Crystal Structure and Thermoelectric Properties of Al-containing Re Silicides

<jats:title>ABSTRACT</jats:title><jats:p>The microstructure, defect structure and thermoelectric properties of Al-containing ReSi<jats:sub>1.75</jats:sub> based silicides have been investigated. All the Al-containing alloys investigated contain four differently oriented domains accompanied by the twinned microstructure, as the binary alloy does. However, thin defect layers containing a kind of shear structure are locally and sporadically formed at some of twin boundaries. In the defect layer, shear occurs by the vector of [100] on either (<jats:overline>1</jats:overline> 09) or (107) planes. Binary ReSi<jats:sub>1.75</jats:sub> exhibits nice thermoelectric properties as exemplified by the high value of dimensionless figure of merit (ZT) of 0.70 at 800 °C when measured along [001], although the ZT value along [100] is just moderately high. Al-containing Re silicides considerably increase the ZT value along [100] so that the maximum value of 0.95 is achieved at 150 °C for the ReSi<jats:sub>1.75</jats:sub>Al<jats:sub>0.02</jats:sub> alloy. The temperature dependence of electrical resistivity changes from of semiconductor for the binary alloy to of metal for the Al-added alloys and the value of electrical resistivity is significantly reduced when compared to the binary counterpart.</jats:p>