Abstract
Solid-solid phase transitions are processes ripe for the discovery of correlated atomic motion in crystals. Here, we monitor an order-disorder transition in real-time in nanoparticles of the super-ionic solid, Cu2−xSe. The use of in-situ high-resolution transmission electron microscopy allows the spatiotemporal evolution of the phase transition within a single nanoparticle to be monitored at the atomic level. The high spatial resolution reveals that cation disorder is nucleated at low co-ordination, high energy sites of the nanoparticle where cationic vacancy layers intersect with surface facets. Time-dependent evolution of the reciprocal lattice of individual nanoparticles shows that the initiation of cation disorder is accompanied by a ~3% compression of the anionic lattice, establishing a correlation between these two structural features of the lattice. The spatiotemporal insights gained here advance understanding of order-disorder transitions, ionic structure and transport, and the role of nanoparticle surfaces in phase transitions.
Highlights
Solid-solid phase transitions are processes ripe for the discovery of correlated atomic motion in crystals
We identify the precise atomic site where cation disordering is initiated and uncover correlated structural motions involved in the process
We filmed using in-situ high-resolution transmission electron microscopy (HRTEM) individual Cu2−xSe nanoparticles as they underwent a transition from the vacancy ordered (VO) phase to the SI phase (Fig. 1, Supplementary Movies 1 and 2)
Summary
Solid-solid phase transitions are processes ripe for the discovery of correlated atomic motion in crystals. We filmed using in-situ HRTEM individual Cu2−xSe nanoparticles as they underwent a transition from the VO phase to the SI phase (Fig. 1, Supplementary Movies 1 and 2). The temperature-dependent phase transition in an HNP was induced by the electron beam, which heats up the HNP3,30.
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