Dislocation-based crack initiation and propagation in single-crystal SrTiO3

Fang, Xufei; Ding, Kuan; Minnert, Christian; Nakamura, Atsutomo; Durst, Karsten

doi:10.1007/s10853-020-05587-2

Cited by 20 publications

(32 citation statements)

References 63 publications

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“…They observed crack formation from the interaction between the slip bands. Crack arising from slip bands was also observed in MgO single crystals in bulk compression tests by Stokes et al 87 and Argon et al 88 Very recently, Fang et al 63 studied the dislocation pileups induced by spherical indenter tip on (001) plane of single‐crystal SrTiO 3 . By choosing a proper spherical indenter tip radius ( R = 2 μm), they captured the crack initiation due to dislocation pileups using the etch pit method.…”

Section: Discussionmentioning

confidence: 78%

“…Therefore the critical crack length,

c_{0}

, can be estimated by the following equation:

c_{0} = {()(, \frac{K_{Ic}}{\sqrt{π}})}^{2} {()(, \frac{2 π {()(, 3 P R)}^{2 / 3}}{false(1 ‐ 2 v false) {(4 E_{r})}^{2 / 3} P})}^{2} = {()(, \frac{K_{Ic}}{\sqrt{π}})}^{2} {()(, \frac{2 π}{(1 ‐ 2 v) P})}^{2} {()(, \frac{3 P R}{4 E_{r}})}^{4 / 3} = 4 π {()(, \frac{K_{Ic}}{(1 ‐ 2 v) P})}^{2} a_{0}^{4}

where

a_{0} = {()(, \frac{3 P R}{4 E_{normalr}})}^{1 / 3}

is the contact radius. Equation () is equivalent to the Griffith energy approach 63 if

K_{Ic}^{2} = 2 E γ_{normals}

is taken for brittle solids. Note this holds true for linear elastic fracture in the absence of crack tip blunting, as in the case of most ceramics where no crack tip dislocation emission is observed at room temperature.…”

Section: Discussionmentioning

confidence: 99%

“…It is worthy of note that in crystalline materials such as oxides and semiconductors, the shear fault surfaces correspond to the slip planes. Therefore, a more detailed examination of the dislocation interactions within these slip planes is of great interest to understand the dislocation‐based crack formation and propagation 63 …”

Section: Discussionmentioning

confidence: 99%

“…Yet it is no easy task to determine the R c as the boundary conditions would have to involve and must be dependent on the target material (different deformation mechanisms, slip systems, different lattice friction stress, Burgers vector), sample surface condition (distribution and density of pre‐existing defects due to sample preparation 90 ), chemical environment (humidity, surface chemistry, reducing atmosphere, etc. ), loading rate, tip material (harder diamond tip or softer sapphire tips), and machine dynamics 63,91 in load‐controlled machines. In addition, the complexity lies in the concurrent plastic deformation and crack formation during the pop‐in event for large indenter tip, making it challenging to discern the sequence of these two deformation processes at the on‐set of pop‐in.…”

Section: Discussionmentioning

confidence: 99%

“…To carefully separate them during dynamic deformation is a challenge where it is particularly difficult to induce dislocations without crack formation. A critical tip radius, R c , below which the pop‐in event correlates only to dislocations without crack formation, 63 is of great interest but yet is ambiguously defined.…”

Section: Introductionmentioning

confidence: 99%

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Nanoindentation pop‐in in oxides at room temperature: Dislocation activation or crack formation?

et al. 2021

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Most oxide ceramics are known to be brittle macroscopically at room temperature with little or no dislocation‐based plasticity prior to crack propagation. Here, we demonstrate the size‐dependent brittle to ductile transition in SrTiO3 at room temperature using nanoindentation pop‐in events visible as a sudden increase in displacement at nominally constant load. We identify that the indentation pop‐in event in SrTiO3 at room temperature, below a critical indenter tip radius, is dominated by dislocation‐mediated plasticity. When the tip radius increases to a critical size, concurrent dislocation activation and crack formation, with the latter being the dominating process, occur during the pop‐in event. Beyond the experimental examination and theoretical justification presented on SrTiO3 as a model system, further validation on α‐Al2O3, BaTiO3, and TiO2 are briefly presented and discussed. A new indentation size effect, mainly for brittle ceramics, is suggested by the competition between the dislocation‐based plasticity and crack formation at small scale. Our finding complements the deformation mechanism in the nano‐/microscale deformation regime involving plasticity and cracking in ceramics at room temperature to pave the road for dislocation‐based mechanics and functionalities study in these materials.

