Characterisation of Pb2Rh2O7 and Y2Rh2O7: an unusual case of pyrochlore stabilisation under high pressure, high temperature synthesis conditions

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dc.contributor.authorInjac, SDen_AU
dc.contributor.authorMullens, BGen_AU
dc.contributor.authorRomero, FDen_AU
dc.contributor.authorAvdeev, Men_AU
dc.contributor.authorBarnett, Cen_AU
dc.contributor.authorYuen, AKLen_AU
dc.contributor.authorPatino, MAen_AU
dc.contributor.authorMukherjee, Sen_AU
dc.contributor.authorVaitheeswaran, Gen_AU
dc.contributor.authorSingh, DJen_AU
dc.contributor.authorKennedy, BJen_AU
dc.contributor.authorShimakawa, Yen_AU
dc.date.accessioned2024-02-22T00:04:53Zen_AU
dc.date.available2024-02-22T00:04:53Zen_AU
dc.date.issued2024-02-01en_AU
dc.date.statistics2024-02-22en_AU
dc.description.abstractTwo novel oxides with Pb2Rh2O7 and Y2Rh2O7 compositions were synthesised using high pressure, high temperature techniques at 19 GPa and 8 GPa, respectively. Structurally, both compounds were determined to crystallise in the cubic pyrochlore structure, space group Fd[3 with combining macron]m, with no observed oxygen vacancies. Both oxides have effectively identical Rh–O bond lengths of 1.987 Å and a bond-valence sum (BVS) of 4.2 that confirm a Rh4+ oxidation state. Physical property measurements for Pb2Rh2O7 are consistent with a metallic ground state. This is similar to other Pb2M2O7 oxides where M = Ru, Ir, and Os. Y2Rh2O7 represents an unusual case of the lower density (6.356 g cm−3) pyrochlore structure being stabilised under high pressure conditions, while the analogous, higher density (7.031 g cm−3) perovskite YRhO3 is stabilised by synthesis under ambient pressure conditions. The Rh4+ state results in a S = ½ magnetic ground state. Magnetisation measurements suggest strong AFM coupling in Y2Rh2O7. However, long range AFM order is not observed down to 2 K presumably due to the geometric frustration of the pyrochlore lattice. Specific heat and resistivity measurements indicate a large electronic contribution to the heat capacity. The Wilson ratio of 4.78(11) is well above 2, indicating nearness to magnetism and the likely presence of Rh moments in the background of the conduction electrons. Catalytic activity indicated a greater correlation with other Rh pyrochlores as opposed to dependence on the Rh oxidation state. Facebook Twitter LinkedIn YouTube © Royal Society of Chemistryen_AU
dc.description.sponsorshipThe work was partly supported by Grants-in-Aid for Scientific Research (No. 19H05823, 20K20547, 20H00397, 22KK0075, and 23H05457) from MEXT of Japan, and the Advanced International Collaborative Research (AdCORP) Grant No. JPMJKB2304 and Adopting Sustainable Partnerships for Innovative Research Ecosystem (ASPIRE) Grant No. PMJAP2314 by Japan Science and Technology Agency. Brendan J Kennedy and Alex Yuen acknowledge the support from the Australian Research Council, grant number DP190103014 for this work that was facilitated by access to Sydney Analytical, a core research facility at the University of Sydney and was in part undertaken at the Australian Centre for Neutron Scattering. Bryce G. Mullens thanks the Australian Institute for Nuclear Science and Engineering for a PGRA scholarship. Supratik Mukherjee is thankful to DRDO, India, via ACRHEM (DRDO/18/1801/2016/01038: ACRHEMPHASE-III) for financial support, and CMSD, University of Hyderabad, for providing computational facilities. G. Vaitheeswaran would like to acknowledge the Institute of Eminence, University of Hyderabad (UoH-IoE-RC3-21-046) for funding.en_AU
dc.identifier.citationInjac, S. D., Mullens, B. G., Romero, F. D., Avdeev, M., Barnett, C., Yuen, A. K. L., Patino, M. A., Mukherjee, S., Vaitheeswaran, G., Singh, D. J., Kennedy, B. J., & Shimakawa, Y. (2024). Characterisation of Pb2Rh2O7 and Y2Rh2O7: an unusual case of pyrochlore stabilisation under high pressure, high temperature synthesis conditions. Journal of Materials Chemistry C, Advance article. doi:10.1039/D3TC04389Den_AU
dc.identifier.issn2050-7534en_AU
dc.identifier.journaltitleJournal of Materials Chemistry Cen_AU
dc.identifier.urihttp://dx.doi.org/10.1039/d3tc04389den_AU
dc.identifier.urihttps://apo.ansto.gov.au/handle/10238/15377en_AU
dc.identifier.volumeAdvance Articleen_AU
dc.languageEnglishen_AU
dc.language.isoenen_AU
dc.publisherRoyal Society of Chemistry (RSC)en_AU
dc.subjectPyrochloreen_AU
dc.subjectOxidesen_AU
dc.subjectTemperature rangeen_AU
dc.subjectPressure rangeen_AU
dc.subjectPerovskiteen_AU
dc.subjectWilson Loopen_AU
dc.subjectMagnetismen_AU
dc.subjectOxidationen_AU
dc.subjectGround statesen_AU
dc.titleCharacterisation of Pb2Rh2O7 and Y2Rh2O7: an unusual case of pyrochlore stabilisation under high pressure, high temperature synthesis conditionsen_AU
dc.typeJournal Articleen_AU
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