Synthesis and thermoelectric properties of Cr-substituted higher manganese silicides prepared by pack cementation

Abstract

Higher manganese silicides are attractive low-cost thermoelectric materials finding application in middle to high-temperature power generation. However, for practical use their performance needs to be enhanced. Pack cementation is a simple, green and economic method applied so far on the preparation of pure thermoelectric metal silicide powders. In this study, pack cementation is employed for the synthesis of doped thermoelectric powder for the first time as a promising single-step process. Compounds Mn1-xCrxSi1.80 (0.02≤x ≤ 0.15) at which Cr substitutes Mn site in the matrix are prepared and examined regarding their composition, microstructure and performance. Considerable amounts of CrSi2 impurity are present for x ≥ 0.07. The highest thermoelectric efficiency is achieved for Cr 4% substitution of Mn leading to the peak figure of merit ZTmax=0.59 at 814 K (∼35% enhancement). The measured oxidation resistance in this temperature region is high. Pack cementation has been successfully utilized to synthesize high-performance Cr-substituted higher manganese silicide powder.