Two–step processing of thermoelectric (Ca _0.9 Ag _0.1 ) ₃ Co ₄ O ₉ /nano–sized Ag composites with high ZT

A two–step processing method, spark plasma sintering (SPS) combined with a heat–treatment, was used to fabricate (Ca _0.9 Ag _0.1 ) ₃ Co ₄ O ₉ /nano–sized Ag composites. Sliver within the lattice generated hole carriers, and silver along the grain boundaries improved the transport path of the charge carriers. Samples sintered using SPS at different temperatures had very different thermoelectric properties. The results showed that when the sample was sintered at 1233 K, the maximum power factor reached 0.43 mW/(m·K ² ) along with an electrical resistivity of 8.61 mΩ·cm and a Seebeck coefficient of 196.90 μV/K, and the corresponding lattice thermal conductivity was 1.86 W/(m·K). This study shows how to improve the properties and broaden the application of Ca ₃ Co ₄ O ₉ thermoelectric ceramics.