PRESSURE-INDUCED AMORPHIZATION AND REDUCTION OF T-NB2O5

Energy dispersive x-ray diffraction measurements show that the T phase of Nb2O5 becomes x-ray amorphous at a pressure of 19.2 GPa at 300 K. This pressure-induced amorphization is novel since the oxide is simultaneously reduced as it becomes amorphous. The amorphization occurs because the pressure-induced reduction T-Nb2O5 --> crystalline Nb12O29 is kinetically impeded. A consideration of the ambient pressure atomic mechanism of the oxidation of NbO(x) compounds (x < 2.5) suggests that the pressure-induced amorphous state is formed by oxygen defects in the T-Nb2O5 lattice.