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Approaching the Minimum Thermal Conductivity in Rhenium‐Substituted Higher Manganese Silicides |
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| Authors: | Xi Chen Steven N Girard Fei Meng Edgar Lara‐Curzio Song Jin John B Goodenough Jianshi Zhou Li Shi |
| Institution: | 1. Materials Science and Engineering Program, Texas Materials Institute, The University of Texas at Austin, Austin, TX, USA;2. Department of Chemistry, University of Wisconsin ? Madison, Madison, WI, USA;3. Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA |
| Abstract: | Higher manganese silicides (HMS) made of earth‐abundant and non‐toxic elements are regarded as promising p‐type thermoelectric materials because their complex crystal structure results in low lattice thermal conductivity. It is shown here that the already low thermal conductivity of HMS can be reduced further to approach the minimum thermal conductivity via partial substitution of Mn with heavier rhenium (Re) to increase point defect scattering. The solubility limit of Re in the obtained RexMn1‐xSi1.8 is determined to be about x = 0.18. Elemental inhomogeneity and the formation of ReSi1.75 inclusions with 50?200 nm size are found within the HMS matrix. It is found that the power factor does not change markedly at low Re content of x ≤ 0.04 before it drops considerably at higher Re contents. Compared to pure HMS, the reduced lattice thermal conductivity in RexMn1‐xSi1.8 results in a 25% increase of the peak figure of merit ZT to reach 0.57 ± 0.08 at 800 K for x = 0.04. The suppressed thermal conductivity in the pure RexMn1‐xSi1.8 can enable further investigations of the ZT limit of this system by exploring different impurity doping strategies to optimize the carrier concentration and power factor. |
| Keywords: | alloys thermoelectric materials thermal conductivity nanostructures silicides |