Abstract
The substitution of Li+ for Zn2+ and Ti4+ for Fe3+ in ZnFe2O4 with the spinel stype structure was adopted to obtain the fundamental understanding of the Li ion conduction in solids. The cation distribution of the compound was investigated at the starting research. The XRD patterns indicated the formation of the solid solution, Zn1-xLixFe2-xTixO4 and the lattice parameter decreased linearly with the increase of x in accordance with the ionic radius for each cation. Above x = 0.6 a slight curvature appeared in the composition dependence of the lattice parameter. The Rietveld analysis determined the cation distribution for the present system. It can be written as Zn1-xFex[8a][Lix/2Fe1-xTix/2][16d]2O4 (for x <0.5). It showed that Li+ occupies the octahedral (16d)site, whereas Fe3+ occurs on the tetrahedral (8a) site. Li+ had a preference for 16d sites up to x = 0.5. On the other hand, Li+ starts out going to the tetrahedral site above a concentration of 0.5. The cation distribution can be written as Zn1-xFe0.5Lix-0.5[8a][Li0.25Fe(1.5-x)2Tix/2][16d]224 (for x> 0.5). The observed change in the composition dependence of the lattice parameter is caused by the change of the cation distribution in the spinel structure. In addition, the iron distribution for the present system was confirmed by the Mossbauer spectroscopy. The electrochemical lithium insertion was also discussed.
