Departamento de Física Aplicada-ICMUV, MALTA Consolider Team , Universidad de Valencia, Edificio de Investigación , C/Dr. Moliner 50 , Burjassot 46100 Valencia , Spain.
Universidad de Buenos Aires , Consejo Nacional de lnvestigaciones Científicas y Técnicas. Instituto de Tecnología y Ciencias de la Ingeniería 'Ing. Hilario Fernández Long' (INTECIN) . Av. Paseo Colón 850 , C1063ACV Ciudad Autónoma de Buenos Aires , Argentina.
Inorg Chem. 2019 Apr 1;58(7):4480-4490. doi: 10.1021/acs.inorgchem.8b03648. Epub 2019 Mar 13.
We present a study of the pressure dependence of the structure of partially hydrated hexagonal CePO up to 21 GPa using synchrotron powder X-ray diffraction. At a pressure of 10 GPa, a second-order structural phase transition is observed, associated with a novel polymorph. The previously unknown high-pressure phase has a monoclinic structure with a similar atomic arrangement as the low-pressure phase, but with reduced symmetry, belonging to space group C2. Group-subgroup relations hold for the space symmetry groups of both structures. There is no detectable volume discontinuity at the phase transition. Here we provide structural information on the new phase and determine the axial compressibility and bulk modulus for both phases. They are found to have an anisotropic behavior and to be much more compressible than the denser monazite-like polymorph of CePO. In addition, the isothermal compressibility tensor for the high-pressure structure is reported at 10 GPa and the direction of maximum compressibility described. Finally, the possible role of water and the pressure medium in the high-pressure behavior is discussed. The results are compared with those from other rare-earth orthophosphates.
我们使用同步辐射粉末 X 射线衍射研究了部分水合六方 CePO 的压力依赖性，最高可达 21 GPa。在 10 GPa 的压力下，观察到与一种新的多晶型物相关的二级结构相变。先前未知的高压相具有单斜结构，与低压相具有相似的原子排列，但对称性降低，属于空间群 C2。两个结构的空间对称群都符合群-子群关系。在相变处没有可检测到的体积不连续性。在此，我们提供了新相的结构信息，并确定了两相的轴向压缩率和体弹模量。结果表明，它们的各向异性行为比 CePO 的更密集的独居石型多晶型物更具可压缩性。此外，还报道了 10 GPa 下高压结构的等温压缩率张量，并描述了最大压缩率的方向。最后，讨论了水和压力介质在高压行为中的可能作用。将结果与其他稀土正磷酸盐进行了比较。
