Low temperature thermopower and electrical transport in misfit Ca(3)Co(4)O(9) with elongated c-axis

Abstract

The temperature dependence of the electrical resistivity (rho) and thermopower (S) of misfit cobaltite Ca(3)Co(4)O(9) has been studied. The compound is a promising thermoelectric material, exhibiting very low rho (similar to 1.3 x 10(-4) Omega cm) and reasonably high S (similar to 56 mu V K(-1)) at room temperature, which is desirable for thermoelectric applications. At T < 80 K, S exhibits T(3/2) dependence, suggesting that electron-magnon scattering has a pronounced influence on S at low temperatures. Ca(3)Co(4)O(9) exhibits a temperature independent power factor in the temperature range 300-80 K. A comparison of the temperature dependence of the power factor of Ca(3)Co(4)O(9) with various materials projected or used as a thermoelectric cooler (e.g. single crystal of short c-axis Ca(3)Co(4)O(9), polycrystalline La(0.95)Sr(0.05)CoO(3), Bi(0.85) Sb(0.15), Bi(2)Te(3), Bi-SiO(2) composite) indicates that title compound Ca(3)Co(4)O(9) is a much superior candidate for thermoelectric applications.