Time-resolved Raman spectroscopy for monitoring the structural evolution of materials during rapid compression

Abstract

Rapid compression experiments performed using a dynamic diamond anvil cell (dDAC) offer the opportunity to study compression rate-dependent phenomena, which provide critical knowledge of the phase transition kinetics of materials. However, direct probing of the structure evolution of materials is scarce and so far limited to the synchrotron based x-ray diffraction technique. Here, we present a time-resolved Raman spectroscopy technique to monitor the structural evolutions in a subsecond time resolution. Instead of applying a shutter-based synchronization scheme in previous work, we directly coupled and synchronized the spectrometers with the dDAC, providing sequential Raman data over a broad pressure range. The capability and versatility of this technique are verified by in situ observation of the phase transition processes of three rapid compressed samples. Not only the phase transition pressures but also the transition pathways are reproduced with good accuracy. This approach has the potential to serve as an important complement to x-ray diffraction applied to study the kinetics of phase transitions occurring on time scales of seconds and above.

A high-pressure phase of Na2CuF4 with eight-coordinated Cu2+ – a low-pressure analogue of Mg2SiO4

“…41–44 Phase transitions are most often signalled in the Raman spectrum by the appearance or disappearance of vibrational bands and/or changes in the slopes of their pressure dependence. 45 Importantly, assignment of the structure of the high-pressure phases can be performed by comparing the experimental spectrum with that derived from DFT modelling. 46,47…”