A new solid solution series linking LiTi2O4 and Li2Ti3O7 ramsdellites: A combined X-ray and neutron study

We report the discovery of a new solid solution linking the LiTi2O4 and Li2 Ti3O7 ramsdellite phases. The solid solution system is Li1+xTi2-2xO4 (0 les s than or equal to x less than or equal to 0.143), where Li2Ti3O7 can be wr itten as Li1.143Ti1.714O4. Combined Rietveld refinement of X-ray and neutro n diffraction data sets has been used to determine the structure of various members of this solid solution. Unit-cell dimensions were seen to decrease as the Li content increased, in accord with the expected decrease in ionic size of Ti on oxidation, The Li channel and framework occupancy was seen t o follow a simple substitutional mechanism; for every two titanium atoms in the framework that are replaced by lithium atoms, one lithium is lost from the channel sites, introducing a channel vacancy site, The lithium tempera ture factors were seen to increase over a composition range from x = 0 to x = 0.143, This is probably related to the increased number of channel vacan cies, No evidence was observed for the splitting of the Li channel sites, e ven for the x = 0.143 end member. (C) 1998 Academic Press.