Controlling structure distortions in 3-layer ferroelectric Aurivillius oxides

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• 作者：Eric J. Nichols^a ; Jiawanjun Shi^a ; Ashfia Huq^b ; Sven C. Vogel^c ; Scott T. Misture^a ; ^{misture@alfred.edu}
• 关键词：Aurivillius ; Ferroelectric ; Photocatalyst ; Multiferroic ; Octahedral distortion
• 刊名：Journal of Solid State Chemistry
• 出版年：2013
• 出版时间：January, 2013
• 年：2013
• 卷：197
• 期：Complete
• 页码：475-482
• 全文大小：940 K

文摘

Combined Rietveld refinements of x-ray and neutron powder diffraction data were used to understand the subtle structure distortions in 3-layer Aurivillius oxides that yield off-centering displacements in ferroelectric and multiferroic compositions. Ferroelectric phases including Bi₂A₂Ti₃O₁₂ (A=La, Pr, Nd, La/Pr, La/Nd, Pr/Nd), Bi₂A₂TiNb₂O₁₂ (A=Ca/Sr, Sr, and Sr/Ba) and Bi₂A₂TiTa₂O₁₂ (A=Ca/Sr, and Sr/Ba) were studied to separate the effects of cation size and charge on the structure distortions and properties. A new approach to describing the local coordination around the Ti, Nb, and/or Ta ions is presented, where the oxygen octahedra are characterized as containing kinks in three dimensions. The kink angles follow trends with the A-site ionic radius and the ferroelectric polarization. The driving force for extensive cation site mixing between the Bi and A-site cations has been clearly established, with site mixing required to maintain interlayer bonding.