Credit: Arturas Vailionis.

(PhysOrg.com) -- Although materials scientists have theorized for years that a form of super-dense aluminum exists under the extreme pressures found inside a planets core, no one had ever actually seen it. Until now.

A team including researcher Arturas Vailionis of SLAC and Stanford blasted tiny bits of sapphire with a new table-top laser device that penetrates crystals and sets off micro-explosions inside them, creating powerful shock waves that compress the surrounding material. Under these extreme conditions  terapascals of pressure and temperatures of 100,000 Kelvin  warm dense matter forms, the state of matter between a solid and a plasma.

Because sapphire is a form of aluminum oxide, or alumina, researchers expected to find evidence of various phases of high-pressure alumina inside the gem. Instead, they observed minuscule amounts of a surprisingly stable, highly-compressed form of elemental aluminum called body-centered cubic aluminum.

Their results appear in yesterdays edition of Nature Communications. The team included scientists from Australia, Japan, and the Carnegie Institution of Washington.

Vailionis, a researcher with the Geballe Laboratory for Advanced Materials and Stanford Institute for Materials & Energy Sciences, examined the interior of the sapphire and found the novel form of aluminum with a beam of X-ray light from the Advanced Photon Source at Argonne National Laboratory. The laser experiment itself was performed at Shizuoka University in Japan.

High pressure experiments generally are done either with big equipment or with a diamond anvil cell where two diamonds are squeezing a tiny bit of material, but even diamond gives up at a certain point with those pressures, Vailionis said. But this very short pulse of laser light actually ionizes all the material within a very small volume over a short time and creates a plasma which is under enormous pressure and temperature without fracturing the outer shell of the sapphire.

Of particular note, the paper says, is that the team demonstrated that high energy density produced in a simple tabletop experiment makes it possible to form an exotic high-density material phase which could not be produced by other means.

While scientists long have predicted that new classes of materials with unusual combinations of physical properties should exist under extreme pressure and temperature conditions, only hcp-Al, the hexagonal close-packed aluminum phase, had been observed previously. The form made in this experiment is bcc-Al, or body-centered cubic aluminum.

Vailionis said he doesnt expect the research to result in production of new materials in large quantities any time soon, but he believes the equipment used in the experiment offers a new strategy for synthesizing nanoscale amounts of new materials in the laboratory, and opens new possibilities for tabletop research into warm dense matter  the state of matter between a solid and a plasma. Such work could bring scientists a step closer to understanding Earths early history.

Now were thinking about different materials we could use to recreate some of the environments that existed deep in the Earths core when the planet was forming, he said.

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More information: Evidence of Superdense Aluminium Synthesized by Ultrafast Microexplosion, Nature Communications (2011).