Structural Anisotropy-Driven Atomic Mechanisms of Phase Transformations in the Pt-Sn System

Using in situ atomic-resolution scanningtransmissionelectron microscopy, atomic movements and rearrangements associatedwith diffusive solid to solid phase transformations in the Pt-Snsystem are captured to reveal details of the underlying atomisticmechanisms that drive these transformations. In the PtSn4 to PtSn2 phase transformation, a periodic superlatticesubstructure and a unique intermediate structure precede the nucleationand growth of the PtSn2 phase. At the atomic level, allstages of the transformation are templated by the anisotropic crystalstructure of the parent PtSn4 phase. In the case of thePtSn(2) to Pt2Sn3 transformation, theanisotropy in the structure of product Pt2Sn3 dictates the path of transformation. Analysis of atomic configurationsat the transformation front elucidates the diffusion pathways andlattice distortions required for these phase transformations. Comparisonof multiple Pt-Sn phase transformations reveals the structuralparameters governing solid to solid phase transformations in thistechnologically interesting intermetallic system.

Automated summary

Using atomic-resolution scanning transmission electron microscopy, this study captures atomic movements and rearrangements in the Pt-Sn system during solid-solid phase transformations, providing details of the underlying mechanisms. The PtSn4 to PtSn2 transformation is preceded by a periodic superlattice substructure and an intermediate structure templated by the anisotropic crystal structure of the parent phase. The PtSn(2) to Pt2Sn3 transformation is dictated by the anisotropy of the product Pt2Sn3 structure. Analysis of atomic configurations at the transformation front reveals the diffusion pathways and lattice distortions involved. Comparison of multiple transformations in the Pt-Sn system elucidates the structural parameters governing solid-solid phase transformations in this intermetallic system.