Nanoscale to microscale reversal in room-temperature plasticity in SrTiO3 by tuning defect concentration

Fang, Xufei; Ding, Kuan; Janocha, Stephan; Minnert, Christian; Rheinheimer, Wolfgang; Frömling, Till; Durst, Karsten; Nakamura, Atsutomo; Rödel, Jürgen

doi:10.1016/j.scriptamat.2020.07.033

Cited by 32 publications

(62 citation statements)

References 47 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Therefore, in indentation tests with a small indenter tip radius (e.g. R = 90 nm 34 ), the maximums shear stress

τ_{max}

in Equation () required to nucleate dislocations in dislocation‐free ceramics would approach the theoretical shear strength, which is estimated with an upper bound as

G / 2 π

, 69 with G being the shear modulus. Consider the general case (isotropic) that

G = E / 2 (1 + v)

and

v \approx 0.3

, this gives an upper bound of theoretical shear strength as:

τ_{th} \approx \frac{G}{2 π} \approx \frac{E}{16}

…”

Section: Theoretical Considerationmentioning

confidence: 99%

“…The sample surfaces were polished by diamond abrasives first and then finished by vibrational polishing with colloidal silica to remove the surface mechanical deformation layer, where an extremely low dislocation density of ~10 10 m −2 is shown by the etch pit study (Figure ). The surface roughness is checked using atomic force microscopy (AFM, Vecco, Plainview, NY, USA) to ensure a small average surface roughness (e.g., <1 nm for SrTiO 3 34 ) before the indentation tests. Details on sample preparation of the other three oxides (Al 2 O 3 , BaTiO 3 , and TiO 2 ) for the purpose of validation are provided in the .…”

Section: Experimental Preparationmentioning

confidence: 99%

“…for bi‐crystals of high quality. Third, dislocations can be introduced into samples by mechanical deformation, for example, via bulk compression at room temperature 28‐32 or high temperature, 13,15,33 by near surface mechanical treatment using nanoindentation at a small scale, 34‐40 micro‐scratching/machining, 41 and so on. While the first two approaches mainly involve processing and fabrication, the third approach relies on the dislocation mechanics of the target ceramic materials under mechanical loading.…”

Section: Introductionmentioning

confidence: 99%

“…Page et al 42 were among the first to point out that deformation in ceramics at very low load (nano)indentation could be mainly dominated by dislocation‐mediated plastic deformation, as in the case of sapphire. Further examples are available from nanoindentation tests on MgO, 37,43,44 ZrO 2 , 39 ZnO, 45 and SrTiO 3 32,34,35,46 . In addition to the examples in conventional instrumented nanoindentation studies with post‐mortem surface characterization, the advanced in situ TEM indentation study has been employed to directly reveal the dislocation activation in oxides without inducing cracks.…”

Section: Introductionmentioning

confidence: 99%

“…Pop‐in in load‐controlled nanoindentation refers to the sudden jump of the displacement during a specific threshold load, signifying the elastic‐plastic transition. The nanoindentation pop‐in behavior has been extensively studied in recent years in metallic materials 51‐58 but has been barely investigated in ceramics materials until very recently 12,34,59,60 . In metallic materials (without thin oxide film formed on the surface 61 ) the pop‐in indicates dislocation activation.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

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

et al. 2021

Self Cite

View full text Add to dashboard Cite

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.

show abstract

“…Therefore, in indentation tests with a small indenter tip radius (e.g. R = 90 nm 34 ), the maximums shear stress

τ_{max}

in Equation () required to nucleate dislocations in dislocation‐free ceramics would approach the theoretical shear strength, which is estimated with an upper bound as

G / 2 π

, 69 with G being the shear modulus. Consider the general case (isotropic) that

G = E / 2 (1 + v)

and

v \approx 0.3

, this gives an upper bound of theoretical shear strength as:

τ_{th} \approx \frac{G}{2 π} \approx \frac{E}{16}

…”

Section: Theoretical Considerationmentioning

confidence: 99%

Section: Experimental Preparationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

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

et al. 2021

Self Cite

View full text Add to dashboard Cite

show abstract

Understanding Nanoscale Plasticity by Quantitative In Situ Conductive Nanoindentation

2021

View full text Add to dashboard Cite

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.

show abstract

60 years of dislocations in ceramics: A conceptual framework for dislocation mechanics in ceramics

Porz

2022

Int J Ceramic Engine & Sci

View full text Add to dashboard Cite

High‐tech ceramics are typically engineered by controlling point defects and interfaces while one‐dimensional dislocations have found much less attention so far. Nevertheless, their impact on almost any functional property and the sudden ease to fabricate them with novel synthesis methods, such as rapid densification, brings spotlight attention to dislocations as design dimension. Although the typical brittleness of ceramics insinuates the irrelevance of dislocations for mechanical behavior, abundant literature is spread over materials, decades, and disciplines, however, often unconnected. Here, a conceptual framework for dislocation mechanics in ceramics separated into five logical aspects, (1) fundamental mobility, (2) obstacles to motion, (3) limitation by necessity of nucleation, (4) motion complexity, and (5) avoidance of competing mechanisms, brings oversight into the complex behavior. In consequence, quicker identification of the limiting step allows to estimate the potential involved more precisely and to identify open research questions with greater ease. An introduction to dislocations and the functionality involved, a look back over the last six decades, and highlights of open question are dedicated to provide a framework and bridge the gap between the attached research fields.

show abstract

Nanoscale to microscale reversal in room-temperature plasticity in SrTiO3 by tuning defect concentration

Cited by 32 publications

References 47 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

60 years of dislocations in ceramics: A conceptual framework for dislocation mechanics in ceramics

Contact Info

Product

Resources

About