Structural features responsible for lithium conductivity in Li 1+x Ti 2−x Al x (PO 4 ) 3 (x = 0, 0.2, and 0.4) samples have been investigated by Rietveld analysis of high-resolution neutron diffraction (ND) patterns. From structural analysis, variation of the Li site occupancies and atomic thermal factors have been deduced as a function of aluminum doping in the temperature range 100−500 K. Fourier map differences deduced from ND patterns revealed that Li ions occupy M1 sites and, to a lower extent, M3 sites, disposed around ternary axes. The occupation of M1 sites by Li ions is responsible for the preferential expansion of the rhombohedral R3̅ c unit cell along the c axis with temperature. The occupation of less symmetric M3 sites decreases electrostatic repulsions among Li cations, favoring ion conductivity in Li 1+x Ti 2−x Al x (PO 4 ) 3 compounds. The variations detected on long-range lithium motions have been related to variations of the oxygen thermal factors with temperature. The information deduced by ND explains two lithium motion regimes deduced previously by 7 Li NMR and impedance spectroscopy.Article pubs.acs.org/IC
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.