Unveiling the Microscopic Origins of Phase Transformations: An in Situ TEM Perspective †

Nanostructuring inorganic solids has been effective as a tool to control the identity of the thermodynamically stable phase under ambient conditions for many systems. In addition, size effects can alter not only the temperature but also the other characteristics of a transformation - such as order, mechanism, and kinetics - which may further be responsible for the transient existence of intermediates, both thermodynamic and metastable, not accessed in the bulk. Since understanding the mechanism of a phase transformation requires local, even atomistic, information, and a similar understanding of the kinetics requires this information to be collected in real-time, in situ microscopy has proved invaluable in identifying key features of transformations on the nanoscale and promises to play a key role in the future design and implementation of such systems. Here, we discuss the use of in situ heating and biasing in the transmission electron microscope to investigate phase transformations in inorganic, single-phase, solid-state, nanostructured systems.