Hidenori Hiramatsu

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 In 2 O 3 ( m = integer), and reported that they would becomecandidate 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 In 2 O 3 . Though the ionic radius of Y 3+ is larger than that of In 3+ , 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 × 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.