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 in situ 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 a 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.

Significant improvement in Mn2O3 transition metal oxide electrical conductivity via high pressure

“…Hence, the electronic transition near 5 GPa originates from a reversible structural phase transition. Similar results have been reported on other materials20. The microstructural change after high-pressure treatment should be responsible for the enhanced conductivity behavior.…”

“…Therefore, improving the intrinsic electrical conductivity of transition metal oxides for high-performance energy storage is imperative. Recent works have shown pressured-induced electron transport enhancement of Nb-doped TiO 2 nanoparticles and single-crystal Ta 2 O 5 nanowires1920 and there are further reports of pressure-induced superconductivities2122. Therefore, pressure may be a powerful tool to modify the electrical conductivity of transition metal oxides.…”

Measurement and Modeling of Short and Medium Range Order in Amorphous Ta2O5 Thin Films

“…Figure 2c shows a simulation of the PDF based on the PSU proposed above, calculated using the PDFgui software package35, indicating again that the PSU adequately represents the short-range structure of amorphous tantala. The assignment of pair correlations below 4 Å are broadly consistent with recent studies on amorphous tantala as well as tantala-based glasses3637383940. Taken together, the kinked Ta-O-Ta backbone of the proposed PSU appears to be a common, but previously unrecognized, fundamental building-block.…”

Europium Doped TiO2−Ta2O5 Heterostructure for Photodegradation of Dyes

“…A slight shift in the E g Raman mode of 0.5Eu90Ti−Ta is due to the doping effect of europium. The Raman bands between 100 and 450 cm −1 are associated with the O−Ta−O bending vibrations in TaO 6 octahedra, while those between 450 and 900 cm −1 mainly related to the various Ta−O stretching vibrations of edge shared polyhedral distortion . The UV‐Visible absorbance spectrum of 0.5Eu−TiO 2 and 0.5Eu90Ti−Ta samples exhibit improved absorption in the visible region than the pure TiO 2 .…”