Thermal conductivity and dimensionless figure of merit of thermoelectric rhodium oxides measured by a modified harman method

We have developed a modified Harman method to extract the thermoelectric signal using a squared AC current in the presence of Joule heating, and have measured the thermal conductivity and dimensionless figure of merit of single crystals of the layered rhodium oxide Bi _0.78Sr _0.4RhO _3+d and the pseudo-one-dimensional rhodium oxide Ba _1.2Rh ₈O ₁₆. We find that these rhodium oxides exhibit a small thermal conductivity of 30 mW/cm K at 200 K and rather large ZT of 0.02 below 200 K. We believe that this method will be a powerful tool for thermal conductivity measurements in sub-millimeter-sized crystals.