Thermoelectric properties of p-type Fe 0.9Mn 0.1Si 2 with rare-earth oxide addition

Abstract

The effects of rare earth oxide dispersion on the thermoelectric properties of the Mn-doped p-type β-FeSi 2 (Fe 0.9Mn 0.1Si 2) were investigated. The Fe 0.9Mn 0.1Si 2 powders were mechanically alloyed with Y 2O 3 powder (0.5-4 mass%) and subsequently hot pressed. The added Y 2O 3 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 Y 2O 3 addition, which was caused by enhancing phonon scattering due to fine Y 2O 3 dispersion. It was also found that the added Y 2O 3 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 Y 2O 3 (0.5 and 1 mass%) was added. The improvement of the Seebeck coefficient could not be explained only by the fine dispersion of Y 2O 3 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 La 2O 3 powder. © 2005 The Thermoelectrics Society of Japan.