High-pressure experiments provide insight into icy planets

Research team determines compression behaviour of water ice in unprecedented detail

An international team of scientists has been using X-rays to take a look inside distant ice planets. At the PETRA III Extreme Conditions Beamline, they investigated how water ice behaves at high pressure, under conditions corresponding to those inside the planet Neptune, for example. At pressures up to almost two million times atmospheric pressure at sea level on Earth, the researchers were able to observe in unparalleled detail how water ice behaves under compression. The team, led by Hauke Marquardt from the University of Oxford, is presenting its findings in the scientific journal Physical Review B.

Planetary ices – such as water ice (H2O), methane ice (CH4) and ammonia ice (NH3) – make up large parts of the ice giants in our solar system and are very likely to occur inside many exoplanets, which are planets outside our solar system. “However, the physical properties and phase diagrams of these compounds are not sufficiently known at the pressures and temperatures that prevail inside planets,” explains Marquardt. “Previous experimental studies using X-ray diffraction in a static diamond anvil cell have contributed a great deal to our understanding of ices at high pressure, but they have been unable to adequately answer numerous questions.”

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Image : Ice at room temperature: A mixture of water ice and liquid water in a high-pressure cell at a temperature around 25 degrees Celsius and a pressure of one gigapascal, which corresponds to 10 000 times atmospheric pressure

Credit: DESY, Hanns-Peter Liermann

Minerals let Earth’s oceans seep down deeper than expected

Amphiboles could carry the volume of the Arctic Ocean into Earth’s mantle in 200 million years

A bigger volume of the world’s oceans is seeping deeper into Earth’s mantle than expected: That is the result of a study investigating a water-bearing mineral abundant in the oceanic crust. High-pressure experiments at DESY’s X-ray source PETRA III show that the mineral glaucophane is surprisingly stable up to 240 kilometres underground, which means it also carries water down to this depth. Scientists attribute this to the gradual cooling of Earth’s interior over geological timescales. The cooler temperatures let glaucophane and possibly other water-bearing minerals survive to greater pressures, as the team headed by Yongjae Lee from Yonsei University in South Korea reports in the journal Nature Communications. The scientists estimate that in about 200 million years, an additional volume equal to the Arctic Ocean could seep deep into Earth’s mantle this way.

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Image: In the high-pressure cell, glaucophane samples are heated and squeezed between two diamond anvils

Credit: Yonsei University, Yoonah Bang/Huijeong Hwang

High-pressure study advances understanding of promising battery materials

X-ray investigation shows systematic distortion of the crystal lattice of high-entropy oxides

In a high-pressure X-ray study, scientists have gained new insights into the characteristics of a promising new class of materials for batteries and other applications. The team led by Qiaoshi Zeng from the Center for High Pressure Science in China used the brilliant X-rays from DESY’s research light source PETRA III to analyse a so-called high-entropy oxide (HEO) under increasing pressure. The study, published in the journal Materials Today Advances is a first, but very important step paving a way for a broader picture and solid understanding of HEO materials.

Modern society requires industry to manufacture efficiently sustainable products for everyday life, for example batteries for smart phones. About five years ago, a new class of materials emerged that appears to be very promising for the design of new applications, especially batteries. These high-entropy oxides consist of at least five metals that are distributed randomly in a common simple crystal lattice, while their crystal structure can be different from each metal’s generic lattice. A popular example of a HEO material consists of 20 per cent each of cobalt, copper, magnesium, nickel and zinc for every oxygen atom, or (Co0.2Cu0.2Mg0.2Ni0.2Zn0.2)O.

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Image: Example of a high-entropy oxide between the anvils of a diamond anvil cell used to exert increasing pressure on the sample. Credit: Center of High Pressure Science, Qiaoshi Zeng