High pressure synthesis in gallium sulphide chalcogenide

Researchers from Universitat Politècnica de València, Universidad de La Laguna, Universidad de Cantabria and the ALBA Synchrotron have published a new work on high pressure chemistry in gallium (III) sulphide chalcogenide. In this work, relevant fingerprints (vibrational and structural) of a pressure-induced paralectric to ferroelectric phase transition are shown. This is the first time when a tetradymite-like (R3m) phase has been synthesized and observed experimentally in gallium-based sequichalcogenides. High pressure X-ray diffraction measurements were carried out at MSPD beamline of ALBA.

Gallium (III) sulphide (Ga2S3) is a compound of sulphur and gallium, that is a semiconductor that has a wide variety of applications in electronics and photonics: nano optoelectronics, photonic chips, electro-catalysis, energy conversion and storage, solar energy devices, gas sensors, laser-radiation detection, second harmonic generation, phase change memories or photocatalytic water splitting systems.

In this work published in Chemistry of Materials,scientists have shown relevant vibrational and structural fingerprints of a pressure-induced paraelectric to ferroelectric R-3m-to-R3m (β’-to-φ) phase transition under decompression on Ga2S3 chalcogenide.

This transition was theoretically predicted in several III−VI B2X3 compounds at high temperature (where B can be aluminium, gallium or indium and X, sulphur, selenium or tellurium). The novelty of this research stems from the synthesis of both phases: β-(R-3m) and α-In2Se3 (R3m)-like structures on Ga2S3 and tuning them via decreasing pressure. Within the III−VI B2X3 compounds, this R-3m-to-R3m (β’-to-φ-Ga2S3) phase transition had been observed experimentally only in the indium (III) selenide (In2Se3)compound, under varying temperature or pressure, to date.

This finding leads the way for designing cheap, nontoxic, nonrare-earth, and abundant element-based devices for second harmonic generation, photocatalytic splitting, ferroelectric, pyroelectric, and piezoelectric applications based on Ga2S3.

Read more on the ALBA website

Image: Samuel Gallego and Catalin Popescu at the MSPD beamline of ALBA.

Scientists synthesise new materials at terapascal pressures for the first time

A team led by the University of Bayreuth (Germany) has synthesized, for the first time, new materials at terapascal pressures, using the ESRF’s ID11 and a unique diamond anvil cell. The results are published in the journal Nature.

Matter changes with variations of pressure and temperature, which allows the tuning of many material properties. These possibilities can shed light onto scientific questions, such as the fundamental understanding of the Universe or lead to targeted design of advanced materials. For example, today super-abrasive cubic Boron Nitride is used for grinding high-quality tool steels and artificial diamonds created using high temperature and high pressure are more prevalent than natural ones.

A team of scientists led by the University of Bayreuth has synthesized new materials at terapascal pressures using laser heating for the first time. The team used rhenium-nitrogen compounds as models to show that studies at pressures three times higher than pressure in the center of the Earth are now possible. Natalia Dubrovinskaya, professor at the University of Bayreuth and one of the corresponding authors of the paper, explains the relevance of these compounds:  “These novel rhenium-nitrogen compounds showed that at ultra-high pressures we can make materials that cannot be made at lower pressures/temperatures, and uncover fundamental rules of physics and chemistry. We found, for example, that due to a huge compression, rhenium behaves chemically in a similar way to iron”.

Read more on the ESRF website

Image: Schematic illustration of the Diamond Anvil Cell assembly

Credit: Timofey Fedotenko

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.”

Read more on the DESY website

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.

Read more on the DESY website

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.

Read more on the DESY website

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