Synthesis and structure determination of reduced tantalates, Li₂LaTa₂O₇, Li₂Ca₂Ta₃O₁₀ and Na₂Ca₂Ta₃O₁₀, with a layered perovskite structure

New reduced tantalates, Li₂LaTa₂O₇, Li₂Ca₂Ta₃O₁₀ and Na₂Ca₂Ta₃O₁₀, with a layered perovskite structure have been synthesized by a chemical or an electrochemical intercalation reaction of the alkali metal cations with the parent Dion-Jacobson series compounds. The crystal structures of these compounds were determined by Rietveld analysis of powder X-ray diffraction patterns, and found to be analogous to those of the parent compounds. The intercalation of the lithium ion leads to a large contraction along the stacking direction of perovskite layers because of a higher interlayer charge density. These intercalation compounds are the first example of reduced tantalates with a layered perovskite structure.