Enhanced Thermoelectric Properties of n-Type Bi₂Te_{3- x}Se _x Alloys following Melt-Spinning

Low-temperatures heat to electricity conversion technologies have gained an interest in recent years for utilizing a low-grade waste heat, such as that developed in the human body, the automotive and industrial sectors, and even in photovoltaic cells subjected to an intense solar radiation, into useful electricity. Such energy conversion can be obtained by thermoelectric devices. The most efficient thermoelectric compositions at temperatures lower than 300 °C are the p-type Bi_xSb_2-xTe₃ and n-type Bi₂Te_xSe_3-x bismuth telluride-based alloys. Yet, to date, higher conversion efficiencies were associated with the p-type alloys, leaving an unfulfilled potential of n-type Bi₂Te_xSe_3-x. In the current research, synthesis optimization procedures of n-type Bi₂Te_2.4Se_0.6 by combining the melt-spinning approach, capable of retaining some of the preferred crystallographic orientation, as required for electronic optimization, with hot-pressing, are reported. A high figure of merit, ZT, value of ∼1.07 at a temperature of ∼65 °C was obtained parallel to the pressing direction, at a wheel-spinning frequency of 300 rpm, which was attributed to the ∼50% maintained anisotropy of the inherent crystallographic structure.