Structure superstructure relationships in lithium metaborate meta‐aluminate compounds

The structure of Li₂BAlO₄ has been recently solved by powder x‐ray diffraction. It consists of infinite chains of meta‐aluminate tetrahedra which are crosslinked by metaborate triangles and charge balanced by four coordinated lithium atoms. In this work we employ the method of similarity operators to describe rigorously the structure superstructure relationships between Li₂BAlO₄, α‐ LiBO₂ and γ‐LiAlO₂ based on the wurtzite and zinc‐blende prototype structures. These relationships are complemented by vibrational spectroscopic comparison of the three crystalline compounds. α‐LiBO₂ and γ‐LiAlO₂ are the end members of the pseudobinary lithium metaborate metaaluminate join and also the products of Li₂BAlO₄ dissociation above ∼890°C. Therefore the results are employed to suggest the nature of high temperature chemical transformations in the Li₂O–B₂O₃–Al₂O₃ phase diagram.