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

Yi Ma,Yuxuan Song,Taihua Zhang,Xianwei Huang,Julong Yuan,Wei Hang

doi:10.3390/ma12172799

Abstract

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.

Highlights

As a relatively new synthetic piezoelectric material lithium tantalate (LiTaO3 ) single crystal has been extensively adopted in the commercial laser and communication fields due to their prominent optical and electrical properties [1]
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

Summary

Introduction

As a relatively new synthetic piezoelectric material lithium tantalate (LiTaO3 ) single crystal has been extensively adopted in the commercial laser and communication fields due to their prominent optical and electrical properties [1]. The most well-known application of LiTaO3 single crystal is in the field of surface acoustic wave (SAW) devices [2], for its low acoustic loss. The thickness and surface quality are two important factors for LiTaO3 single crystal, which significantly influence the efficiency and functionality of LiTaO3 -based devices. For an ultrathin LiTaO3 single crystal wafer, the risk of catastrophic brittle fracture is increased during machining processes and application service in comparison to its bulk counterpart. Tiny defects such as scratches and damage on the surface layer could result in fracture of the thinned LiTaO3 single crystal. The crystal orientation plays an important role in mechanical properties such elastic modulus, hardness, and fracture morphology in LiTaO3 single crystal [5,6,7]

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Conclusion