Institute of Inorganic Chemistry , Slovak Academy of Sciences , 845 36 Bratislava , Slovakia.
Conditions Extrêmes ét Matériaux: Haute Température et Irradiation, CEMHTI , UPR 3079-CNRS Univ. Orléans , 450 71 , Orléans , France.
Inorg Chem. 2018 Nov 5;57(21):13702-13712. doi: 10.1021/acs.inorgchem.8b02275. Epub 2018 Oct 24.
Precise research on the RbF-AlO system was carried out by means of combining X-ray powder diffraction, high-field solid-state NMR spectroscopy, and thermal analysis methods. α-RbAlF, RbAlO, RbAlO, and new phase, RbAlOF, were identified in the system. The structure of this new rubidium oxofluoroaluminate was determined. It is built up from single layers of oxygen-connected AlOF tetrahedra, those layers beeing separated by fluorine atoms. This type of structure exhibits a decent ionic conductivity at ambient temperature, 1.74 × 10 S cm. The similar structural arrangement of OAl-O-AlO and FOAl-O-AlOF tetrahedra of the conduction planes in RbAlO and RbAlOF were confirmed by Al NMR measurements. A thermal analysis of the RbF-AlO system revealed that it can be defined as a pseudobinary subsystem of the more general quaternary RbF-AlF-AlO-RbO phase diagram. From a phase analysis of individual phase fields, the mutual metastable behavior of all founded phases can be considered. It was observed that fluoro- and oxoaluminates exist together. RbAlOF is more stable under high temperature. Rubidium fluoro- and oxoaluminates are metastable precursors of the thermodynamically more stable structure of rubidium oxofluoroaluminate.
通过结合 X 射线粉末衍射、高场固态 NMR 光谱和热分析方法，对 RbF-AlO 系统进行了精确研究。在该系统中鉴定了 α-RbAlF、RbAlO、RbAlO 和新相 RbAlOF。确定了这种新的 rubidium oxofluoroaluminate 的结构。它由氧连接的 AlOF 四面体的单层构成，这些层由氟原子隔开。这种结构在环境温度下表现出相当高的离子电导率，为 1.74×10^-4 S cm。通过 Al NMR 测量证实了 RbAlO 和 RbAlOF 中传导层中 OAl-O-AlO 和 FOAl-O-AlOF 四面体的类似结构排列。RbF-AlO 系统的热分析表明，它可以定义为更一般的四元 RbF-AlF-AlO-RbO 相图的伪二元子系统。从各个相场的相分析可以考虑所有发现相的相互亚稳行为。观察到氟和氧铝酸盐一起存在。RbAlOF 在高温下更稳定。铷氟和氧铝酸盐是热力学上更稳定的铷氧氟铝酸盐结构的亚稳前体。
