In the absence of Li+ ions, the diffusivity of Mn at 920C was less than 9 x 10-11cm2/s. However, when 600ppm of Li+ ions were added, the diffusivity reached values which were of the order of 2 x 10-9cm2/s. This marked enhancement was attributed to the fact that the Li+ ions entered the lattice mainly as interstitials and thereby increased the cation vacancy concentration.

Enhancement by Li+ of the Diffusion of Mn2+ in MgF2 Crystals. J.Toulouse, A.S.Nowick, L.E.Halliburton: Physical Review B, 1982, 26[6], 2926-31