High Thermoelectric Figure of Merit of p-Type Ternary Unfilled Skutterudite FeSb2Te via Ge Doping

Point defect scattering is supposed to be as an efficient means of decreasing the lattice thermal conductivity. In this study, single phase Ge-substituted FeSb(2)GexTe(1-x) (x = 0 similar to 0.2) compounds were successfully prepared by a traditional melting-annealing combined with subsequent spark plasma sintering technique. Ge-substitution, by effectively increasing hole concentration, significantly increases the electrical conductivity while retaining a high Seebeck coefficient due to the large density of state of valence band, which gives rise to a large power factor. Concurrently, through introducing effective point defects scattering to heat-carrying phonons, Ge-substitution considerably decreases the lattice thermal conductivity which is comparable with those of filled skutterudites. As a consequence, Ge-substitution efficiently improves the thermoelectric figure of merit with a maximum value reaching similar to 0.5 at 750 K for the x=0.1 sample.