Thermoelectric properties of Fe0.98Co0.02Si2 with ZrO2 and rare-earth oxide dispersion by mechanical alloying

Effects of Y<SUB>2</SUB>O<SUB>3</SUB> and Y Addition on Thermoelectric Properties of &beta;-FeSi<SUB>2</SUB> Synthesized by Mechanical Alloying and Hot Pressing

“…However, when dispersion of ZrO 2 , which comparably has a good chemical stability, by mechanical alloying (MA) was tried, ZrO 2 decomposed in the -FeSi 2 , resulting in deterioration of the thermoelectric performance. 19) This experimental result indicates that a dispersed second phase at least needs to be more stable than ZrO 2 . In the previous study, fine SiC particles around 20 nm in size were dispersed in the phase matrix by Si+C powder addition and mechanical alloying, and the thermal conductivity ( ph ) was reduced over the entire temperature range measured from 300 to 1100 K, resulting in significant improvement of the figure of merit.…”

“…On the other hand, it was reported that, when ZrO 2 with a relatively high chemical stability was added to the -FeSi 2 , the ZrO 2 phase decomposed and Zr atom was doped into the phase, resulting in the deterioration of the thermoelectric performance. 19) On the basis of this fact, it is expected that even when Y 2 O 3 is added, the Y 2 O 3 phase decomposes slightly and a small amount of Y atoms was dissolved in the phase. This Y solution may be associated with the enhancement of the Seebeck coefficient.…”

“…It has been reported that dispersion of rare earth oxides, which have low thermal conductivity and good chemical stability, was effective not only for reducing the thermal conductivity, but also for improving the Seebeck coefficient. 19) However, its microstructure (distribution of dispersed oxides in the phase matrix) and mechanism of improvement of the Seebeck coefficient have not been clarified yet. In the present study, Y 2 O 3 , as a rare-earth oxide, was dispersed in the typical ntype Co-doped -FeSi 2 (Fe 0:98 Co 0:02 Si 2 ) by mechanical alloying, and then the powder was sintered by using a hotpressing apparatus.…”

Thermoelectric Properties of p-Type Fe<SUB>0.9</SUB>Mn<SUB>0.1</SUB>Si<SUB>2</SUB> with Rare-Earth Oxide Addition

“…It was reported that when rare-earth oxides, such as Y 2 O 3 etc., were added to the Co-doped n-type -FeSi 2 (Fe 0:98 -Co 0:02 Si 2 ) synthesized by mechanical alloying and hot pressing, small rare earth particles around 10 nm in size were dispersed in the phase matrix, resulting in significant reduction in the thermal conductivity due to enhancement of phonon scattering. 18,19) Besides that, it was also found that the fine dispersion of rare-earth oxides was effective for improving the Seebeck coefficient. For example, Fig.…”

Thermoelectric properties of hot-pressed β-FeSi2 with yttria dispersion by mechanical alloying

“…Generally, it is considered that second phase dispersion in the ␤ phase matrix is effective for reducing the thermal conductivity due to enhancing phonon scattering. However, when dispersion of ZrO 2 , which comparably has a good chemical stability by mechanical alloying (MA), was tried; ZrO 2 decomposed in the ␤-FeSi 2 , resulting in deterioration of the thermoelectric performance [8]. This experimental result indicates that a dispersed second phase at least needs to be more stable than ZrO 2 .…”