Enhancement of thermoelectric performance in n-type PbTe[subscript 1−y]Se[subscript y] by doping Cr and tuning Te:Se ratio

Abstract

Lead telluride and its alloys have been extensively studied for medium temperature thermoelectric applications due to decent figure-of-merit (ZT) at temperature close to 900 K. However, little emphasis has been given to improve the ZT near room temperature. In this investigation, we report a systematic study of Cr doping in PbTe[subscript 1−y]Se[subscript y] with y=0, 0.25, 0.5, 0.75, 0.85, and 1. We found the peak ZT temperature increased with increasing concentration of Se. The highest ZT of ~0.6 at room temperature in Te-rich Cr[subscript 0.015]Pb[subscript 0.985]Te[subscript 0.75]Se[subscript 0.25] was obtained due to a lowered thermal conductivity and enhanced power factor resulted from high Seebeck coefficient of about −220 µV K[superscript −1] and high Hall mobility ~1120 cm[superscript 2] V[superscript −1] s[superscript −1] at room temperature. A room temperature ZT of ~0.5 and peak ZT of ~1 at about 573–673 K is shown by Se-rich sample Cr[subscript 0.01]Pb[subscript 0.99]Te[subscript 0.25]Se[subscript 0.75]. This improvement of the room temperature ZT improved the average ZT over a wide temperature range and could potentially lead to a single leg efficiency of thermoelectric conversion for Te-rich Cr[subscript 0.015]Pb[subscript 0.985]Te[subscript 0.75]Se[subscript 0.25] up to ~11% and Se-rich Cr[subscript 0.01]Pb[subscript 0.99]Te[subscript 0.25]Se[subscript 0.75] up to ~13% with cold side and hot side temperature at 300 K and 873 K, respectively, if matched with appropriate p-type legs.