By Cameron Chai
A research team at the Lawrence Berkeley National Laboratory (Berkeley Lab) of the U.S. Department of Energy (DOE) has investigated structural variations in a copper sulfide nanocrystal during its transition from low to high-chalcocite solid-state phase using transmission electron aberration-corrected microscope (TEAM) 0.5.
HRTEM micrographs showing the low-chalcocite (left) and high-chalcocite atomic structures of a copper sulfide nanorod
The study helps in knowing the structural changes in solid materials at the interface between an electrolyte and an electrode, or the ion transportation that happens inside the electrodes during the discharging or charging process of batteries. The results of the study will help in the development of next-generation energy technologies.
Paul Alivisatos, who serves as director at Berkeley Lab and leads the research team, stated that the defects found in the nanorod crystal are the influential factors behind structural transformation dynamics. The results of the study recommend methods for helping or repressing these structural transformations in order to develop materials with unique and controlled phases, he added.
During temperature changes, nanoscale solid materials demonstrate two more phase transformations in its crystal structure. For instance, copper sulfide nanocrystal can be transitioned from an intricate hexagonal pattern called the low-chalcocite phase to a relatively simple hexagonal pattern called the high-chalcocite phase.
Alivisatos stated that the energetic barrier of nanoscale systems to their structural transition expands with their size. Phase transition theory explains that a solid crystal will vary between two equilibrium patterns close to the phase transformation point prior to attaining a stable structure. This transformation region widens in nanocrystals. To study this theory, the research team observed the expected fluctuations of copper sulfide nanorods under the TEAM 0.5 microscope’s electron beam.