The Li<sup>+</sup> ion conductor Li<sub>0.3</sub>La<sub>0.567</sub>TiO <sub>3</sub> was synthesized as a metastable phase quenched in liquid N <sub>2</sub> from 1300°C, and it was studied by time-of-flight powder neutron diffraction at high-resolution (HRPD instrument, ISIS Facility, U.K.). At room temperature a tetragonal perovskite superstructure was found, with a √2a<sub>p</sub> × √2a<sub>p</sub> × 2a<sub>p</sub> unit cell (a = 5.48027(1), c = 7.75591(2) Å, and Z = 4), I4/mcm space group, and a<sup>0</sup>a<sup>0</sup>c<sup>-</sup> tilt system of the TiO<sub>6</sub> octahedra. Superlattice hkl reflections with odd l were systematically weaker and broader. By Fourier difference maps, the Li atom was located in a disordered position inside the La vacancy hollow, close to the bottleneck site at the center of the Ti<sub>4</sub>O<sub>4</sub> square window. The Rietveld refinement converged to R<sub>p</sub> = 6.56%, R<sub>Bragg</sub>(even l) = 3.26%, and R<sub>Bragg</sub>(odd l) = 11.6%. A two-dimensional pathway of Li<sup>+</sup> ion mobility inside the structure, based on the coupled ordering of lithium and lanthanum, is proposed. At about 600°C the unit cell transforms into a <sub>p</sub> × a<sub>p</sub> × a<sub>p</sub>, with a disappearance of superlattice reflections. A tetragonal pseudo-cubic P4/mmm structure (a = 3.89644(1), c = 3.89748(2) Å, and Z = 1) was found (T = 650°C) and Rietveld refined to R<sub>p</sub> = 6.10% and R<sub>B</sub> = 4.86%. Lithium was located on the layer of Ti atoms rather than on that of La as in the room-temperature structure. © 2006 American Chemical Society.
Sommariva, M., Catti, M. (2006). Neutron diffraction study of quenched Li0.3La0.567TiO3 lithium ion conducting perowskite. CHEMISTRY OF MATERIALS, 18(9), 2411-2417 [10.1021/cm060120r].
Neutron diffraction study of quenched Li0.3La0.567TiO3 lithium ion conducting perowskite
CATTI, MICHELE
2006
Abstract
The Li+ ion conductor Li0.3La0.567TiO 3 was synthesized as a metastable phase quenched in liquid N 2 from 1300°C, and it was studied by time-of-flight powder neutron diffraction at high-resolution (HRPD instrument, ISIS Facility, U.K.). At room temperature a tetragonal perovskite superstructure was found, with a √2ap × √2ap × 2ap unit cell (a = 5.48027(1), c = 7.75591(2) Å, and Z = 4), I4/mcm space group, and a0a0c- tilt system of the TiO6 octahedra. Superlattice hkl reflections with odd l were systematically weaker and broader. By Fourier difference maps, the Li atom was located in a disordered position inside the La vacancy hollow, close to the bottleneck site at the center of the Ti4O4 square window. The Rietveld refinement converged to Rp = 6.56%, RBragg(even l) = 3.26%, and RBragg(odd l) = 11.6%. A two-dimensional pathway of Li+ ion mobility inside the structure, based on the coupled ordering of lithium and lanthanum, is proposed. At about 600°C the unit cell transforms into a p × ap × ap, with a disappearance of superlattice reflections. A tetragonal pseudo-cubic P4/mmm structure (a = 3.89644(1), c = 3.89748(2) Å, and Z = 1) was found (T = 650°C) and Rietveld refined to Rp = 6.10% and RB = 4.86%. Lithium was located on the layer of Ti atoms rather than on that of La as in the room-temperature structure. © 2006 American Chemical Society.
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