Superstructure Formation through Coupled Anion and Cation Ordering in Cu-Substituted Lead Oxyapatites

Scheifers, Jan P, Richardson, Adam JD, Lin, Hai, Niu, Hongjun, Daniels, Luke M ORCID: 0000-0002-7077-6125, Gaultois, Michael W ORCID: 0000-0003-2172-2507, Alaria, Jonathan ORCID: 0000-0001-5868-0318, Robertson, Craig M ORCID: 0000-0002-4789-7607, Claridge, John B ORCID: 0000-0003-4849-6714 and Rosseinsky, Matthew J ORCID: 0000-0002-1910-2483 (2025) Superstructure Formation through Coupled Anion and Cation Ordering in Cu-Substituted Lead Oxyapatites Chemistry of Materials, 37 (9). pp. 3088-3099. ISSN 0897-4756, 1520-5002

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Abstract

Apatites are an important mineral-based material family with huge chemical and structural diversity. They were recently implicated in the claims of high-temperature superconductivity in materials labeled LK-99 that display complex phase mixtures containing Pb, Cu, phosphate, and oxide components. We report Cu-substituted lead apatite solid solutions Pb<inf>10-x</inf>Cu<inf>x</inf>(PO<inf>4</inf>)<inf>6</inf>O that display two distinct compositional ranges differentiated by structural ordering. For x > 0.5, we observe substitution in the apatite archetype structure, whereas for x < 0.5, we find an apatite superstructure with coupled anion and cation ordering. The 1 × 1 × 2 superstructure in the noncentrosymmetric space group P6̅ (no. 174) for Pb<inf>10-x</inf>Cu<inf>x</inf>(PO<inf>4</inf>)<inf>6</inf>O with x < 0.5 exhibits a unique oxygen ordering motif in the hexagonal channels and selective Cu substitution only on two out of seven Pb sites. At x > 0.5 in Pb<inf>10-x</inf>Cu<inf>x</inf>(PO<inf>4</inf>)<inf>6</inf>O, Cu cations are introduced onto all Pb sites, which triggers the transition to the archetypical apatite structure, reflecting the coupling of the core structural components of the apatite framework in the ordering pattern.

Item Type:	Article
Uncontrolled Keywords:	3402 Inorganic Chemistry, 34 Chemical Sciences
Divisions:	Faculty of Science & Engineering Faculty of Science & Engineering > School of Physical Sciences
Depositing User:	Symplectic Admin
Date Deposited:	02 May 2025 15:32
Last Modified:	16 Jun 2026 17:07
DOI:	10.1021/acs.chemmater.4c03130
Open Access URL:	https://doi.org/10.1021/acs.chemmater.4c03130
Related Websites:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3192606
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