McCoy Sabrina E A, Salasin John R, Everett S Michelle, Rawn Claudia J
Department of Materials Science and Engineering, University of Tennessee, Knoxville, USA.
BWX Technologies, Lynchburg, VA, USA.
Sci Rep. 2020 Oct 1;10(1):16311. doi: 10.1038/s41598-020-73311-w.
CaGaO was successfully synthesized using a wet chemistry technique to promote the homogenous mixing of the Ca and Ga cations. Rietveld refinements on X-ray and neutron powder diffraction data confirm that the compound is isostructural to CaAlO however, with a significantly larger lattice parameter allowing for the cages that result from the framework arrangement to expand. In naturally occurring CaAlO, the mineral mayenite, these cages are occupied by O anions, however, experimental studies exchanging the O anions with other anions has led to a host of applications, depending on the caged anion. The functional nature of the structure, where framework distortions coupled with cage occupants, are correlated to electronic band structure and modifications to the framework could lead to interesting physical properties. The phase evolution was tracked using thermogravimetric analysis and high temperature X-ray diffraction and showed a lower formation temperature for the CaGaO analogue compared to CaAlO synthesized using the same wet chemistry technique. Analyzing both X-ray and neutron powder diffraction using the Rietveld method with two different starting models results in one structural model, with one Ca position and the caged O on a 24d special position, being preferred.
采用湿化学技术成功合成了CaGaO，以促进Ca和Ga阳离子的均匀混合。对X射线和中子粉末衍射数据进行的Rietveld精修证实，该化合物与CaAlO同构，然而，其晶格参数明显更大，使得框架排列产生的笼能够扩展。在天然存在的CaAlO（钙铝石矿物）中，这些笼被O阴离子占据，然而，用其他阴离子交换O阴离子的实验研究已导致了许多应用，这取决于被笼住的阴离子。结构的功能性质，即框架畸变与笼中占据物相关，与电子能带结构相关，并且框架的修饰可能导致有趣的物理性质。使用热重分析和高温X射线衍射追踪相演变，结果表明，与使用相同湿化学技术合成的CaAlO相比，CaGaO类似物的形成温度更低。使用Rietveld方法对两种不同的起始模型进行X射线和中子粉末衍射分析，结果得到一个结构模型，其中一个Ca位置和笼中的O处于24d特殊位置，此模型更受青睐。
