Orientation-Independent Yield Stress and Activation Volume of Dislocation Nucleation in LiTaO3 Single Crystal by Nanoindentation

• Published in: Materials 2019-08, Vol.12 (17), p.2799
• Main Authors: Ma, Yi, Huang, Xianwei, Song, Yuxuan, Hang, Wei, Yuan, Julong, Zhang, Taihua
• Format: Article
• Language: English
• Subjects: Crystal defects; Crystal dislocations; Crystal structure; Load; Mechanical properties; Nanoindentation; Nucleation; Orientation effects; Plastic properties; Shear strength; Shear stress; Single crystals; Statistical analysis; Stress concentration; Yield strength; Yield stress
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma12172799

Relying on nanoindentation technology, we investigated the elastic-to-plastic transition via first pop-in event and estimated the corresponding shear stress for incipient plasticity, i.e., yielding in the three typical orientations, i.e., X-112°, Y-36°, and Y-42° planes. The occurrence of incipient plasticity exhibited a stochastic distribution in a wide range for the three orientations. Accordingly, the obtained values of yield stress were uniform and scattered in the range from about 4 to 7 GPa for LiTaO3 single crystal. The orientation effect on yield stress at the nano-scale was revealed to be insignificant in LiTaO3 single crystal. The yield stresses were 5.44 ± 0.41, 5.74 ± 0.59, and 5.34 ± 0.525 GPa for the X-112°, Y-36°, and Y-42° planes, respectively. The activation volumes of dislocation nucleation were computed based on the cumulative distribution of yield stress, which were 12 Å3, 8 Å3, and 9 Å3 for the X-112°, Y-36°, and Y-42° planes. The results indicated that point-like defects could be the source of plastic initiation on the surface of LiTaO3 single crystal.