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

• Published in: Journal of the American Chemical Society Vol. 135; no. 37; pp. 13947 - 13953
• Main Authors: Lü, Xujie, Hu, Qingyang, Yang, Wenge, Bai, Ligang, Sheng, Howard, Wang, Lin, Huang, Fuqiang, Wen, Jianguo, Miller, Dean J, Zhao, Yusheng
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 18.09.2013
• Subjects: electrical conductivity; geometry; monitoring; nanowires; phase transition; Raman spectroscopy; transmission electron microscopy; X-ray diffraction
• DOI: 10.1021/ja407108u
• ISSN: 0002-7863; 1520-5126

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.