Three-Dimensional Imaging of a Long-Period Stacking Ordered Phase in Mg₉₇Zn₁Gd₂ Using High-Voltage Electron Microscopy

Abstract

Spatial configurations and lateral morphology of the 14H long-period stacking ordered (LPSO) phase have been studied by single tilt-axis electron tomography using high-voltage scanning transmission electron microscopy (STEM) operated at 1 MV. A “Quonset hut-like” lateral shape of the LPSO was found in a tomogram of a specimen as thick as 1.7 μm. The reconstructed volume reveals spatial distribution of residual particulate precipitates of (Mg, Zn)₃Gd phase 20–30 nm in diameters. The precipitates act as a source of solute elements for the formation and growth processes of 14H LPSO. 1 MV-STEM realizes enough resolution for imaging the morphology of LPSO as well as high electron transmittance (~4.1 μm) without any obvious electron irradiation damages on microstructures.