Low-Temperature Synthesis and Electric Properties of New Layered Cobaltite, SrxCoO2

Abstract

A new layered strontium cobaltite, SrxCoO2, was synthesized by a low-temperature ion-exchange technique from a γ-Na0.7CoO2 precursor. The strontium content was determined to be x = 0.345 by inductively coupled plasma (ICP) analysis. Rietveld analysis of X-ray powder diffraction data indicates that strontium ions are preferentially distributed at the 2d (2/3, 1/3, 1/4) site (space group P63/mmc). The chemical content of strontium ions was determined as x = 0.346(3) relative to cobalt ions. A polycrystalline sample of Sr0.35CoO2 shows metallic electric resistivity below 300 K. The Seebeck coefficient is about 70 µV·K-1 at 300 K, which is comparable to that of γ-Na0.7CoO2.