Abstract:
The paper presents the results of an investigation into the synthesis of manganese silicides MnSi and MnSi$_{1.73}$, using aluminothermic reduction of metal oxides. Thermoelectric and magnetic properties of the obtained compounds have been studied. X-ray phase analysis showed that the alloy synthesized from the reaction mixture (MnO$_2$ + Si + Al) is single-phase with monosilicide silicon detected in its composition. However, the alloy synthesized from the reaction mixture (MnO$_2$ + SiO$_2$ + Al) is not single-phase as it contains phases such as MnSi$_{1.73}$, Mn$_2$Al$_5$Si$_5$, and a small amount of unreacted silicon. Microstructure of the alloys consists of homogeneous matrix with uniformly distributed pores. Thermoelectric measurements revealed that the sample prepared from the mixture (MnO$_2$ + Si + Al) exhibits hole conductivity, Seebeck coefficient equal to 30 muV/K at temperature 400 K, and electrical resistivity equal to 290 $\mu\Omega$$\Omega$ cm at temperature 1050 K. It was also shown that the alloys exhibit distinct ferromagnetic behavior, with saturation magnetization for MnSi (a) corresponding to Bohr magneton per Mn atom $\sim$0.5.
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