Thermoelectric properties of the textured Bi_(1.9)Gd_(0.1)Te_3 compounds spark-plasma-sintered at various temperatures

摘要

Elemental composition, crystal and grain structures, specific electrical resistivity, Seebeck coefficient, thermal conductivity, and thermoelectric figure-of-merit of n-type grained Bi_(1.9)Gd_(0.1)Te_3 compounds, spark-plasma-sintered at T_s = 690, 720, 750, 780 and 810 K, have been studied. All the samples are highly textured along the 001 direction parallel to the pressing direction. The average grain size measured along the pressing direction is much less as compared to the average grain size measured in the perpendicular direction. A strong anisotropy in the transport properties measured along directions parallel and perpendicular to the pressing direction was found within the 290 ÷ 630 K interval. Electrical resistivity decreases and thermal conductivity increases for parallel orientation as compared to these properties for perpendicular orientation. The T_s - effect on thermoelectric figure-of-merit of textured Bi_(1.9)Gd_(0.1)Te_3 compounds has been found and analyzed. Highest thermoelectric figure-of-merit ( - 0.75) was observed for sample with T_s = 750 K at perpendicular orientation.