We report the measurements of thermopower, electrical resistivity and thermal conductivity in a complex cobalt oxide Li$_{ 0.48}$Na$_{ 0.35}$CoO$_{ 2}$, whose crystal structure can be viewed as an intergrowth of the O3 phase of Li$_{ x}$CoO$_{ 2}$ and the P2 phase of Na$_{ y}$CoO$_{ 2}$ along the c axis. The compound shows large room-temperature thermopower of $\sim$180 $\mu$V/K, which is substantially higher than those of Li$_{ x}$CoO$_{ 2}$ and Na$_{ y}$CoO$_{ 2}$. The figure of merit for the polycrystalline sample increases rapidly with increasing temperature, and it achieves nearly 10$^{ -4}$ K$^{ -1}$ at 300 K, suggesting that Li$_{ x}$Na$_{ y}$CoO$_{ 2}$ system is a promising candidate for thermoelectric applications.
Categories: cond-mat.mtrl-sci cond-mat.str-el