Periodic Reporting for period 1 - MECERDIS (Mechanics-tailored Functional Ceramics via Dislocations)
Reporting period: 2023-04-01 to 2025-09-30
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) in functional ceramics has been greatly underestimated until most recently. Exciting proofs-of-concept have been demonstrated for dislocation-tuned functionality such as electrical conductivity, superconductivity, and ferroelectric properties, revealing a new horizon of dislocation technology in ceramics for a wide range of 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), making it a great challenge to tailor dislocations in ceramics. This pressing bottleneck hinders the dislocation-tuned functionality and the true realization of dislocation technology. To break through this bottleneck, project MECERDIS (Mechanics-Tailored Functional Ceramics via Dislocations) employs mechanics-guided design coupled with external fields (thermal, light illumination, electric field) to manipulate the 3 most fundamental factors of dislocation mechanics: nucleation, multiplication, and motion. These external fields greatly impact the charged dislocation cores in ceramics and open new routes for mechanical tuning. With these novel approaches, MECERDIS aims to generate, control, and stabilize dislocations in large plastic volumes up to mm-size with high density up to 10^15/m^2 to allow large-scale preparation for functionality assessment. Another essential benefit is, dislocations are an effective tool to combat the brittleness of ceramics by improving the damage tolerance and fracture toughness. In short, MECERDIS will not only fulfil the key prerequisite of dislocation-tuned functionality but also secure the mechanical integrity and operational stability of future dislocation-based devices. With its success, MECERDIS will define a new paradigm of engineering functional ceramics using mechanics and dislocations.
Project MECERDIS has developed several novel methodologies for dislocation engineering in ceramics, with a particular focus on room-temperature deformation at meso/macroscale, contrasting the conventional picture that this is impossible for ceramics due to their being hard and brittle. For instance, in Project MECERDIS, we have proposed the original idea of “mechanically seeded dislocations” to overcome the dislocation nucleation (which requires extremely high shear stress and most ceramics would have already fractured before such a high shear stress can be achieved) to facilitate the dislocation motion and multiplication, hence promoting the dislocation plasticity even at room temperature in various ceramic materials. This constitutes a fundamental component for Project MECERDIS to build up this so-called "Deformation toolbox" to mechanically engineer dislocations at room temperature across the length scales (from nanoscale up to bulk, i.e. millimeter or larger samples), with a tunable dislocaiton density over 4-5 orders of magnitude from e.g. 10^10/m^2 to 10^15/m^2, in a fast and cost-effective manner, holding great potential for applications.
Based on the "Deformation toolbox", the "Materials toolbox" is being extended as well. So far, the most "well-known" plastically deformation ceramics at macroscale at room temperature have been known to be e.g. rock salts, MgO, SrTiO3, with just a very limited total number of them, ever since the first studies dating back to the 1920s. Project MECERDIS has been able to report KTaO3 as the 3rd perovskite oxide to exhibit room temperature bulk plasticity in 2024. This discovery has already generated a huge impact in the ceramic community, considering the 1st one being SrTiO3 was reported in 2001, and the 2nd one being KNbO3 reported in 2016. This breakthrough indeed opens many new doors for Project MECERDIS to extend the materials much more beyond just these 3 materials, using the “alloying” concept borrowed from the metal community, and the outcome may be considered revolutionary for the ceramic community. This will lay a solid ground for dislocation-tuned functional ceramics at room temperature, without the need for high-temperature treatment to potentially save a tremendous amount of energy once scaled up for mass production/processing. This is clear evidence for fundamental research that may lead to new breakthroughs.
Another major achievement is the successful crack suppression framework developed in project MECERDIS, with extension from single crystal to bicrystal materials and polycrystalline samples (first demonstrated on SrTiO3 and MgO in Project MECERDIS), a major step ahead for further extending the materials toolbox. These findings have already been proven helpful using this fundamental defect (dislocation as line defect) for many other potential applications, such as boosting the functional properties, increase the hydrogen production rate, and enhancing the mechanical properties for next-generation functional oxides for the energy transition.
Based on the "Deformation toolbox", the "Materials toolbox" is being extended as well. So far, the most "well-known" plastically deformation ceramics at macroscale at room temperature have been known to be e.g. rock salts, MgO, SrTiO3, with just a very limited total number of them, ever since the first studies dating back to the 1920s. Project MECERDIS has been able to report KTaO3 as the 3rd perovskite oxide to exhibit room temperature bulk plasticity in 2024. This discovery has already generated a huge impact in the ceramic community, considering the 1st one being SrTiO3 was reported in 2001, and the 2nd one being KNbO3 reported in 2016. This breakthrough indeed opens many new doors for Project MECERDIS to extend the materials much more beyond just these 3 materials, using the “alloying” concept borrowed from the metal community, and the outcome may be considered revolutionary for the ceramic community. This will lay a solid ground for dislocation-tuned functional ceramics at room temperature, without the need for high-temperature treatment to potentially save a tremendous amount of energy once scaled up for mass production/processing. This is clear evidence for fundamental research that may lead to new breakthroughs.
Another major achievement is the successful crack suppression framework developed in project MECERDIS, with extension from single crystal to bicrystal materials and polycrystalline samples (first demonstrated on SrTiO3 and MgO in Project MECERDIS), a major step ahead for further extending the materials toolbox. These findings have already been proven helpful using this fundamental defect (dislocation as line defect) for many other potential applications, such as boosting the functional properties, increase the hydrogen production rate, and enhancing the mechanical properties for next-generation functional oxides for the energy transition.
The research outcome of Project MECERDIS is expected to be transformative. So far, its success has been demonstrated not only by the original research output, but more reflected by the scientific communities, including but not limited to the ceramic community, nano-/micromechanics community, etc., for embracing this emerging topic. Nevertheless, this research topic seems to still be in its infancy, and one major challenge still lies in the extremely limited number of materials capable of room-temperature bulk plasticity, and the underlying mechanisms for these already discovered and reported "ductile ceramics" remain elusive. Underpinning such mechanisms, ideally to enable us to predict "ductile ceramics", will be of significant scientific and societal impact. Beyond Project MECERDIS, many research facets centering around "room-temperature plastically deformable ceramics at bulk scale" shall be explored.