A Crystallographic Study on the Growth of Partially Faceted MnSn2 Phase during Solidification Process

Abstract

The growth of MnSn2 phase during the solidification process of Sn-Mn alloy was crystallographically investigated. The results show that the non-faced spherical caps of the MnSn2 crystals follow the continuous growth mechanism to grow rapidly along the <001> direction, while the side surfaces the two-dimensional nucleation mechanism to form the low index {100} and {110} facets. An interface structure analysis indicates that the atom planes within the {100} interplanar spacing period (IPSP) has a lower average reticular density than those within the {011} IPSP. This leads to the faster growth rates and thus the shortening and disappearance of the {100} side facets. As a consequence, the partially faceted (i.e., non-faceted spherical caps and faceted side surfaces) MnSn2 crystals follow an octagonal-base/spherical-cap geometric model (few crystals possess square bases) in three dimensions.

Alignments and Orientations of MnSn₂ Phase during the Solidification Process of Sn–Mn Alloy under a High Magnetic Field

“…In our previous work, we have shown that a typical MnSn 2 crystal follows an octagonal-base/spherical-cap geometric model (few possess square bases) in three dimensions. 19) And such anisotropic shape is kinetically related to its anisotropic crystal structure. Therefore, the HMF-induced alteration to the alignments of the MnSn 2 crystals in this work should be accompanied by modification of the crystallographic orientations.…”

“…When a HMF is employed, however, the MnSn 2 crystals will be subjected to an external magnetic torque due to the magnetic anisotropy. As analysed elsewhere in detail, 16,19) the magnetization energy U i (per unit volume) of an anisotropic crystal induced by a magnetic field can be expressed as…”

“…5(a) and (b) schematically show the 3D alignments of the primary MnSn 2 crystals without and with the 12 T HMF, respectively (see Ref. 19) for more information about the 3D morphology of a single MnSn2 crystal). From these two schemes, it can be understood that the two-dimensional shapes of the primary MnSn 2 crystals strictly depend on their crystallographic orientations with respect to the observation sections.…”