Single crystal growth of homologous compounds in the ZnO-In2O3 system and their thermoelectric properties

O. Malochkin, K. Koumoto

Department of Applied Chemistry, Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan

This is the first report on the thermoelectric properties of (ZnO)5In2O3 single crystal. The single crystals of (ZnO)5In2O3 were grown by normal flux method, and the resulting flaky single crystals were very thin along the c-axis. Single crystal quality was evaluated by X-ray diffraction (XRD), TEM, SEM and EDAX. The in-plane electrical conductivity (s ), and Seebeck coefficient (a ) were measured in the temperature range of 300 K to 1200 K in air. The electrical conductivity of a single crystal was found to be 2´ 106 Sm-1 at room temperature, but it decreased with increasing temperature and attained a value of 5´ 105 Sm-1 at 1200 K. Seebeck coefficient was determined to be -9.6 m VK-1 at 400 K and -31.6 m VK-1 at 1200 K. Seebeck coefficients were always negative, and the single crystal specimens were n-type semiconductors. The absolute value of the Seebeck coefficient increased with increasing temperature. The estimated power factor (PF=s ´ a 2) was about 1.4´ 10-4 Wm-1K-2 at 400 K. This factor decreased with temperature, and reached the value of 5.3´ 10-5 Wm-1K-2 at 1200 K.