New Materials from High Pressure and Beyond

Lead Research Organisation: University of Edinburgh
Department Name: Sch of Chemistry

Abstract

The discovery of new materials for electronic, magnetic and energy techmology applications motivates much of modern chemistry, physics and materials science. High pressure methods are important for materials synthesis and for inducing new electronic states. This project will explore exciting new materials and also new ideas for materials discovery that go beyond standard high pressure synthesis approaches.

In our high pressure materials syntheses, a chemical reaction is carried out at pressures up to 150,000 atmospheres pressure and temperatures up to 1500C. Afterwards the sample is cooled and then decompressed to ambient conditions. In successful cases, a novel material with a new chemical composition or structure is found to have been 'recovered' from the high pressure and temperature reaction conditions. This is a successful discovery strategy for dense, oxide-based, inorganic materials and will be applied to several specific cases.

Magnetite is the original magnetic material and remains of fundamental interest and of practical importance in new technologies such as spintronic devices. We have recently solved a long-running problem (first identified in 1939) concerning the low temperature electronic structure of magnetite and we discovered unexpected 'orbital molecule' states where electrons are spread over three adjacent iron atoms. In this project we will use high pressure synthesis to recover new chemically-substituted analogues that preserve the essential electronic features of magnetite, in order to discover new 'orbital molecule' states or arrangements. Ruthenium also forms important magnetic oxides such strontium ruthenate which is used in spintronic and silicon thin-film electronics devices. We have recently discovered a new familty of ruthenium oxides, and high pressure will be used to explore their chemical composition range and electronic and magnetic properties.

Oxynitride (oxide-nitride) materials are important for energy technologies as photocatalyts that split water to generate hydrogen, and as phosphors for WLED white-light emitting semiconductor devices. WLED devices are an excellent example of how device innovation (discovery of GaN-based blue LEDs) and materials chemistry (discovery of nitride phosphors) have led to real energy savings on a global scale. We will use a direct high pressure synthesis route to generate new oxynitrides and explore their propeties through collaboration.

The successful preparation of a material is usually the chemical end point for high pressure synthesis, but we will also explore new approaches where a synthesised high pressure material is the starting point for chemical investigations. This can be described as a 'hard-soft' method to generate novel materials by relieving the instability of a dense precursor made under 'hard' high pressure and temperature conditions through 'soft' post-synthesis modification. Recent proof-of-concept results have shown that 'hard-soft' chemistry can generate new transition metal oxides beyond high pressure synthesis. We will also perform high pressure measurements of electronic and magnetic properties of recovered materials to discover electronic properties beyond those at ambient pressure, including very low temperature regimes where quantum mechanical variations are important.

Planned Impact

Both materials and the extreme conditions technologies used to prepare and study them are important to diverse communities. New electronic and magnetic materials have impact from fundamental physics through chemistry and materials science to applications in thin-film devices. Oxynitride ceramics are notable host materials for white-light LED applications. Trained scientists are valuable to the UK economy particularly in the materials sector. Outreach activities featuring electronic materials and extreme conditions are of interest to the public and can prove inspiring to school children.

Discovery of new materials is important to solid state chemists, condensed matter physicists and materials scientists in academia and industry. Electronic and magnetic materials are essential to modern life but our fundamental understanding of the behaviour of correlated electrons that give rise to useful phenomena is still limited. Hence, their experimental exploration remains a very active field with surprising new discoveries made every few years. The impact of such discoveries is initially in the scientific community, but then spreads into the commercial sector. We will collaborate with leading international groups to explore conducting, magnetic (including magnetoresistance and multiferroic) and photoluminescence properties.

Although equipment development is not directly included in this project, the HP measurement activities will help to test new insert technologies being developed by CSEC colleagues. These new methods will have impact in the academic but also industrial research groups studying electronic properties. CSEC is commercialising these cells, and one direct sale has already taken place.

Potential commercialisation of materials synthesis or properties will be investigated by working closely with CSEC's Knowledge Transfer Officer. IP will be protected through patent applications with ERI (Edinburgh Research and Innovation), the University of Edinburgh's research and commercialisation/technology transfer office.

Research results will be disseminated through publication in peer-reviewed journals. We have a strong track record in this respect. Manuscripts will additionally be posted on a free-access archive website of the University of Edinburgh. The travel resources provided by this grant will also provide important dissemination benefits by enabling the PI and RA's to present results at conferences.

This project will have a strong training impact through support for two PDRA's who bring specialist skills in HP science to the UK. As well as gaining training benefits themselves, they will help to train many PhD and Masters students who will receive hands-on training in a wide range of techniques, use of central facility instruments and materials preparation, providing qualified materials scientists for the UK economy.

Results from this project will contribute to CSEC outreach activities that communicate high pressure science and technology to the public. Outreach from this project will principally be through Dr Jenny Rodgers, RSC Regional Coordinator for Scotland, who is actively involved with CSEC and our group. Previous activities have included talks at international science fairs, demonstration of high pressure experiments on Scottish TV, and a highlight in the 'Scotsman' newspaper. Many of these outreach events are aimed at school age children for whom 'elephants in stilettos' ideas of high pressure and demonstrations of a magnet levitated by a superconductor provide an inspiration for future scientific studies and careers.

Publications

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Alonso J (2018) Gérard Demazeau, 07.06.1943-03.11.2017 in Zeitschrift für Naturforschung B

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Araújo B (2020) Spin-phonon coupling in monoclinic BiCrO 3 in Journal of Applied Physics

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Arevalo-Lopez A (2017) Hard-soft chemistry of Sr 1-x Ca x CrO 3-d solid solutions in Materials Chemistry Frontiers

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Arévalo-López AM (2016) Competing antiferromagnetic orders in the double perovskite Mn2MnReO6 (Mn3ReO6). in Chemical communications (Cambridge, England)

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Arévalo-López ÁM (2019) Magnetic frustration in the high-pressure MnMnTeO (MnTeO-II) double perovskite. in Chemical communications (Cambridge, England)

 
Description New magnetoresistive double double perovskites have been synthesised using equipment and methods developed under this award.
Exploitation Route Spintronics sector
Sectors Electronics