Pressure-induced structural transition in WO3 nanowires.

Raman spectroscopic analysis is performed on WO(3) nanowires at room temperature at pressures from ambient conditions to 45 GPa. Linear dependence of the first-order Raman signal on various high-pressure (HP) sections is observed. Upon increasing the applied pressure, the WO(3) nanowires undergo four phase transitions at pressures around 1.7, 4.6, 21.5, and 26.2 GPa, which are all less than that reported for bulk WO(3). When the pressure is up to 42.5 GPa, a new high-pressure phase (HP5) appears. This phase has never been reported and is not reversible while unloading the pressure.