Optimization of the Synthesis and Compaction Modes of Ca3Co4O9 Oxide Composites with Multilayer Carbon Nanotubes

The Ca₃Co₄O₉ oxides are prepared by Pechini method and solid-phase methods. The compaction is performed by spark plasma sintering, cold pressing followed by explosive compression (explosion method), and by rapid hot pressing. The compaction achieved by the explosion method with the addition of an AlN binder provides the maximum thermoelectric figure of merit ZT_300 K = 0.161 at room temperature. Adding multilayer carbon nanotubes (CNTs) to the oxides prepared by the Pechini method deteriorates the characteristics, and increasing the CNT content in Ca₃Co₄O₉ prepared by the solid-phase method and compacted by rapid hot pressing increases the thermoelectric figure of merit ZT_300 K up to 0.048 in Ca₃Co₄O₉+3 wt.% CNT.