Search

We have determined the crystal structures of LiReO3, Li2ReO3and Li2FeV3O8, obtained by Li insertion of ReO3and FeV3O8, by neutron diffraction powder profile analysis. The ReO3host lattice is exclusively corner shared and undergoes significant twisting on Li insertion. The FeV3O8host lattice is extensively edge shared and changes little on Li insertion. The Li is accommodated in 6 coordinate sites in the rhenates and 5 coordinate sites in the iron vanadate.

We have determined a unique model for the mobile copper ion disorder in hexagonal Cu2S between 120° and 325°C via single crystal neutron diffraction. The copper ions partially occupy two sets of three-coordinated sites within the HCP sulfur array and display anharmonic thermal motion. The results suggest that the conductivity is two dimensional in nature.

Diffuse X-ray and neutron scattering have been employed in the study of the mobile ions in many fast ion conductors. In this paper, theoretical and experimental aspects of these techniques and representative experimental studies are briefly discussed.

The diffuse x-ray scattering from single crystal αAgI at 200°C is concentrated in the vicinity of the 200 , 112 , and 400 Bragg peaks. The distribution in reciprocal space is characteristic of l phonon thermal diffuse scattering. The observed scattering is not accounted for, but is not inconsistent with, that predicted by theoretical models for the short range silver ion correlations.

Several examples of compounds with the ReO3structure and shear structures derived from it have been lithiated using n-BuLi. Lithiation of ReO3results in two new hexagonal compositions LiReO3and Li2ReO3which are related to cubic ReO3by a simple twist of the structure. The extensively edge shared structured of FeV3O8forms Li2FeV3O8which contains a similar amount of lithium on a per cavity basis, but cannot undergo this type of twist. Results on similar compounds are also discussed.