Microstructure and structural modulation of lutetium dihydride LuH2 as seen via transmission electron microscopy

TL;DR

This study uses transmission electron microscopy to analyze the microstructure and structural modulations of lutetium dihydride, revealing superstructure modulations, antiphase boundaries, and temperature stability of the structure.

Contribution

The paper provides detailed TEM analysis of LuH2, highlighting microstructural phenomena and effects of nitrogen doping under high pressure, which were previously uncharacterized.

Findings

Both AP-LuH2 and HP-LuH2 show superstructure modulation with wave vector q* = 1/4 (2-20).

Nitrogen-doped HP-LuH2 exhibits high-density antiphase boundaries and domain walls.

No significant structural phase transition occurs between 94 K and 673 K.

Abstract

Structural investigations conducted using transmission electron microscopy (TEM) on LuH2 synthesized under atmospheric pressure (AP-LuH2) and nitrogen-doped LuH2 synthesized under high pressure (HP-LuH2) have revealed numerous microstructural phenomena. Both materials show a clear superstructure modulation with wave vector, q^* = 1/4 (2-20), and this modulation can be well interpreted by the displacements of Lu atoms. Further investigations on the nitrogen-doped HP-LuH2 materials reveal the appearance of high-density antiphase boundaries, in particular, domain walls of a few atomic layer thickness without structural modulation can be observed, suggesting possible interface properties could be detected in this system. In-situ TEM observations of AP-LuH2 suggest that no evident structural phase transition occurs between 94 K and 673 K.