DEFECT STRUCTURE AND LI-VACANCY ORDERING IN BETA-LIGA

The relationship between the defect structure and the Li-vacancy order ing in beta-LiGa [NaTl structure (space group Fd3m) ranging in Li cont ent (C-Li) from about 44 to 54 at. %] has been studied. According to t he dependence of lattice parameter and density on CU we propose a mode l that the defect structure in the beta phase consists of two types of defects, namely Li vacancy (V-Li) and Li antisite (Li-Ga) V-Li is the dominant defect for the Li-deficient compositions and Li-Ga is the do minant one for the Li-excess ones. It is suggested that the strain ene rgy arising from the point defects is released by forming a V-Li-Li-Ga complex defect in the wide beta phase. The Li-vacancy ordering, which induces an anomalous electrical resistivity at around 230 K, is obstr ucted by the formation of the complex defect.