Meet the material that shrinks when heated

A ceramic material has been created that contracts on heating by over twice as much as the previous record-holder.

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Koshi TakenakaColossal negative thermal expansion in reduced layered ruthenate. The morphology is apparently reversible.

A material that shrinks when heated has been discovered by scientists.

Researchers have formulated a ceramic material consisting of calcium, ruthenium and oxygen atoms that shrinks by 6.7% when it gets hot. This is more than twice as much shrinkage as the previous record holder.

The find may help design industrial systems and equipment that can suffer from repeated expansion over time.

The material studied by scientists at at Nagoya University expands again when it is cooled.

Koshi TakenakaLinear thermal expansion ΔL/Lof reduced layered ruthenates.

The results provide the potential a new class of composite materials that can be used to increase the accuracy of processes and measurements, and to improve the consistent of various devices and extend their lifetimes.

Changing the composition of the material by replacing some of the ruthenium atoms with iron atoms, can control the change in volume as well as the operating temperatures for negative thermal expansion. This window extends to above 200°C for the iron-containing material, which makes it particularly promising for industrial use.

Study co-author Koshi Takenaka said: “The non-uniform changes in the atomic structure seem to deform the microstructure of the material, which means that the voids collapse and the material shrinks.

“This is a new way of achieving negative thermal expansion and it will allow us to develop new materials to compensate for thermal expansion.”

The team recently published a report, ‘Colossal negative thermal expansion in reduced layered ruthenate’ in Nature Communications.

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