Evolution of phase transitions in yttria (Y₂O₃) ceramics induced by nanosecond shock loading

Structural phase transitions of yttria (Y₂O₃) ceramic driven by shock compression were investigated by a pump-probe method using in situ time-resolved synchrotron X-ray diffraction. Shock compression on the yttria sample was performed by pump-laser irradiation on a target surface. The onset of the structural phase transition from the cubic (C-type) to the monoclinic (B-type) phase was observed at several nanoseconds after the start of the pump-laser irradiation. Raman spectra of the shock-recovered sample confirmed the occurrence of the phase transition and its irreversible nature. Although the phase transition is accompanied by a large volume change and large-scale rearrangement of atoms, the initiation of the phase transition was realized during the shock-pressure loading, which lasted several nanoseconds.