High Pressure Science and Engineering Center, University of Nevada , Las Vegas, Nevada 89154, United States.
J Am Chem Soc. 2013 Sep 18;135(37):13947-53. doi: 10.1021/ja407108u. Epub 2013 Sep 6.
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.
在 19GPa 下观察到 Ta2O5 单晶纳米线的压力诱导非晶化（PIA），所得非晶 Ta2O5 纳米线的电导率显著提高。通过原位同步辐射 X 射线衍射、配分函数、拉曼光谱和透射电子显微镜监测结构演变，揭示了相变过程。第一性原理计算揭示了在特定键合处压缩过程中声子模式软化，电子定域函数分析也表明在相同位置键合强度减弱。基于实验和理论结果，系统地提出并证明了一种动力学 PIA 机制，即非晶化是由单元中沿 a 轴的特定弱键位置的多面体（TaO6 八面体或 TaO7 双锥）之间的连通性破坏引发的。压力诱导的 Ta2O5 非晶保留了一维形态，与传统非晶形式相比，电导率提高了一个数量级。这种具有独特性能的压力诱导非晶纳米材料超越了晶态或传统非晶态的性能，有望在未来的许多应用中得到广泛应用。
