Skutterudite Thermoelectric Modules with High Volume-Power-Density: Scalability and Reproducibility

Abstract

The construction and evaluation of wholly skutterudite thermoelectric modules with a high volume-power-density is described. Such modules afford the maximum power output for the minimum use of material. Synthesis of the component n-type unfilled skutterudite CoSb2.75Sn0.05Te0.20 and p-type filled skutterudite Ce0.5Yb0.5Fe3.25Co0.75Sb12 was achieved using a scalable ball-milling route that provides sufficient material for the construction and assessment of performance of 12 modules. Impedance spectroscopy at room temperature is shown to provide a rapid means of evaluating the quality of module fabrication. The results show a high degree of reproducibility in module performance across the 12 modules, with an average internal resistance of 102(4) mΩ. Electrical measurements on the component n- and p-type materials reveal power factors (S2/ρ) of 1.92 and 1.33 mW m–1 K–2, respectively, at room temperature and maximum figures of merit of ZT = 1.13 (n-type) and ZT = 0.91 (p-type) at 673 and 823 K, respectively. The figure of merit of the module at room temperature (ZT = 0.12) is reduced by ca. 39% from the average of the n- and p-type component materials at the same temperature, as a result of thermal- and electrical-contact resistance losses associated with the architecture of the module. I–V curves for the module determined for ΔT in the range 50–450 K show an almost linear dependence of the open-circuit voltage on ΔT and allow calculation of the power output, which reaches a maximum value of 1.8 W (0.9 W cm–2) at ΔT = 448 K.