Thermoelectric properties of layered Ca3.95RE0.05Mn3O10 compounds (RE=Ce, Nd, Sm, Eu, Gd, Dy)
Résumé
In this work, polycrystalline samples of the substituted n = 3 Ruddlesden-Popper Ca4−xRExMn3O10 phase were prepared by solid-state reaction (RE, rare earth = Ce, Nd, Sm, Eu, Gd, Dy). Single phased samples were synthesized for sintering times larger than 150 h at 1350 °C. Complete thermoelectric characterizations were performed from 5 to 390 K, in terms of electrical resistivity (ρ), Seebeck coefficient (S) and thermal conductivity (κ). As expected, the substitution of Ca by different rare earth elements leads to a significant modification of the thermoelectric properties. With substitution level as low as 1.25 at.%, a remarkable decrease of the electrical resistivity is observed. The influence of this cationic substitution on the thermal conductivity (κ), Seebeck coefficient (S), and the figure of merit ZT is also discussed. In this study, the best one reaches 5.8 × 10−3 at 300 K for the Ca3.95Eu0.05Mn3O10 composition, a value 6 times higher than the ZT exhibited by the beginning Ca4Mn3O10 sample.