Scheifers Jan P, Richardson Adam J D, Lin Hai, Niu Hongjun, Daniels Luke M, Gaultois Michael W, Alaria Jonathan, Robertson Craig M, Claridge John B, Rosseinsky Matthew J
Leverhulme Research Centre for Functional Materials Design, University of Liverpool, Materials Innovation Factory, Liverpool L69 7ZD, United Kingdom.
Department of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, United Kingdom.
Chem Mater. 2025 Apr 23;37(9):3088-3099. doi: 10.1021/acs.chemmater.4c03130. eCollection 2025 May 13.
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 Cu (PO)O that display two distinct compositional ranges differentiated by structural ordering. For > 0.5, we observe substitution in the apatite archetype structure, whereas for < 0.5, we find an apatite superstructure with coupled anion and cation ordering. The 1 × 1 × 2 superstructure in the noncentrosymmetric space group 6̅ (no. 174) for Pb Cu (PO)O with < 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 > 0.5 in Pb Cu (PO)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.
磷灰石是一类重要的矿物基材料家族，具有巨大的化学和结构多样性。最近，它们与标记为LK-99的材料中高温超导性的说法有关，这些材料呈现出含有Pb、Cu、磷酸盐和氧化物成分的复杂相混合物。我们报道了Cu取代的铅磷灰石固溶体Pb₁₋ₓCuₓ(PO₄)₃O，它呈现出由结构有序性区分的两个不同的组成范围。对于x > 0.5，我们观察到在磷灰石原型结构中的取代，而对于x < 0.5，我们发现了具有耦合阴离子和阳离子有序性的磷灰石超结构。对于x < 0.5的Pb₁₋ₓCuₓ(PO₄)₃O，在非中心对称空间群6̅（编号174）中的1×1×2超结构在六边形通道中表现出独特的氧有序模式，并且仅在七个Pb位点中的两个上有选择性的Cu取代。在Pb₁₋ₓCuₓ(PO₄)₃O中x > 0.5时，Cu阳离子被引入到所有Pb位点上，这触发了向典型磷灰石结构的转变，反映了磷灰石骨架的核心结构成分在有序模式中的耦合。
