Figure 7
Experimental thermoelectric property measurements and enhancement in the thermoelectric performance with respect to the doping content of Ga Enhancements in transport coefficients (shown by colored area plots) with respect to temperature for doping of 1, 3 and 5% Ga. (a) Electrical conductivity (σ) (d) Seebeck coefficient/thermopower (S) (e) Power factor (PF) S2σ (f) thermoelectric figure of merit ZT. The absence of colored area regions for a particular plot (doping) essentially represents zero enhancement in that zone of temperature. Incremental Integrated enhancement over 300–600 K as function of Ga atomic % doping content for (e) Electrical conductivity (σ) (f) Seebeck coefficient/thermopower (S) (g) Power factor (PF) S2σ (h) thermoelectric figure of merit ZT. Ga doping (3 and 5%) enhanced both electrical transport (σ, S) & heat transport (κ) coefficients. In addition, better power factor was achieved after doping at medium temperatures. However, the TE efficiency is inversely related to κ, thus Ga doping above a certain limit (~5%) degraded the thermoelectric performance. Due to the optimized combinations of a large σ (6 × 10 5S/m), highest S (70 μV/K) and moderate κ (3.1364 W/K-m), highest enhancement in thermoelectric performance was observed in Cu1.97Ga0.03Te (ZT = 0.46 at 600 K), higher than state of the art TE materials for medium temperature applications.
