Time-Resolved X-Ray Powder Diffraction Study of Photoinduced Phase Transitions in Ti 3 O 5 Nanoparticles.

Nanoparticles of Ti3 O5 have been reported to show a permanent photoinduced phase transition at room temperature. This suggests that light-induced phase transformations of Ti3 O5 nanoparticles may be promising for technological applications. Here, we report a photoinduced semiconductor-to-metal phase transition from β-Ti3 O5 to λ-Ti3 O5 nanoparticles at room temperature observed directly by time-resolved X-ray powder diffraction in a pump-probe setup. The results show a partial structural change, limited by differences between pumped and probed volumes, which persists a few microseconds after excitation. The first step in the relaxation back to the ground state can be described by a single exponential decay with time constant within microsecond timescales. Analysis of the change in lattice constants enables us to estimate an average temperature increase across the phase transition, consistent with a thermally driven process.