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Section: Discussionmentioning

confidence: 78%

“…Therefore the critical crack length,

c_{0}

, can be estimated by the following equation:

c_{0} = {()(, \frac{K_{Ic}}{\sqrt{π}})}^{2} {()(, \frac{2 π {()(, 3 P R)}^{2 / 3}}{false(1 ‐ 2 v false) {(4 E_{r})}^{2 / 3} P})}^{2} = {()(, \frac{K_{Ic}}{\sqrt{π}})}^{2} {()(, \frac{2 π}{(1 ‐ 2 v) P})}^{2} {()(, \frac{3 P R}{4 E_{r}})}^{4 / 3} = 4 π {()(, \frac{K_{Ic}}{(1 ‐ 2 v) P})}^{2} a_{0}^{4}

where

a_{0} = {()(, \frac{3 P R}{4 E_{normalr}})}^{1 / 3}

is the contact radius. Equation () is equivalent to the Griffith energy approach 63 if

K_{Ic}^{2} = 2 E γ_{normals}

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Nanoindentation pop‐in in oxides at room temperature: Dislocation activation or crack formation?

et al. 2021

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Understanding Nanoscale Plasticity by Quantitative In Situ Conductive Nanoindentation

2021

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Electronic materials such as semiconductors, piezo‐ and ferroelectrics, and metal oxides are primary constituents in sensing, actuation, nanoelectronics, memory, and energy systems. Although significant progress is evident in understanding the mechanical and electrical properties independently using conventional techniques, simultaneous and quantitative electromechanical characterization at the nanoscale using in situ techniques is scarce. It is essential because coupling/linking electrical signal to the nanoscale plasticity provides vital information regarding the real‐time electromechanical behavior of materials, which is crucial for developing miniaturized smarter technologies. With the advent of conductive nanoindentation, researchers have been able to get valuable insights into the nanoscale plasticity (otherwise not possible by conventional means) in a wide variety of bulk and small‐volume materials, quantify the electromechanical properties, understand the dielectric breakdown phenomenon and the nature of electrical contacts in thin films, etc., by continuously monitoring the real‐time electrical signal changes during any point on the indentation load–hold–unload cycle. This comprehensive Review covers probing the electromechanical behavior of materials using in situ conductive nanoindentation, data analysis methods, the validity of the models and limitations, and electronic conduction mechanisms at the nanocontacts, quantification of resistive components, applications, progress, and existing issues, and provides a futuristic outlook.

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Deformation Behavior and Fracture Strength of Single‐Crystal 4H‐SiC Determined by Microcantilever Bending Tests

Yahagi,

Ohji,

Yamaguchi

et al. 2024

Adv Eng Mater

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In this study, the deformation behaviors and mechanical properties of 4H‐SiC single crystals are investigated using microcantilever beam specimens with two different sizes, A and B (A < B). Tensile stress is applied along <20> direction. Plastic deformation, or nonlinearity, is observed in the stress–strain curves, and yield stress, or proportional limit, coincides between the two specimens at ≈25 ± 2 GPa. Scanning transmission electron microscopy and transmission electron microscopy studies show that the plastic deformation is due to dislocation activities; multiple‐dislocation pileup areas are observed in both the specimens. Assuming {100}/<110> prismatic slip which most plausibly occurs in the <20> stress application, the critical resolved shar stress is estimated to be 10.9 GPa, which agrees well with the previous studies. Measured fracture strength is 41.9 ± 2.8 and 33.5 ± 2.4 GPa for the A and B, respectively. Dislocation–fracture relationship is discussed on the basis of dislocation‐based fracture mechanics, etc. It is suggested that cracks form within the multiple‐dislocation pileup area, by interaction with dislocation pileups, and act as fracture origins. A's strength is close to an ideal tensile strength of 4H‐SiC in the <110> direction, 47–55 GPa.

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Dislocation-based crack initiation and propagation in single-crystal SrTiO3

Cited by 20 publications

References 63 publications

Nanoindentation pop‐in in oxides at room temperature: Dislocation activation or crack formation?

Nanoindentation pop‐in in oxides at room temperature: Dislocation activation or crack formation?

Understanding Nanoscale Plasticity by Quantitative In Situ Conductive Nanoindentation

Deformation Behavior and Fracture Strength of Single‐Crystal 4H‐SiC Determined by Microcantilever Bending Tests

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