Optimized thermoelectric properties of Mo3Sb7-xTex with significant phonon scattering by electrons

Heavily doped compounds Mo3Sb7 Te-x(x) (x = 0, 1.0, 1.4, 1.8) were synthesized by solid state reaction and sintered by spark plasma sintering. Both X-ray diffraction and electron probe microanalysis indicated the maximum solubility of Te was around x = 1.8. The trends in the electrical transport properties can generally be understood using a single parabolic band model, which predicts that the extremely high carrier concentration of Mo3Sb7 (similar to 10(22) cm(-3)) can be reduced to a nearly optimized level (similar to 2 x 10(21) cm(-3)) for thermoelectric figure of merit (zT) by Te-substitution with x = 1.8. The increased lattice thermal conductivity by Te-doping was found to be due to the decreased Umklapp and electron-phonon scattering, according to a Debye model fitting. The thermoelectric figure of merit (zT) monotonously increased with increasing temperature and reached its highest value of about 0.51 at 850 K for the sample with x = 1.8, making these materials competitive with the state-of-the-art thermoelectric SiGe alloys. Evidence of significant electron-phonon scattering is found in the thermal conductivity.