Structural, spectroscopic and electrical features of undoped and Mn-doped LiTi2(PO4)3

The study of the ionic conducting material LiTi2(PO 4)3 and of its Mn-substituted derivate reveals that the Mn distribution is strictly related to the synthetic method. The results of the structural refinement of X-ray and neutron (ToF) powder diffraction data and of XPS analysis demonstrate that Mn2+ ions are located on the lithium octahedral site, while Mn3+ and Mn4+ ions occupy the titanium ones. The Mn2+ amount on the lithium site seems to be the main factor responsible for the conductivity decrease observed in doped samples. The EPR spectra evidence clustering effects of Mn on both Li and Ti sites and the presence of more insulated Mn2+ ions. The effect of the major Mn amount on Ti site in the case of the sol-gel synthesis is consistent with the different EPR line shape of the related sample. The neutron diffraction and 7Li MAS NMR results do reveal that lithium occupies the M1 site of the rhombohedral LiTi2(PO4)3 structure.