Defect structure and Li-vacancy ordering in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>β</mml:mi></mml:math>-LiGa

Abstract

The relationship between the defect structure and the Li-vacancy ordering in $\ensuremath{\beta}$-LiGa [NaTl structure (space group $\mathrm{Fd}3m$) ranging in Li content (${C}_{\mathrm{Li}}$) from about 44 to 54 at.%] has been studied. According to the dependence of lattice parameter and density on ${C}_{\mathrm{Li}}$, we propose a model that the defect structure in the $\ensuremath{\beta}$ phase consists of two types of defects, namely Li vacancy (${V}_{\mathrm{Li}}$) and Li antisite (${\mathrm{Li}}_{\mathrm{Ga}}$). ${V}_{\mathrm{Li}}$ is the dominant defect for the Li-deficient compositions and ${\mathrm{Li}}_{\mathrm{Ga}}$ is the dominant one for the Li-excess ones. It is suggested that the strain energy arising from the point defects is released by forming a ${V}_{\mathrm{Li}}$-${\mathrm{Li}}_{\mathrm{Ga}}$ complex defect in the wide $\ensuremath{\beta}$ phase. The Li-vacancy ordering, which induces an anomalous electrical resistivity at around 230 K, is obstructed by the formation of the complex defect.