Electrochemical Intercalation of Lithium into Layered Niobates ACa₂Nb₃O₁₀(A=K, Rb, Cs)

Abstract

We prepared Li-intercalated layered niobium oxide Li_xACa₂Nb₃O₁₀(A=K, Rb, Cs) by an electrochemical technique. The host compounds ACa₂Nb₃O₁₀ were synthesized by a solid state reaction method at 850-1150°C for 10-12h. Each of the cyclic voltammograms of these compounds had one cathodic peak at--3V, indicating that the Li-intercaration occurred at this voltage. All of the intercalated compounds Li_xACa₂Nb₃O₁₀ (A=K, Rb, Cs) showed superconductivity at 4-5K, and their x-ray diffraction pattern remained almost unchanged in spite of the Li-intercalation. For Li_xRbCa₂Nb₃O₁₀, no superconductivity appeared up to x = 0.17, for x=0.34 and 0.46 Tc (determined as the onset of the Missner effect) was constant at 4 K, and for x = 0.62 Tc decreased slightly to 3K.