Functionally Graded (PbTe)1–x(SnTe)x Thermoelectrics

Functionally graded (PbTe)1–x(SnTe)x ingots have been prepared by Bridgman crystal growth method for the first time. From SEM-EDX, the composition (x) of the ingot was found to increase smoothly from 10.6 to 25.4 along the direction of the growth. The gradual change in composition is shown to cause a decrease in band gap as crystallization proceeds, and to be accompanied by a change in carrier concentration. By a Potential-Seebeck microprobe (PSM), a smoothly varying Seebeck coefficient was measured along the growth direction of the sample at room temperature. High-temperature properties relevant for thermoelectric performance were measured and used to evaluate the potential of this system as a functionally graded high-temperature thermoelectric material. This study provides insight into understanding the complicated interplays of advanced crystal growth and physical properties, going beyond standard thermoelectric sample preparation approaches.