The Origin of Phase Transition and the Usual Evolutions of the Unit-Cell Constants of the NASICON Structures of the Solid Solution LiTi2 – xGex(PO4)3

Physics of the Solid State - Ge-doped LiTi2(PO4)3 has been synthesized by a conventional solid-state reaction. Compounds LiM$$_{2}^{{{\text{IV}}}}$$(PO4)3 with LTP-type structure present a...     

Structure, microstructure and ionic conductivity of the solid solution LiTi2−xSnx(PO4)3

The Nasicon compounds with the composition LiTi_2−xSn_x(PO₄)₃ (x=0-1.8) were synthesised by the solid state reaction. Their structures were determined from X-ray powder diffraction using Rietveld analysis. All the compositions present the space group R-3c. The refinements show that the Ti and Sn cations are statistically distributed over the same position while the Li ones are exclusively located on the M1 site. The lattice constants a and c exhibit linear variation over the whole composition range. The bond lengths are in accordance with those of other Nasicon structures. The SEM micrographs of the samples show relative porous microstructures. The ionic conductivity is about 10⁻⁴-10⁻⁵ S cm⁻¹; for the activation energy, a typical value of 0.32 eV is obtained for x=0.6 composition whereas significant deviation from linearity in the temperature dependence of the dc conductivity, is observed for the Sn-rich ones. This tendency is discussed along with the structural features.