Wednesday, 9 August 11:00am – 12:00pm

This seminar will be delivered in Chemistry Lecture Theatre 4 and Online (Zoom) Please email chemistry.researchsupport@sydney.edu.au for zoom link and password.

Speaker: Prof. Paul Attfield, The University of Edinburgh

Host: Dr Kaye Kang

Title: New Materials from High Pressure

Abstract: High pressure methods are important for synthesising new materials, and exploring changes of structure and property in dense matter. New oxide and nitride materials recently synthesized by our group and of interest for electronic and energy applications will be reviewed here. Examples are perovskites with Mn²⁺ at A-sites, such as MnVO₃ [1], the double perovskite Mn₂FeReO₆ [2] and double double perovskites MnRMnSbO₆ and CaMnFeReO₆ with order of A and B site cations [3,4,5]. A remarkable variety of new iron oxides has recently been reported at high pressures, and we have explored the substitutional chemistry of Fe₄O₅. Complex magnetic orders are observed in MnFe₃O₅ [6] and CoFe₃O₅ [7], while CaFe₃O₅ (prepared at ambient pressure) shows electronic phase separation driven by trimeron formation [8]. A new quantum phenomenon, quantised weak ferromagnetism, has recently been discovered in the perovskite YRuO₃ based on the unusual Ru³⁺ state [9]. A high pressure method using sodium azide has recently been developed to synthesise nitrides in high oxidation states giving the iron(IV) nitride, Ca₄FeN₄ [10], an electron-localised Ni²⁺ nitride, Ca₂NiN₂ [11], and a rare example of a nitride perovskite, LaReN₃ [12]. The latter material can be decomposed to give novel reduction products LaReN_2.5 and layered LaReN₂ demonstrating topotactic reduction chemistry analogous to that of perovskite oxides like LaNiO₃ and SrFeO₃.

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2. Arévalo-López A.M., McNally G.M., Attfield J.P. Angew. Chem. 54, 12074 (2015).
3. Solana-Madruga, Á. M. Arévalo-López, et al. Angew. Chem. 55, 9340 (2016).
4. M. McNally, Á. M. Arévalo-López, P. Kearins, F. Orlandi, et al.. Chem. Mat. 29, 8870 (2017).
5. Ji, K. N. Alharbi, E. Solana-Madruga, et al., Angew. Chem. Int. Ed. 2021, 60, 22248.
6. H. Hong, A. M Arevalo-Lopez, M. Coduri, et al. J. Mater. Chem. C 2018, 6, 3271–3275.
7. H. Hong, E. Solana-Madruga, M. Coduri, J. P. Attfield Inorg Chem. 2018, 57 (22), 14347-14352
8. H. Hong, A. M. Arevalo-Lopez, J. Cumby, C. Ritter, J. P. Attfield Nature Commun. 2018, 9, 2975.
9. Ji, A. Paul, E Solana-Madruga, A. M. Arevalo-Lopez, et al. Phys. Rev. Mat. 2020, 4, 091402(R).
10. D. Kloß, A. Haffner, P. Manuel, M. Goto, Y. Shimakawa, J. P. Attfield, Nat. Commun. 2021, 12, 571.
11. D. Kloß, J. P. Attfield, Chem. Commun. 2021, 57, 10427.
12. D. Kloß, M. L. Weidemann, J. P. Attfield, Angew. Chem. Int. Ed. 2021, 60, 22260.

Bio: Paul Attfield holds a Chair in Materials Science at Extreme Conditions at the School of Chemistry and Centre for Science at Extreme Conditions, University of Edinburgh. He received B.A. and D.Phil. degrees from Oxford University, and he was a Co-Director of the Interdisciplinary Research Centre in Superconductivity at the University of Cambridge during 1991-2003. He received the Royal Society of Chemistry’s Meldola and Corday-Morgan medals and Peter Day award, and he was elected a Fellow of the Royal Society in 2014. Early research contributions included pioneering resonant X-ray scattering experiments of cation and valence ordering, and studies of disorder effects in functional oxides. Current research is centred on electronic and magnetic materials including use of high pressure methods.