Ionic conduction path, covalent bonding and phase transition of lithium-ion conductors

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We have reported the results of a neutron powder diffraction study of La_<0.62>Li_<0.16>TiO_3 perovskite that determines the diffusion path of lithium cations at room temperature. At 77K, the Li cations are located at the 2c site on the (002) La deficient layer, while at room temperature, they spread over a wide area and migrate following the 2c-4f-2c or 2c-2d-2c tie line. We have demonstrated that the probability density of Li cations has a minimum between the 2c and 4f or between the 2c and 2d positions on the diffusion path, in contrast to the previous reports where the bottleneck has been thought to be located at the 2c, 2d and 4f positions. Since most of the Li cations are not located at the 4j A-site but at the 2c site, the chemical formula of the title compound is not (La_<2/3-x>, Li_<3x>, (Va_<(A-site)>)_<1/3-2x>)_<A-site>TiO_3, but (La_<2/3-x>,(Va_<(A-site)>)_<1/3+x>)_<A-site>(Li_<3x>,(Va_<(2c)>)_<1/4-3x>)_<2c>TiO_3. The present conclusion would be helpful when discussing the … More conduction mechanism of Li-ion conductors.A size effect on crystal structure has been investigated for barium titanate (BaTiO_3) nanoparticles of 40-, 140- and 430-run sizes, by means of neutron and high-resolution synchrotron X-ray powder diffraction and Raman scattering techniques. Temperature dependence of lattice parameters of bismuth sesquioxide (Bi_2O_3) has been obtained between 26°and 778℃ by the Rietveld method using neutron powder diffraction data. A new electric furnace has been designed and fabricated for measurements of the high-resolution synchrotron radiation powder diffraction profiles from materials at high temperatures up to 1807 K in air, suitable for the multiple-detector system installed at the BL-4B_2 experimental station of the Photon Factory in Tsukuba, Japan. Crystal structure of copper iodide (CuI) has been studied at 300 K and 760 K using synchrotron X-ray powder diffraction data. Tantalum oxynitride (TaON) is investigated by neutron and synchrotron diffraction analysis to clarify the structural and electronic features responsible for the visible-light activity of this material. Less