Protective enamel coating for n- and p-type skutterudite thermoelectric materials

Transitioning skutterudite (SKD) thermoelectric technology from space to terrestrial power generation requires oxidation suppression technology. One approach involves the development of protective coatings consisting of the following properties: (i) low thermal conductivity to prevent parasitic heat loss, (ii) low electrical conductivity to prevent short-circuiting, (iii) coefficient(s) of thermal expansion matching that of the thermoelectric material, and (iv) adequate thermal stability and mechanical strength for durability. In this work, n-type Ba0.05Yb0.025CoSb3 and p-type Ce0.9Co0.5Fe3.5Sb12 were coated with a silica-based enamel to prevent their oxidation. This work demonstrates the efficacy of enamel coatings for suppressing oxidation of n-type SKD, and for the first time, p-type SKD in static and thermal cyclic heating tests up to 600 °C in air. The coating process, physical characterization of the enamel, and materials characterization data are presented and discussed.