Synthesis and Characterization of the Aurivillius Phase CoBi2O2F4.
Synthesis and Characterization of the Aurivillius Phase CoBi2O2F4.
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Aurivilius 相 CoBi2O2F4 的合成和表征。
DOI：
10.1021/acs.inorgchem.8b01118
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发表时间：
2018
影响因子：
4.6
通讯作者：
M. Johnsson
中科院分区：
文献类型：
--
作者：
Eleni Mitoudi Vagourdi;Silvia Müllner;P. Lemmens;R. Kremer;M. Johnsson
采用水热法在230 ° C合成了CoBi2O2F4化合物。单晶X射线衍射数据用于确定晶体结构。该化合物是层状的，属于Aurivillius家族化合物。本发明化合物是第一个含Co 2+的氧氟Aurivillius相。通过用F-离子部分取代O2-，实现了包含具有2+这样低氧化态的d区阳离子。晶体结构在四元非中心对称空间群I4和c = 16.341（8）。晶体结构由两个主要结构单元组成：[BiO 4F 4]扭曲立方体和[CoF 6]八面体。有趣的是，由于八面体[CoF6]在四个等效位置之间倾斜，因此F原子在室温下占据4倍分裂位置。对于结构无序的调查，拉曼散射数据收集的范围从10 K到室温。随着温度的降低，出现了更尖锐的声子峰，并清楚地出现了几个模式，这表明无序的减少。磁化率和热容量的测量证明了长程反铁磁有序低于Néel温度150 K。磁化率在75K以上符合居里-外斯定律，居里-外斯温度θ CW =-142（2）K。
The new CoBi2O2F4 compound was synthesized by a hydrothermal method at 230 °C. Single-crystal X-ray diffraction data were used to determine the crystal structure. The compound is layered and belongs to the Aurivillius family of compounds. The present compound is the first oxo-fluoride Aurivillius phase containing Co2+. Inclusion of a d-block cation with such a low oxidation state as 2+ was achieved by partially replacing O2- with F- ions. The crystal structure is best described in the tetragonal noncentrosymmetric space group I4̅ with unit-cell parameters a = 3.843(2) Å and c = 16.341(8) Å. The crystal structure consists of two main building units: [BiO4F4] distorted cubes and [CoF6] octahedra. Interestingly, since the octahedra [CoF6] tilt between four equivalent positions, the F atoms occupy a 4-fold split position at room temperature. For the investigation of the structural disorder, Raman scattering data were collected in the range from 10 K to room temperature. As the temperature decreases, sharper phonon peaks appear and several modes clearly appear, which indicates a reduction of the disorder. Magnetic susceptibility and heat capacity measurements evidence long-range antiferromagnetic ordering below the Néel temperature of ∼50 K. The magnetic susceptibility is in agreement with the Curie-Weiss law above 75 K with a Curie-Weiss temperature of θCW = -142(2) K.