Abstract
We report the synthesis, structure and ionic conductivity of new layered perovskite oxides of the formula $LiLnTiO_4$ (Ln=La, Nd). These oxides were synthesized from their sodium analogues, $NaLnTiO_4$, by ion-exchange using molten LiNO3. Determination of crystal structure by Rietveld analysis of powder X-ray diffraction data reveals that $LiLnTiO_4$ compounds crystallize in a tetragonal structure, P4/nmm space-group (a=3.7700(2) A, c=12.076(1) A for La compound; a=3.7465(3) A, c=11.895(5) A for Nd compound), related to the parent $NaLnTiO_4$. While the Na atoms in $NaLnTiO_4$ are 9-coordinated as in the $K_2NiF_4$ structure, the Li atoms in $LiLnTiO_4$ are 4-coordinated (tetrahedral); other structural features of $NaLnTiO_4$ are retained in $LiLnTiO_4$. $LiLnTiO_4$ oxides show moderate lithium-ion conductivity $(s\a10^{-4}-10^{-5} S.cm^{-1} at 780°C)$ that is higher by about two orders of magnitude than that of$Li_2La_2Ti_3O_10$
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