Abstract
The temperature dependences of the 7 Li NMR line width Δν and spin–lattice relaxation rate 1/ T 1 have been measured in lithium vanadium bronze Li x V 2 O 5 with 0.4 ≦ x ≦1.4 over the temperature range of 77–550 K. The narrowing of Δν has been observed for each sample, which is interpreted in terms of the motional narrowing due to the Li + ionic diffusion. In Li 0.8 V 2 O 5 with a single δ-phase, an activation energy E m for the hopping of Li + ions is estimated to be 0.16±0.05 eV, whereas in Li 0.4 V 2 O 5 the value of 0.10±0.05 eV is deduced for the β-phase. The ionic conductivity σ evaluated from the diffusion coefficient D in Li 0.8 V 2 O 5 at 400 K is 6.3 ×10 -7 Ω -1 cm -1 , which is consistent with the reported value of σ dc ≃10 -7 Ω -1 cm -1 . Below 300 K, 1/ T 1 is considered to be due to magnetic interaction of 7 Li nuclear spins with V 4+ electronic spins. Above 350 K, 1/ T 1 is dominated by Li + ionic diffusion, from which E m is estimated to be 0.10 ±0.05 eV.
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