La2SrCr2O7F2: A Ruddlesden–Popper Oxyfluoride Containing Octahedrally Coordinated Cr4+ Centers

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• 作者：Ronghuan Zhang ; Gareth Read ; Franz Lang ; Tom Lancaster ; Stephen J. Blundell ; Michael A. Hayward
• 刊名：Inorganic Chemistry
• 出版年：2016
• 出版时间：March 21, 2016
• 年：2016
• 卷：55
• 期：6
• 页码：3169-3174
• 全文大小：376K
• ISSN：1520-510X

文摘

The low-temperature fluorination of the n = 2 Ruddlesden–Popper phase La₂SrCr₂O₇ yields La₂SrCr₂O₇F₂ via a topochemical fluorine insertion reaction. The structure-conserving nature of the fluorination reaction means that the chromium centers of the initial oxide phase retain an octahedral coordination environment in the fluorinated product, resulting in a material containing an extended array of apex-linked Cr⁴⁺O₆ units. Typically materials containing networks of octahedrally coordinated Cr⁴⁺ centers can only be prepared at high pressure; thus, the preparation of La₂SrCr₂O₇F₂ demonstrates that low-temperature topochemical reactions offer an alternative synthesis route to materials of this type. Neutron diffraction, magnetization, and μ⁺SR data indicate that La₂SrCr₂O₇F₂ undergoes a transition to an antiferromagnetic state below T_N ≈ 140 K. The structure–property relations of this phase and other Cr⁴⁺ oxide phases are discussed.