Single Crystals of C12A7 (Ca12Al14O33) Substituted with 1 mol % Iron

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• 作者：Stefan G. Ebbinghaus ; Holger Krause ; Doh-Kwon Lee ; J眉rgen Janek
• 刊名：Crystal Growth & Design
• 出版年：2014
• 出版时间：May 7, 2014
• 年：2014
• 卷：14
• 期：5
• 页码：2240-2245
• 全文大小：285K
• 年卷期：v.14,no.5(May 7, 2014)
• ISSN：1528-7505

文摘

Single crystals of Ca₁₂Al₁₄O₃₃ (C12A7, mayenite) substituted with 1 mol % Fe were grown by the floating zone technique in an atmosphere of 2% O₂/98% N₂. The iron substitution leads to an increase of the unit cell parameter by roughly 0.002 脜. Optical spectroscopy reveals an additional broad absorption band at 310 nm for the iron-substituted sample reflecting the yellow color of the crystals. XANES measurements at the Fe鈥揔 absorption edge prove the incorporation of Fe³⁺ on the aluminum sites. Measurements of the magnetic susceptibility resulted in a value of 5.8 渭_B per iron ion as expected for high-spin Fe³⁺. C12A7 is known to be a very good oxygen ion conductor at high temperatures. In pure oxygen, the iron substitution leads to a slightly reduced conductivity between approximately 500 and 800 掳C, while at higher temperatures, the conductivity is very similar to the pristine material. Under reducing conditions, the slope of log(蟽) vs log(p(O₂)) of the iron-substituted sample was found to be steeper than that for pure C12A7.