Large thermoelectric power inNaCo2O4single crystals

Abstract

We measured and analyzed the transport properties of single-crystal ${\mathrm{NaCo}}_2{\mathrm{O}}_4$, which is a metallic transition-metal oxide consisting of a two-dimensional triangle lattice of Co. Reflecting the crystal structure, the resistivity is highly anisotropic between in- and out-of-plane directions, and the in-plane resistivity is as low as 200 $\mu \Omega$ cm at 300 K. Most strikingly, the in-plane thermoelectric power of ${\mathrm{NaCo}}_2{\mathrm{O}}_4$ is about 100 $\mu$V/K at 300 K, which is nearly ten times larger than that of typical metals. The large thermoelectric power and the low resistivity suggest that ${\mathrm{NaCo}}_2{\mathrm{O}}_4$ is a potential thermoelectric material.