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

Single crystals of (ZnO)₅In₂O₃ were grown by a normal flux method, using PbF₂ as a flux, and the resulting flaky single crystals were very thin along the c-axis. Single crystal quality was evaluated by XRD, TEM, and SEM. Band gap energy of single crystal was optically determined. The inplane electrical conductivity (σ), and Seebeck coefficient (cc) were measured in the temperature range of 300 K to 1200 K and 500 K to 1200 K in air, respectively. The electrical conductivity of a single crystal was found to be 2×10⁶ Sm^-1 at room temperature, it decreased with increasing temperature and attained a value of 5×10⁵ Sm^-1 at 1200 K. Anisotropy of two orders of magnitude in electrical conductivity was first clarified. Seebeck coefficient was determined to be -9.6 μVK^-1 at 500 K and -31.6 μVK^-1 at 1200 K. The estimated power factor was about 1.4×10^-4 Wm^-1K^-2 at 500 K. This factor increased with temperature, and reached the value of 5.3×10^-4 Wm^-1K^-2 at 1200 K.