{"title":"Polymorphism of Pb<sub>5</sub>(PO<sub>4</sub>)<sub>3</sub>OH<sub>δ</sub> within the LK-99 mixture.","authors":"Mingyu Xu, Haozhe Wang, Cameron Vojvodin, Jayasubba Reddy Yarava, Tuo Wang, Weiwei Xie","doi":"10.1107/S2052520624010023","DOIUrl":null,"url":null,"abstract":"<p><p>During the synthetic exploration targeting the polycrystalline compound LK-99, an unexpected phase, Pb<sub>5</sub>(PO<sub>4</sub>)<sub>3</sub>OH<sub>δ</sub>, was identified as a byproduct. We elucidated the composition of this compound through single-crystal X-ray diffraction analysis. Subsequent synthesis of the target compounds was achieved via high-temperature solid-state pellet reactions. The newly identified Pb<sub>5</sub>(PO<sub>4</sub>)<sub>3</sub>OH<sub>δ</sub> has an orthorhombic crystal structure with space group Pnma, representing a unique structure differing from the hexagonal apatite phases of Pb<sub>10</sub>(PO<sub>4</sub>)<sub>6</sub>O and Pb<sub>5</sub>(PO<sub>4</sub>)<sub>3</sub>OH. Comprehensive temperature- and magnetic-field-dependent magnetization studies unveiled a temperature-independent magnetic characteristic of Pb<sub>5</sub>(PO<sub>4</sub>)<sub>3</sub>OH<sub>δ</sub>. Solid-state nuclear magnetic resonance spectroscopy was employed to decipher the origins of the phase stability and confirm the presence of hydrogen atoms in Pb<sub>5</sub>(PO<sub>4</sub>)<sub>3</sub>OH<sub>δ</sub>. These investigations revealed the presence of protonated oxygen sites, in addition to the interstitial water molecules within the structure, which may play critical roles in stabilizing the orthorhombic phase.</p>","PeriodicalId":7320,"journal":{"name":"Acta crystallographica Section B, Structural science, crystal engineering and materials","volume":" ","pages":""},"PeriodicalIF":1.3000,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Acta crystallographica Section B, Structural science, crystal engineering and materials","FirstCategoryId":"92","ListUrlMain":"https://doi.org/10.1107/S2052520624010023","RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"CHEMISTRY, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
During the synthetic exploration targeting the polycrystalline compound LK-99, an unexpected phase, Pb5(PO4)3OHδ, was identified as a byproduct. We elucidated the composition of this compound through single-crystal X-ray diffraction analysis. Subsequent synthesis of the target compounds was achieved via high-temperature solid-state pellet reactions. The newly identified Pb5(PO4)3OHδ has an orthorhombic crystal structure with space group Pnma, representing a unique structure differing from the hexagonal apatite phases of Pb10(PO4)6O and Pb5(PO4)3OH. Comprehensive temperature- and magnetic-field-dependent magnetization studies unveiled a temperature-independent magnetic characteristic of Pb5(PO4)3OHδ. Solid-state nuclear magnetic resonance spectroscopy was employed to decipher the origins of the phase stability and confirm the presence of hydrogen atoms in Pb5(PO4)3OHδ. These investigations revealed the presence of protonated oxygen sites, in addition to the interstitial water molecules within the structure, which may play critical roles in stabilizing the orthorhombic phase.
期刊介绍:
Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials publishes scientific articles related to the structural science of compounds and materials in the widest sense. Knowledge of the arrangements of atoms, including their temporal variations and dependencies on temperature and pressure, is often the key to understanding physical and chemical phenomena and is crucial for the design of new materials and supramolecular devices. Acta Crystallographica B is the forum for the publication of such contributions. Scientific developments based on experimental studies as well as those based on theoretical approaches, including crystal-structure prediction, structure-property relations and the use of databases of crystal structures, are published.