Fang, Xufei (2024)
Room-temperature Dislocations in Ceramics: Engineering, Mechanism, and Application.
Universitäts- und Landesbibliothek Darmstadt, 2024
doi: 10.26083/tuprints-00027351
Habilitation, Zweitveröffentlichung, Verlagsversion

Kurzbeschreibung (Abstract)

Advanced functional ceramics play an indispensable role in our modern society and they are typically engineered by point defects or interfaces. The potential of dislocations (one-dimensional atomic distortions or line defects) in functional ceramics has been much underappreciated. Most recently, exciting proofs-of-concept have been demonstrated for dislocation-tuned functionality (e.g., electrical conductivity, superconductivity, and ferroelectric properties) and mechanical properties (e.g., plasticity and fracture toughness), revealing a new horizon of dislocation technology in ceramics for a wide range of possibilities for next-generation applications from sensors, actuators, to energy converters. However, it is widely known that ceramics are hard (difficult to deform) and brittle (easy to fracture), posing a great challenge to tailor dislocations in ceramics, particularly at room temperature. This pressing bottleneck hinders the dislocation-tuned functionality and mechanical properties, hence the true realization of dislocation technology. To address this pressing bottleneck, this Habilitation demonstrates the mechanics-based dislocation engineering in ceramics by examining the three fundamental factors (dislocation nucleation, dislocation multiplication, and dislocation motion) to reveal the underlying deformation mechanisms, with a focus on room-temperature plasticity in ceramics. Successful experimental approaches to tune dislocation density and plastic zone size on single-crystal strontium titanate (SrTiO3) are showcased, with an extension to other materials presented later. The dislocation-based competition between plastic deformation (dislocation nucleation, multiplication, and motion) and crack formation (crack initiation and crack propagation) is discussed. The aspects of coupling external fields to manipulate dislocations are briefly highlighted, which may hold the key to modulating the charged dislocation cores in ceramics and opening new routes for mechanical tailoring of dislocations at room temperature in the near future. Approaching the end, promising proofs-of-concept for dislocation-tuned functional and mechanical properties are presented. Finally, some open questions and challenges for dislocations in ceramics are discussed. This Habilitation aims to lay a foundation to fulfill the key prerequisite of dislocation-tuned functional and mechanical properties by addressing mechanics-based dislocation engineering in ceramics (with a focus on room-temperature deformation). This work aims to provide a new platform for engineering functional ceramics using dislocations.

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