抄録
Polycrystalline Ca3-xLnxCo4O9 (x < 0.5) samples with Ln = Dy, Ho, Er and Lu for x < 0.5 were prepared using hot-pressing (HP) technique and investigate the influence of rare-earth substitution for Ca on their thermoelectric properties and microstructure. With the Ln substitution, high-temperature thermopower increases and both the thermal and electrical conductivities decrease. However, the decrease in the electrical conductivity is more substantial in low temperature region (T < 600 K) than that in higher temperature region. High-temperature thermoelectric figure-of-merit is significantly improved by the Ho and Lu substitutions, particularly those for the Lu-doped samples. From scanning electron microscope (SEM) observation, sheet-like grains are thinner and smaller in size for the Ln-doped samples than those for non-doped one.
