Errandonea D, Garg A B, Pellicer-Porres J, Martinez-Garcia D, Popescu C
Departament de Física Aplicada-ICMUV, Universitat de València, Dr. Moliner 50, 46100 Burjassot, Spain.
J Phys Condens Matter. 2019 Dec 4;31(48):485401. doi: 10.1088/1361-648X/ab3c31. Epub 2019 Aug 19.
The promising technological material EuBiVO, has been studied for the first time at room-temperature under high-pressure, up to 24.9 GPa, by means of in situ angle dispersive powder x-ray diffraction (XRD). The compound undergoes two phase transitions at 1.9 and 16.1 GPa. The first transition is from the monoclinic fergusonite-type structure (space group I2/a) to a tetragonal scheelite-type structure (space group I4/a), being a ferroelastic-paraelastic transformation similar to that previously reported for isomorphic pristine BiVO. The second phase transition is first-order in nature. The scheelite-type and the second high-pressure phase coexist in a wide pressure range. A monoclinic structure (space group P2/n) is proposed for the second high-pressure phase. Both transitions are reversible upon decompression. Details of the different crystal structures are reported. All the three observed structures are composed of network of VO tetrahedra and BiO (or EuO due to the substitution of Bi by Eu) dodecahedra. The room-temperature P-V equation of state and axial anisotropic compressibilities of the fergusonite and scheelite polymorphs are also given. In particular, the isothermal compressibility tensor for the monoclinic fergusonite phase has been calculated.
有前景的技术材料EuBiVO首次在室温及高达24.9 GPa的高压下通过原位角散射粉末X射线衍射（XRD）进行了研究。该化合物在1.9 GPa和16.1 GPa处经历了两次相变。第一次转变是从单斜铁铌钇矿型结构（空间群I2/a）转变为四方白钨矿型结构（空间群I4/a），这是一种类似于先前报道的同构原始BiVO的铁弹性-顺弹性转变。第二次相变本质上是一级相变。白钨矿型和第二种高压相在很宽的压力范围内共存。第二种高压相被认为具有单斜结构（空间群P2/n）。减压时，两次转变都是可逆的。报告了不同晶体结构的细节。观察到的所有三种结构均由VO四面体和BiO（由于Eu取代Bi，也可能是EuO）十二面体网络组成。还给出了室温下铁铌钇矿和白钨矿多晶型的P-V状态方程和轴向各向异性压缩率。特别是，计算了单斜铁铌钇矿相的等温压缩张量。
