Abstract:Dislocations have been identified to modify both the functional and mechanical properties of some ceramic materials. Succinct control of dislocation-based plasticity in ceramics will also demand knowledge about dislocation interaction with point defects. Here, we propose an experimental approach to modulate the dislocation-based plasticity in single-crystal SrTiO 3 based on the concept of defect chemistry engineering, for example, by increasing the oxygen vacancy concentration via reduction treatment. With nan… Show more
“…5 ). In a word, the oxygen reduction is adverse to the dislocation motion, which also agrees with the recently published experimental works 47 , 48 . Fig.…”
Section: Resultssupporting
confidence: 92%
“…In our calculation, the average misfit energy decreases after introducing oxygen vacancies, indicating that oxygen vacancies contribute to the nucleation of dislocation in SrTiO 3 . The results agree well with the recently published experimental works on SrTiO 3 47 , 48 , in which the SrTiO 3 with higher vacancy concentration favors the dislocation nucleation.…”
An in-depth understanding of the dislocations motion process in non-metallic materials becomes increasingly important, stimulated by the recent emergence of ceramics and semiconductors with unexpected room temperature dislocation-mediated plasticity. In this work, local misfit energy is put forward to accurately derive the Peierls stress and model the dislocation process in SrTiO3 ceramics instead of the generalized stacking fault (GSF) approach, which considers the in-plane freedom degrees of the atoms near the shear plane and describes the breaking and re-bonding processes of the complex chemical bonds. Particularly, we discover an abnormal shear-dependence of local misfit energy, which originates from the re-bonding process of the Ti-O bonds and the reversal of lattice dipoles. In addition, this approach predicts that oxygen vacancies in the SrTiO3 can facilitate the nucleation and activation of dislocations with improvement of fracture toughness, owing to the reduction of average misfit energy and Peierls stress due to the disappearance of lattice dipole reversal. This work provides undiscovered insights into the dislocation process in non-metallic materials, which may bring implications to tune the plasticity and explore unknown ductile compositions.
“…5 ). In a word, the oxygen reduction is adverse to the dislocation motion, which also agrees with the recently published experimental works 47 , 48 . Fig.…”
Section: Resultssupporting
confidence: 92%
“…In our calculation, the average misfit energy decreases after introducing oxygen vacancies, indicating that oxygen vacancies contribute to the nucleation of dislocation in SrTiO 3 . The results agree well with the recently published experimental works on SrTiO 3 47 , 48 , in which the SrTiO 3 with higher vacancy concentration favors the dislocation nucleation.…”
An in-depth understanding of the dislocations motion process in non-metallic materials becomes increasingly important, stimulated by the recent emergence of ceramics and semiconductors with unexpected room temperature dislocation-mediated plasticity. In this work, local misfit energy is put forward to accurately derive the Peierls stress and model the dislocation process in SrTiO3 ceramics instead of the generalized stacking fault (GSF) approach, which considers the in-plane freedom degrees of the atoms near the shear plane and describes the breaking and re-bonding processes of the complex chemical bonds. Particularly, we discover an abnormal shear-dependence of local misfit energy, which originates from the re-bonding process of the Ti-O bonds and the reversal of lattice dipoles. In addition, this approach predicts that oxygen vacancies in the SrTiO3 can facilitate the nucleation and activation of dislocations with improvement of fracture toughness, owing to the reduction of average misfit energy and Peierls stress due to the disappearance of lattice dipole reversal. This work provides undiscovered insights into the dislocation process in non-metallic materials, which may bring implications to tune the plasticity and explore unknown ductile compositions.
“…In both cases, they argued that such effect is most likely due to impurities. The current authors have proposed that oxygen vacancies may segregate to dislocations and pin the dislocations at RT, hence, reducing the dislocation mobility as evidenced by the indentation creep tests on single‐crystal SrTiO 3 with higher oxygen vacancy concentrations 17,19 . In the current case at 1373 K, we first consider oxygen vacancies () as the most dominant fast diffusing species in SrTiO 3 19 .…”
Section: Discussionmentioning
confidence: 99%
“…Undoped single‐crystal SrTiO 3 plates with a dimension of about 2.5 mm × 2.5 mm × 1 mm are used (Alineason Materials Technology GmbH, Frankfurt am Main, Germany). The samples were polished on one side following the detailed procedure described in our previous work 17 to avoid surface mechanical deformation. Surfaces of (001) were chosen for mechanical deformation as they can be chemically etched.…”
Dislocation‐tuned functionality in ceramic oxides for potential versatile applications gains increasing attention. As the widespread chemical doping suffers from poor temperature stability, dislocations in well‐controlled mesoscopic structure may be an alternative to thermally stable intrinsic doping features. To this end, the dislocation density in plastic zones introduced by cyclic Brinell indentation is considered under thermal annealing conditions. The considerably enhanced dislocation density due to thermal treatment is found to impact both microhardness and fracture toughness, albeit only to a modest degree. The mechanistic understanding centers around enhanced mobility and multiplication of the pre‐engineered dislocations at elevated temperatures driven by the residual indentation stress, as well as the strengthened interaction of point defects and dislocations at high temperature.
“…These deviatoric stress levels can also be reached with additional hydrostatic stresses to prevent cracking 132,201 , which is relevant for geology [132][133][134] . Defects, however, can lower the required stress for dislocation nucleation substantially 78,202 . Indenting with an appropriate tip size allows testing the local plasticity and determine whether nucleation is necessary or not.…”
Section: Limitation By the Necessity Of Nucleationmentioning
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.
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