NMR Study on Defect Structure in β-LiGa

The mechanism of superionic conductivity in β-LiGa has been investigated by 7 Li and 71 Ga NMR spin–lattice relaxation rates 1/ T 1 in Li excess 50.0 at. %, Li deficient 44.0 and 47.0 at. % samples. The activation energies of Li + ionic diffusions through free Li vacancy V Li and through bound Li vacancy trapped by antisite Li Ga have been estimated to be 0.13 and 0.064 eV by applying Bloembergen–Purcell–Pound (BPP) type equation to 1/ T 1 in 50.0 at. % Li sample. In Li deficient samples, the same activation energy, 0.11–0.13 eV, for Li + ionic diffusion through free V Li has been obtained at high temperatures, and evidence for the ordering of V Li has been also detected by anomalies at 200–240 K in the temperature dependence of 1/ T 1 for 7 Li. However, the motional narrowing observed in 7 Li NMR line width above 110–130 K indicates that disorder in V Li can still remain even below its ordering temperature in 44.0 and 47.0 at. % Li samples.