High Pressure Synthesis of All Transition Metal Oxide Perovskites and Related Materials

The search for new electronic and magnetic materials with outstanding properties motivates much of modern chemistry, physics and materials science. The major discoveries of superconducting cuprates and magnetoresistive manganites, plus renewed interests in multiferroics, mixed conductors in fuel cells and batteries, and optoelectronics such as W(hite light)LED phosphors have given rise to worldwide interest in metal oxide-related materials.

This project is centred on perovskites, which are a broad class of materials with structures based on the ABX3 arrangement of the mineral CaTiO3. The inexorable rise of perovskites has been driven by their enormous chemical and structural flexibility and by their outstanding physical and chemical properties, which are often the best in their field, e.g. ferroelectric BaTiO3, YBa2Cu3O7 high-Tc superconductor, (La,Sr)MnO3 and Sr2FeMoO6 CMR (colossal magnetoresistance) for spintronics, multiferroic BiFeO3, mixed conductors such as doped LaCrO3 for fuel cells, molecular perovskites like (CH3NH3)PbI3 for photovoltaic devices. Many of these contain Transition Metals (TM) at the perovskite B-sites.

This project will build on recent developments to explore 'All Transition Metal' (ATM) oxide perovskites where TM's occupy all of the A and B sites in the ABO3 perovskite structure. Proof of concept experiments in the last few years have shown that such materials can be synthesised using high pressure conditions, and some have useful and interesting electronic properties based on TM cation ordering, e.g. a novel switch from negative to large positive magnetoresistances. This project will explore the chemical variety and electronic and magnetic properties of a range of new ATM and related TM-rich oxide perovskites using high pressure synthesis. Pressure is an important variable in materials exploration. We have achieved up to 22 GPa in our two stage press providing an appropriate pressure range to stabilise the ATM oxide perovskites.

Both materials and the extreme conditions methods 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. 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. The specific identified impact areas are:

Materials Impacts
Magnetic materials have a diverse range of applications e.g. for information storage, and much recent research has been devoted to coupling magnetism to other degrees of freedom that enable magnetic switching of electronic phenomena, e.g. magnetoresistive materials for spintronics, multiferroics combining the advantages of ferroelectrics and magnetics, and magnetocalorics for cryogen-free cooling.
Electronic oxides are often used in thin-film devices, and epitaxial film growth also provides a method for growing discovered HP phases at ambient pressure, as illustrated by the example of SrCrO2.8 in the Case document. Collaboration with the Kyoto group through EP/N029119/1 will provide access to Pulsed Laser Deposition facilities for thin film growth.
Silicon oxynitrides have proved to be outstanding phosphor host materials with good thermal stability and are now used in practical white-light WLED devices. Collaboration with the Liu group who work directly with WLED manufacturers will ensure that the commercial potential of new materials is quickly realised.

Technological Impacts
Although equipment development is not directly included in this project, the measurement activities will help to test new HP insert technologies being developed by CSEC colleagues. High pressure cells developed through our Platform project have been sold to central facilities and internationally raising £62k in the last 5 years.

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

Dissemination
Research results will be published in peer-reviewed journals and presented at UK and international conferences. Manuscripts will additionally be posted on an Open Access archive website of the University of Edinburgh. Data generated by this project will be available through the University's DataShare website.

Training Impacts
This project will have a strong training impact through support for the PDRA Dr Arevalo-Lopez who brings specialist skills in HP materials synthesis to the UK. As well as gaining training benefits himself, he will help to train many PhD and Masters students. They will also benefit from the broader training in CSEC. Our students will receive hands-on training in a wide range of techniques, use of central facility instruments and materials preparation, providing qualified individuals to help fill the needs of academia, government and industry.

Outreach
Results from this project will contribute to CSEC outreach activities that communicate high pressure science and technology to the public. We foster outreach to schools and science fairs that are student led and feature demonstrations illustrating high-pressure work. Our press is always of interest during UoE research open days. Members of our research group make strong contributions. Current activities are coordinated by Giuditta Perversi (a PhD student) who was recently awarded UoE's William Darling Memorial Prize in recognition of outstanding contributions to Public Engagement.