Spinodal Decomposition in the TiO2鈥揤O2 System

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• 作者：Zenji Hiroi ; Hiroaki Hayamizu ; Toru Yoshida ; Yuji Muraoka ; Yoshihiko Okamoto ; Jun-ichi Yamaura ; Yutaka Ueda
• 刊名：Chemistry of Materials
• 出版年：2013
• 出版时间：June 11, 2013
• 年：2013
• 卷：25
• 期：11
• 页码：2202-2210
• 全文大小：528K
• 年卷期：v.25,no.11(June 11, 2013)
• ISSN：1520-5002

文摘

Spinodal decomposition is a ubiquitous phenomenon leading to phase separation from a uniform solution. We show that a spinodal decomposition occurs in a unique combination of two rutile compounds of TiO₂ and VO₂, which are chemically and physically distinguished from each other: TiO₂ is a wide-gap insulator with photocatalytic activities, and VO₂ is assumed to be a strongly correlated electron system which exhibits a dramatic metal鈥搃nsulator transition at 342 K. The spinodal decomposition takes place below 830 K at a critical composition of 34 mol % Ti, generates a unidirectional composition modulation along the c axis with a wavelength of approximately 6 nm, and finally results in the formation of self-assembled lamella structures made up of Ti-rich and V-rich layers stacked alternately with 30鈥?0 nm wavelengths. A metal鈥搃nsulator transition is not observed in quenched solid solutions with intermediate compositions but emerges in the thin V-rich layers as the result of phase separation. Interestingly, the metal鈥搃nsulator transition remains as sharp as in pure VO₂ even in such thin layers and takes place at significantly reduced temperatures of 310鈥?40 K, which is probably due to a large misfit strain induced by lattice matching at the coherent interface.

Keywords:

spinodal decomposition; phase separation; rutile structure; metal鈭抜nsulator transition; TiO₂; VO₂