CrSi₂熱電材料におけるp型挙動の由来とAlドーピングが出力因子に与える影響

抄録

Chromium disilicide (CrSi₂) is generally known as a p-type degenerate semiconductor whose power factor can be improved by substitution of Al on the Si site. However, it has not been clarified why holes are majority carriers in pure CrSi₂ nor how the thermoelectric properties of CrSi_2−xAl_x depend on the temperature above 400 °C. In this paper, we prepared CrSi_2−xAl_x samples with x ranging from 0.00 to 0.20. The composition ratio in each sample measured by Wavelength-dispersive X-ray spectroscopy (WDX) showed that the sum of Si and Al to Cr was less than the stoichiometric ratio. The electronic density of states calculated by first principles calculation based on density functional theory revealed that the atomic vacancies on the Si sites, whose existence was implied by WDX, can supply holes. Comparing thermoelectric properties of the samples at 500 °C, the sample with nominal composition CrSi_1.96Al_0.04 showed the highest power factor 0.606 mW m⁻¹ K⁻².