Synthesis and Lithium-Ion Conductivity of LiSrB₂O₆F (B= Nb⁵⁺, Ta⁵⁺) with a Pyrochlore Structure

摘要: This study investigated the conductivity of lithium ions in new pyrochlore materials. A two-step synthesis method, comprising a simple solid-state reaction followed by a high-pressure solid-state reaction was used to synthesize single-phase undoped LiSrB 2 O 6 F (where B= Nb 5+ or Ta 5+). The samples were doped with the lower valent cation, Zr 4+, which replaced Nb 5+ or Ta 5+ at B-sites in LiSrB 2 O 6 F and similarly, A-site point defects were introduced by reducing the amount of Sr in the sample. The crystal structure was determined by Rietveld analysis of the X-ray synchrotron diffraction data. Ionic conductivities of the samples were evaluated using electrochemical impedance spectroscopy. Sr 2+ deficient samples showed better conductivity (8.21× 10− 6 S cm− 1 for Nb-containing samples and 6.38× 10− 6 S cm− 1 for Ta-containing samples at 300 C) than that of Zr 4+-doped samples (5.58× 10− 6 S cm− 1 for Nb-containing samples and 3.58× 10− 6 S cm− 1 for Ta-containing samples at 300 C).