Synthesis of MnSi1.7 nanosheet bundles from CaSi2 crystal powders using MnCl2 in molten salt

Abstract

MnSi1.7 nanosheet bundles with an improved homogeneous composition were synthesized by annealing from CaSi2 crystal powders with MnCl2 in molten salt. The MnSi and Si phases were formed at the initial stage of the synthesis with an inhomogeneous Mn distribution within the nanosheet bundles. Subsequently, the phases were transformed into MnSi1.7 with an improved homogeneous Mn distribution within them for 10 h annealing in the molten salt. The formation of multiple Mn-silicide phases and remarkable improvement in the structural homogeneity of the MnSi1.7 nanosheet bundles were discussed in terms of the reactions of Mn or Si with chloride compounds, decomposition of chlorides at elevated temperatures, phase selection of multiple silicide phases, shrinkage of the volume from Si to MnSi1.7, and dominant diffusion species. Multiple growth variants of the MnSi1.7 domains were stacked in the nanosheets. For comparison, the growth in a deliquescent environment realized by NH4Cl addition was examined. (c) 2023 The Japan Society of Applied Physics