Pressure-Induced Amorphization in Single-Crystal Ta₂O₅ Nanowires: A Kinetic Mechanism and Improved Electrical Conductivity

Abstract

Pressure-induced amorphization (PIA) in single-crystal Ta₂O₅ nanowires is observed at 19 GPa, and the obtained amorphous Ta₂O₅ nanowires show significant improvement in electrical conductivity. The phase transition process is unveiled by monitoring structural evolution with <i>in situ</i> synchrotron X-ray diffraction, pair distribution function, Raman spectroscopy, and transmission electron microscopy. The first principles calculations reveal the phonon modes softening during compression at particular bonds, and the analysis on the electron localization function also shows bond strength weakening at the same positions. On the basis of the experimental and theoretical results, a kinetic PIA mechanism is proposed and demonstrated systematically that amorphization is initiated by the disruption of connectivity between polyhedra (TaO₆ octahedra or TaO₇ bipyramids) at the particular weak-bonding positions along the <i>a</i> axis in the unit cell. The one-dimensional morphology is well-preserved for the pressure-induced amorphous Ta₂O₅, and the electrical conductivity is improved by an order of magnitude compared to traditional amorphous forms. Such pressure-induced amorphous nanomaterials with unique properties surpassing those in either crystalline or conventional amorphous phases hold great promise for numerous applications in the future