Triple-phase ceramic 2D nanocomposite with enhanced thermoelectric properties

A thermoelectric triple-phase p-type Ca3Co4O9-NaxCoO2-Bi2Ca2Co2O9 (CCO-NCO-BCCO) 2D nanocomposite was obtained from pressureless sintering in air. The anisotropic thermoelectric properties of the nanocomposite exhibit a high electrical conductivity of 116 S cm(-1) and a power factor of 6.5 mu W cm(-1) K-2 perpendicular to the pressing direction at 1073 K in air. A corresponding zT value of 0.35 was obtained. Three co-doped, thermoelectrically active misfit-layered materials were stacked to form a triple-phase nanocomposite, which combines the advantages of all three materials. The resulting nanocomposite enables simultaneous increases of the isothermal electrical conductivity a and the Seebeck coefficient a by charge carrier concentration engineering and synergistic effects. The Bi2Ca2Co2O9 and NaxCoO2 phases were stabilized in a Ca3Co4O9 matrix at high temperatures. To evaluate the application of the nanocomposite in high-temperature thermoelectric generators, the representation of the electrical conductivity and power factor in a loffe plot was more appropriate than the zT value.