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High Ionic Conductor Member of Garnet‐Type Oxide Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12
Author(s) -
Kataoka Kunimitsu,
Akimoto Junji
Publication year - 2018
Publication title -
chemelectrochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.182
H-Index - 59
ISSN - 2196-0216
DOI - 10.1002/celc.201800679
Subject(s) - crystallography , octahedron , crystal structure , materials science , neutron diffraction , single crystal , lattice constant , ionic conductivity , analytical chemistry (journal) , diffraction , chemistry , physics , electrode , chromatography , electrolyte , optics
Abstract Single‐crystal rods of Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 were grown by floating zone melting. The typical size of the single‐crystal rod was 8 mm in diameter and 70 mm in length. Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 crystallizes in a cubic structure with an Ia ‐3 d space group and the lattice parameter a =12.9455 (6) Å. The crystal structure of Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 was refined to the conventional values of R =3.32 % and w R =4.45 % using single‐crystal X‐ray diffraction data, and to R =8.82 % and w R =7.45 % using single‐crystal neutron diffraction data. Li‐ions in the crystal structure occupied two crystallographic sites: the distorted tetrahedral 96 h site and the distorted octahedral 96 h site. Analyzing the results of AC impedance measurements, we estimated the total Li‐ion conductivity of member in Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 to be 1.27×10 −3 S cm −1 at 298 K. This value is the highest in the reported Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 members. Using NMR spectroscopy, we determined the Li diffusion coefficient to be 1.57×10 −13 m 2 s −1 at 298 K and 7.96×10 −13 m 2 s −1 at 333 K. These values related to Li‐ion migration are higher than those reported for polycrystalline samples.