Chemically Induced Expansion of La2NiO4+-Based Materials
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- 作者：Vladislav V. Kharton ; Andrei V. Kovalevsky ; Maxim Avdeev ; Ekaterina V. Tsipis ; Mikhail V. Patrakeev ; Aleksey A. Yaremchenko ; Eugene N. Naumovich ; Jorge R. Frade
- 刊名：Chemistry of Materials
- 出版年：2007
- 出版时间：April 17, 2007
- 年：2007
- 卷：19
- 期：8
- 页码：2027 - 2033
- 全文大小：255K
- 年卷期：v.19,no.8(April 17, 2007)
- ISSN：1520-5002
文摘
The equilibrium chemical strains induced by the oxygen hyperstoichiometry variations in mixed-conducting La2Ni1-xMxO4+
(M = Fe, Co, Cu; x = 0-0.2) with K2NiF4-type structure, were studied bycontrolled-atmosphere dilatometry at 923-1223 K in the oxygen partial pressure range 5 × 10-4 to 0.7atm. In combination with the oxygen content measured by coulometric titration and thermogravimetry,the results reveal a very low chemical expansivity, favorable for high-temperature electrochemicalapplications. Under oxidizing conditions, the isothermal expansion relative to atmospheric oxygen pressure(
C) is less than 0.02%. The ratio between these values and the corresponding nonstoichiometry incrementvaries from -3 × 10-3 to 6 × 10-3, which is much lower compared to most permeable mixed conductorsderived from perovskite-like cobaltites and ferrites. Consequently, the chemical contribution to apparentthermal expansion coefficients at a fixed oxygen pressure, (13.7-15.1) × 10-6 K-1, does not exceed5%. The high-temperature X-ray diffraction studies showed that this behavior results from stronglyanisotropic expansion of the K2NiF4-type lattice, namely the opposing variations of the unit-cell parameterson changing oxygen stoichiometry.
(M = Fe, Co, Cu; x = 0-0.2) with K2NiF4-type structure, were studied bycontrolled-atmosphere dilatometry at 923-1223 K in the oxygen partial pressure range 5 × 10-4 to 0.7atm. In combination with the oxygen content measured by coulometric titration and thermogravimetry,the results reveal a very low chemical expansivity, favorable for high-temperature electrochemicalapplications. Under oxidizing conditions, the isothermal expansion relative to atmospheric oxygen pressure(C) is less than 0.02%. The ratio between these values and the corresponding nonstoichiometry incrementvaries from -3 × 10-3 to 6 × 10-3, which is much lower compared to most permeable mixed conductorsderived from perovskite-like cobaltites and ferrites. Consequently, the chemical contribution to apparentthermal expansion coefficients at a fixed oxygen pressure, (13.7-15.1) × 10-6 K-1, does not exceed5%. The high-temperature X-ray diffraction studies showed that this behavior results from stronglyanisotropic expansion of the K2NiF4-type lattice, namely the opposing variations of the unit-cell parameterson changing oxygen stoichiometry.