A review in the Journal of Advanced Ceramics gathers the evidence for room-temperature plastic deformation and insists on a distinction the field has been blurring.

Brittleness is the defining liability of ceramics, and it has a specific physical cause. Plastic deformation in a crystalline solid happens when dislocations — line defects in the lattice — move under stress. In ceramics the stress required to move them typically exceeds the stress at which the material fractures, so the crack arrives before the bending does.

A review in the Journal of Advanced Ceramics argues that this is a tendency rather than a law, and assembles the growing body of work in which ceramics deform plastically at room temperature.

The work was done by a team led by Kexin Chen, of the Advanced Structural Ceramics Innovation Center at Ningbo Yongjiang Laboratory and the State Key Laboratory for Advanced Metals and Materials at the University of Science and Technology Beijing, with Zhitong Xu, Jie Zhang, Liran Dong, Yuanwei Chao and Guanghua Liu.

Six routes

The review identifies six mechanisms by which ceramics deform plastically at room temperature: dislocation-mediated plasticity, stress-induced phase transformation, grain-boundary sliding, deformation twinning, interface-mediated deformation, and amorphous flow.

They are not variations on a theme. Dislocation motion is the classical metallic mechanism operating against the odds; stress-induced phase transformation works by the material changing crystal structure under load, which absorbs strain without any dislocation moving; grain-boundary sliding is deformation between crystallites rather than within them; twinning reorients part of the lattice as a mirror image; amorphous flow dispenses with crystallinity altogether in the deforming region.

That diversity is the review’s first point. If plasticity in ceramics arose from one mechanism, it would be a curiosity of particular materials. Six independent routes to the same outcome suggests the behaviour is accessible in principle across the class, through whichever route a given material and microstructure permits.

The review also argues that these mechanisms now appear in bulk and architected ceramics rather than only in microscale experiments — which is the claim that matters for whether any of this becomes useful. Plasticity in a nanoscale pillar compressed inside an electron microscope is a real observation and tells you little about a component, since small samples contain few defects and are not free to crack the way bulk material is.

The distinction the review insists on

The most useful contribution is a piece of conceptual hygiene. The review states that improved fracture toughness does not necessarily imply plasticity, and that nonlinear deformation is not always true irreversible flow.

Both confusions are easy to fall into and common in the literature. A tough ceramic is one that resists crack propagation, usually by mechanisms — fibre pull-out, crack deflection, transformation toughening around a crack tip — that absorb energy without the material deforming plastically anywhere. A stress-strain curve that bends away from a straight line can mean plastic flow, and it can equally mean microcracking, elastic nonlinearity or reversible phase change.

To separate these, the review proposes distinguishing intrinsic plasticity, arising from deformation of the crystal lattice itself, from extrinsic plasticity, arising from grain boundaries, interfaces or engineered architecture.

That division has practical consequences rather than just taxonomic ones. Intrinsic plasticity is a property of the material and travels with it into any shape; extrinsic plasticity is a property of how the material has been assembled, and vanishes if the architecture is changed or damaged. A component designed around the second needs its microstructure preserved through manufacturing in a way that one designed around the first does not.

How to get it

The strategies the review catalogues fall into four groups: defect engineering, structural design, external-field regulation, and nanoscale microstructure design.

Structural design is the most developed, and the listed approaches — coherent interfaces, layered architectures, nanocrystalline structures, crystalline-amorphous composites — share a logic. Each introduces a great many internal boundaries, and boundaries both impede crack propagation and provide sites where deformation can occur without a crack forming.

Defect engineering runs the other way, deliberately introducing lattice defects so that dislocations have somewhere to go at lower stress. External-field regulation is the least conventional: applying electric or magnetic fields during deformation to alter how charged defects move, which is possible in ceramics precisely because their bonding is partly ionic.

What this document is, and is not

The category matters. This is a review — an organising survey of work published by others, with no new experiments. Its value is in the framework and the distinctions, not in any result, and no finding reported here was measured by its authors.

The authors are clear about what remains unresolved: achieving reliable, scalable plasticity in bulk ceramics while retaining high strength and manufacturability.

Each of those three is a genuine obstacle, and the tensions between them are the reason ceramics are still brittle in practice. Strength and plasticity trade against each other in most materials, since the microstructural features that let a material deform also let it yield at lower stress. Manufacturability is the harder constraint: many of the architectures that produce extrinsic plasticity — finely layered composites, controlled nanocrystalline grain sizes — are achievable in a laboratory specimen and not in a turbine blade.

The priorities proposed are correspondingly basic: finding intrinsically plastic ceramic systems, developing scalable fabrication, multiscale design, and pairing experiments with computational modelling. A field whose roadmap still begins with “find materials that do this intrinsically” is at an early stage.

Two notes on the release. It contains no conflicts of interest statement, and while it presents several phrases as the review’s conclusions — that ceramics are capable of irreversible deformation through a variety of mechanisms, that brittleness should no longer be regarded as an unavoidable material property — it does not clearly attribute all of them to a named author, so they are reported here as the review’s framing rather than as anyone’s quoted words.

The paper was published on 21 July 2026. Funding came from the National Key Research and Development Program of China (2025YFF0520903), the National Natural Science Foundation of China (U23A20566 and 52531005), the Natural Science Foundation of Zhejiang Province, the “Pioneer” and “Leading Goose” R&D Program of Zhejiang, the Young Scientists Innovation Team of Zhejiang Province, and the Young Elite Scientists Sponsorship Program of the China Association for Science and Technology.

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Notes

1. “Rethinking brittleness in ceramics: The emergence of room-temperature plasticity.” Journal of Advanced Ceramics, 2026. DOI: 10.26599/JAC.2026.9221353.
2. Tsinghua University Press. “Rethinking brittleness in ceramics: The emergence of room-temperature plasticity.” EurekAlert!, 10 August 2026. https://www.eurekalert.org/news-releases/1139458.

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