Thermoelectric Properties of p-Type Fe_0.9Mn_0.1Si₂ with Rare-Earth Oxide Addition

Abstract

The effects of rare earth oxide dispersion on the thermoelectric properties of the Mn-doped p-type β-FeSi₂ (Fe_0.9Mn_0.1Si₂) were investigated. The Fe_0.9Mn_0.1Si₂ powders were mechanically alloyed with Y₂O₃ powder (0.5–4 mass%) and subsequently hot pressed. The added Y₂O₃ was dispersed in the β phase matrix as a fine particles around 10 nm in size. The thermal conductivity of the sample was significantly reduced by Y₂O₃ addition, which was caused by enhancing phonon scattering due to fine Y₂O₃ dispersion. It was also found that the added Y₂O₃ was partially decomposed in the sample, resulted in solution of elemental Y in the β phase as a p-type dopant. The Seebeck coefficient was slightly improved when a small amount of Y₂O₃ (0.5 and 1 mass%) was added. The improvement of the Seebeck coefficient could not be explained only by the fine dispersion of Y₂O₃ and the Y doping as a p-type dopant. The slight increase in the Seebeck coefficient was also observed in the case of the samples with addition of small amounts of La₂O₃ powder.