Single crystal growth of homologous compounds in the ZnO-In2O3 system

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´ 10⁶Sm^-1 at room temperature, but it decreased with increasing temperature and attained a value of 5´ 10⁵Sm^-1at 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^-4Wm^-1K^-2 at 400 K. This factor decreased with temperature, and reached the value of 5.3´ 10^-5Wm^-1K^-2 at 1200 K.