The spin lattice relaxation rates and the absorption spectra of7Li in both LiB3O5crystal and glass samples were measured from room temperature up to 800 K. At low temperatures the dominant contribution to the relaxation rates was due to the spin–phonon interaction in both samples. For the crystal the relaxation caused by the diffusion of Li ions became significant above 580 K, and the narrowing of the absorption line started at about 540 K. For the glass the narrowing of the line started at room temperature and the effect of the diffusion of Li ions on the relaxation rate appeared above 400 K. From these results the correlation time &tgr;cof the fluctuating field at Li nuclei was obtained. Each value of the activation energy of &tgr;cdeduced from the relaxation rate and the narrowing of the line, respectively, agreed well. ©1996 American Institute of Physics.