ICT2014 Abstracts

Here we report thermoelectric study of crossroads material MnTe via iso-electronic doping S on the Te-site). MnTe_1-xS_x samples with nominal S content of x = 0.00, 0.05 and 0.10 were prepared using a melt-quench method followed by pulverization and spark plasma sintering. The X-ray powder diffraction, scanning electron microscopy, and ZAF-corrected compositional analysis confirmed that S uniformly substitutes Te up to slightly over 2%. A higher content of S in the starting materials led to the formation of secondary phases. The thermoelectric properties of MnTe_1-xS_x samples were characterized by means of Seebeck coefficient, electrical conductivity, and thermal conductivity measurements from 300 K to 773 K. Furthermore, Hall coefficient measurements and a single parabolic band model were used to help gain insights on the effects of S-doping on the scattering mechanism and the carrier effective mass. As expected, S doping not only introduced hole charge carriers but also created short-range defects that effectively scatter heat-carrying phonons at elevated temperatures. On the other hand, we found that S doping degraded the effective mass. As a result, the ZT of MnTe_0.9S_0.1 was substantially enhanced over the pristine sample near 400 K while the improvement of ZT became marginal at elevated temperatures. A ZT ~ 0.65 at 773 K was obtained in all three samples.