Improvement in thermoelectric properties of (ZnO)5In2O3 through partial substitution of yttrium for indium

We first measured the thermoelectric properties of layer-structured homologous compounds, (ZnO)(m)In2O3 (m = integer), and reported that they would become candidate materials for high-temperature thermoelectric energy conversion.(1-4) We further tried to improve their thermoelectric properties by partially substituting yttrium for indium in (ZnO)(5)In2O3. Though the ionic radius of Y3+ is larger than that of In3+, the a-axis (hexagonal system) elongated and c-axis shrank as Y was substituted for In. The thermoelectric properties were found to vary with a varying amount of Y substitution; 3% Y substitution gave rise to the largest thermoelectric figure of merit, i.e., 1.1-1.3 X 10(-4) K-1 at 960-1100 K. The abnormal change in the lattice structure by Y substitution was responsible for the unusual behavior of the thermoelectric properties.