Crystal structure and thermoelectric properties of partially-substituted melt-grown higher manganese silicides

Crystal structure and thermoelectric properties of several partially-substituted higher manganese silicides (HMSs) samples have been reviewed. HMSs possess a unique incommensurate crystal structure consisting of two subsystems of [Mn] and [Si] and the structure formula is thus represented as MnSi gamma. The c-axis length ratio, gamma, changes with temperature to yield the MnSi (monosilicide) striations, which deteriorate mechanical strength and electrical conductivity. A small amount of V-substitution effectively dissipates such striations and enhances hole carrier concentration. Thus prepared V-substituted samples exhibit the highest power factor and remarkably lower thermal conductivity. The nanostructure of such samples consists of regular and highly disordered nano-domains of Si atoms, which would further reduce the thermal conductivity to enhance thermoelectric figure-of-merit. (c) 2020 The Japan Society of Applied Physics