C, and the resulting composites have a composition close to the nominal eutectic consisting of 79 vol.% mullite and 21 vol.% zirconia. The electrical conductivity of these materials is rationalized in terms of percolation, fraction and properties of each phase, attaining values in excess of 0.01 S/cm at 1370 掳C and displaying Arrhenius behaviour with activation energy of 70 kJ/mol. The broad electrolytic domain of these solid electrolytes is demonstrated by conductivity measurements carried out from 600 掳C to 1370 掳C in O₂, air, Ar and 10%H₂ + 90%N₂ atmospheres.