Effects of Re substitution for Mn on microstructures and properties in Re-substituted higher manganese silicide thermoelectric material

Effects of Re substitution for Mn on the microstructure-property relationships in Mn30.4Re6.0Si63.6 thermoelectric material have been investigated in comparison with those in Mn36.4Si63.6. The rapid quenching using the meld spinning leads to relatively uniform distribution of Re. After sintering, the Nowotny chimney ladder phases known as the higher manganese silicide (HMS) are stabilized in both the Re-free and Re-substituted HMSs, and the chemical formulae become Mn15Si26 and Ma(19)Si(33), respectively. The Re atoms are successfully substituted for Mn in the (Mn,Re)(19)Si-33 HMS. The number density of the sublattice dislocation in the Re-substituted HMS is 1.6 times higher than that in the Re-free HMS, that causes a decrease in lattice thermal conductivity. Due to the impurity effect of the Re substitution, the electrical conductivity is supposed to be enhanced, resulting in the highest dimensionless figure of merit (ZT) among the investigated HMSs. (C) 2018 Elsevier B.V. All rights reserved.