Thermoelectric transportation in Cu-added Ca3Co4O9 ceramics consolidated by spark plasma sintering

During the last decade, misfit layered calcium cobaltite (Ca3Co4O9) has appeared as a potential candidate for oxide thermoelectric materials. In the present work, we report improved thermoelectric properties of Ca3Co4O9 through a facile synthesis route. Ca3Co4O9 based composites have been prepared by mixing different wt. % of Cu using ball-milling. The pure and composite powdered samples have been consolidated into bulk ceramics by spark plasma sintering (SPS). The detailed structural investigations reveal a multiphase system comprising of Cu, Ca3Co4O9, Ca3Co4-xCuxO9 and a minority phase of Co3O4. The simultaneous improvement in the electrical conductivity and Seebeck coefficient results in an improved power factor and the highest value of 384 μW/m.K2 at 973K have been obtained for the sample containing 5% Cu by wt. The conduction mechanisms have been discussed in detail to investigate the reasons associated with the improved thermoelectric properties.