Construction and dynamic property of the lithium in conductor having rock salt structure

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Li_3InBr_6 is one of the promising compounds for the construction of an all solid-state lithium ion battery. This compound undergoes a phase transition to a superionic phase having rock-salt structure and the conductivity is as high as 2^*10^<-2>Scm just above the superionic phase transition. In order to understand this high conductivity, firstly we tried to synthesize a series of similar compounds and searched new superionic conductors. Secondary we discussed the conduction mechanism by means of various measurements. Following points have become apparent from these experiments.1.The ionic radius of In^<3+> is quite similar to that of Li^+. This fact is most important for the appearance of the superionic phase in the LiX-InX_3 system.2.Na_3InCl_6 did not show high conductivity like Li_3InBr_6. However, we could determine the conduction path of the Na^+ by means of X-ray diffraction and NMR.3.Li_3InBr_6 at the superionic phase was isomorphous with Li_3InCl_6, in which not only Li^+ but In^<3+> are disordered state.4.^7LiNMR suggested that ca 15% of the Li^+ contributed to the conductivity just above the phase transition.5.With increasing temperature the X-ray diffraction pattern changed gradually to a simple one which was characteristic to a rock salt structure. This suggests the appearance of the averaged structure as a result of the rapid cationic diffusion.