Chimney–Ladder Pseudo-Binary p-Type (Mn, Cr)Siγ Compounds for Mid-Temperature Silicide-Based Thermoelectrics

Abstract

Higher manganese silicides (MnSi_γ), a class of Nowotny chimney-ladder (NCL) intermetallic compounds with complex incommensurate crystal structures, are promising candidates for realizing high-performance all-silicide thermoelectric modules. Herein, we explore quenching-induced structural disorder in melt-spun pseudo-binary Mn_1–xCr_xSi_1.74 (0 ≤ x ≤ 0.20) compositions for hole concentration optimization and stabilization of high-temperature electronic transport. Incorporated Cr atoms into the [Mn] subsystem concomitantly modify the twisting pitch of the Si ladder while sustaining the incommensurate modulation. The Cr substitution increases the carrier concentration, which enhances the electrical conductivity significantly, leading to an improved power factor at high temperatures, while strain field effects from substitutional disorder lowered the lattice thermal conductivity (κ_L) ≈ 1.5 W m^–1 K^–1 synergistically, to improve the thermoelectric figure of merit (zT) ≈ 0.6 (±0.1) at 823 K for the bulk Mn_0.92Cr_0.08Si_1.74 polycrystals. This work highlights the prospects of pseudo-binary transition-metal silicides for advancing p-type silicide thermoelectrics toward practical module integration in mid-temperature power generation applications.