Enhanced thermoelectric properties of Ca3Co4O9 by adding nano MoSi2

Abstract

Adding nanoparticles is a method to regulate the performance of thermoelectric materials. Ca3Co4O9/x MoSi2 (x = 0, 0.05, 0.10, 0.13, and 0.16) was synthesized by a wet chemical method combined with atmospheric pressure sintering. The XRD and SEM results reveal that there are no other reaction in the samples. The grain size of all samples decrease with increasing MoSi2 content, and all presented a similar flake morphology. The influence of MoSi2 on the thermoelectric performance of Ca3Co4O9 is systematically analysed. The appropriate addition of nano-MoSi2 particles can increase the carrier concentration and enhance conductivity of Ca3Co4O9. The electrical conductivity of Ca3Co4O9/0.05 MoSi2 is 83.16 Scm−1, which is 49.2% higher than that of Ca3Co4O9 at 1080 K. The Seebeck coefficient of the Ca3Co4O9/0.16 MoSi2 sample reaches 197.56 μVK−1 at 980 K, which is significantly better than that of previously reported samples prepared by the same method. Moreover, combined with the experimental results and the analysis of the effective medium theory model, the addition of MoSi2 can effectively debase the thermal conductivity of Ca3Co4O9. The thermal conductivity of Ca3Co4O9/0.16 MoSi2 (∼1.26 Wm−1K−1, 1080 K) samples decrease greatly, which is attributed to the influence of interfacial thermal resistance and pores in the Ca3Co4O9/MoSi2. The ZT value of the Ca3Co4O9/0.05 MoSi2 sample increases by 44.4% compare with that of Ca3Co4O9 and reaches 0.26 at 1080 K. These results demonstrate that adding an appropriate amount of MoSi2 particles is one of the methods to enhance the thermoelectric performance of Ca3Co4O9 ceramic samples.