Relationships between crystallite size and thermoelectric properties of nano-structured CrSi2 prepared by the reduction-diffusion and spark plasma sintering methods

Abstract

Nano-structured polycrystalline samples of chromium disilicide (CrSi2) were fabricated by the reduction-diffusion (RD) and spark plasma sintering (SPS) methods to investigate the dependence of electrical conductivity σ and lattice thermal conductivity κL on crystallite size. The mean crystallite sizes of each SPS-treated CrSi2 sample were clarified by the Williamson–Hall method and microstructure observations. The mean crystallite sizes were all less than 100 nm, and became smaller as the SPS temperature was decreased from 1073 to 873 K. Although σ was not strongly affected by the crystallite size, κL decreased as the mean crystallite size decreased. The maximum zT of 0.18 at 600 K was realized for the CrSi2 sample prepared by SPS at 873 K, which had a mean crystallite size of 46.2(5) nm. These results indicate that the RD and SPS methods are effective for decreasing κL in CrSi2.