Structure superstructure relationships in lithium metaborate meta-aluminate compounds

摘要

The structure of Li_2BalO_4 has been recently solved by powder x-ray diffraction. It consists of infinite chains of meta-aluminate tetrahedral 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 Li_2BAlO_4, #alpha#-LiBO_2 and #gamma#-LiAlO_2 based on the wurtzite and zinc-blende prototype structures. These relationships are complemented by vibrational spectroscopic comparison of the three crystalline compounds. #alpha#-LiBO_2 and #gamma#-LiAlO_2 are end members of the pseudobinary lithium metaborate metaaluminate join and also the products of Li_2BAlO_4 dissociation above approx 890 deg C. Therefore the results are employed to suggest the nature of high temperature chemical transformations in the Li_2O-B_2O_3-Al_2O_3 phase diagram.