Reduced thermal conductivity in niobium-doped calcium-manganate compounds for thermoelectric applications

Abstract

Reduction of thermal conductivity is essential for obtaining high energy conversion efficiency in thermoelectric materials. We report on significant reduction of thermal conductivity in niobium-doped CaO(CaMnO3)m compounds for thermoelectric energy harvesting due to introduction of extra CaO-planes in the CaMnO3-base material. We measure the thermal conductivities of the different compounds applying the laser flash analysis at temperatures between 300 and 1000 K, and observe a remarkable reduction in thermal conductivity with increasing CaO-planar density, from a value of 3.7 W·m−1K−1 for m = ∞ down to 1.5 W·m−1K−1 for m = 1 at 400 K. This apparent correlation between thermal conductivity and CaO-planar density is elucidated in terms of boundary phonon scattering, providing us with a practical way to manipulate lattice thermal conductivity via microstructural modifications.