King Graham, Soliz Jennifer R, Gordon Wesley O
Independent Research Consultant , 4596 Fairway Drive , Los Alamos , New Mexico 87544 , United States.
Edgewood Chemical Biological Center , 5183 Blackhawk Road , Aberdeen Proving Ground , Maryland 21010-5424 , United States.
Inorg Chem. 2018 Mar 5;57(5):2797-2803. doi: 10.1021/acs.inorgchem.7b03137. Epub 2018 Feb 21.
Analysis of X-ray pair distribution function data has provided a detailed picture of the local structure of amorphous Zr(OH) and its thermal decomposition into ZrO. In the untreated phase, the Zr atoms tend to be coordinated by six or seven oxygen atoms. The Zr centered polyhedra connect to each other primarily by sharing edges, but also with a significant amount of corner sharing, to form two-dimensional sheets in which the Zr are connected to an average of about five other Zr. This local structure is related to the structure of monoclinic ZrO and can be derived from it by removing certain Zr neighbors to form sheets and reduce the corner to edge sharing ratio. The maximum correlation length in Zr(OH) is about 12 Å. Heating up to 125 °C results in significant water loss but does not alter the network of Zr and bridging O atoms. Additional water loss caused by heating to 250 °C triggers a reorganization into a new type of amorphous phase with a three-dimensional network and a greater number of Zr-Zr neighbors. Further heating to 330 °C causes crystallization into a mixture of tetragonal and monoclinic ZrO, with the minor tetragonal phase having a smaller average domain size. The tetragonal component vanishes by 900 °C.
对X射线对分布函数数据的分析提供了非晶态Zr(OH)及其热分解为ZrO的局部结构的详细图像。在未处理阶段，Zr原子倾向于由六个或七个氧原子配位。以Zr为中心的多面体主要通过共享边相互连接，但也有大量的角共享，形成二维片层，其中Zr与平均约五个其他Zr相连。这种局部结构与单斜ZrO的结构有关，可以通过去除某些Zr邻居以形成片层并降低角到边的共享比例从其推导出来。Zr(OH)中的最大相关长度约为12 Å。加热到125 °C会导致大量水分流失，但不会改变Zr和桥连O原子的网络。加热到250 °C引起的额外水分流失会引发重组为一种具有三维网络和更多Zr-Zr邻居的新型非晶相。进一步加热到330 °C会导致结晶为四方和单斜ZrO的混合物，少量四方相具有较小的平均畴尺寸。四方相成分在900 °C时消失。
