Effect of Variation of Si Compositions on the Thermoelectric Properties of Al-added ReSi_(1.75) Single Crystals

摘要

The thermoelectric properties of ReSi_(1.73+x)Al_(0.02) (-0.02 < x < 0.04) have been investigated in the temperature range between 323 and 1073 K. As a result of Al-addition, the electrical properties of the ternary at low temperatures are changed from the character of nondegenerate semiconductors, which is of binary ReSii.75, to that of degenerate semiconductors, and the band-gap along [001] becomes wider than that of the binary. The variation of Si composition affects the electrical properties along [100], but those along [001] are conserved. The change of the band structure due to the variation of Si composition is estimated with the result of the Seebeck coefficient at low and high temperatures. The maximum dimensionless figure of merit (ZT) along [100] is about 0.7 in the temperature between 473 and 773 K and along [001] is 0.67 at 1073 K.