Thermoelectric performance of textured Ca3−xYbxCo4O9−δ ceramics

A series of ceramics Ca3−xYbxCo4O9−δ (x = 0, 0.2, 0.3, 0.4, 0.5) were prepared by the sol–gel method followed by pressing and sintering. The thermoelectric properties were characterized from room temperature to 870 K. Partial Yb3+ ions substituting for Ca2+ sites enter into the lattices without any impurity phase, and form highly textured structure. Ca3−xYbxCo4O9−δ samples exhibit semiconducting behavior and the Seebeck coefficient increase strikingly by increasing the content of Yb3+ ion. The thermal conductivity varies within narrow limits, and the figure of merit ZT of Ca2.8Yb0.2Co4O9−δ exceeds 0.16 at 870 K.