The CrystalStructure of Apatite and Copper-Doped Apatite

Abstract

The recent claim of superconductivity above roomtemperature in Pb_10-xCu_x(PO₄)₆O,where 0.9 < x < 1 (referred to as LK-99), has generated significantinterest. In this study, we first investigated the detailed crystal structuresof four natural apatite by single crystal X-ray diffraction (SXRD) combinedwith a scanning electron microscope (SEM) equipped with energy dispersive X-rayspectroscopy (EDX) measurement. Secondly, pilot experiments of doping copper(Cu) atoms into the apatite lattice were carried out by high-temperature mixedpure copper and natural apatite powders. Finally, copper-doped lead apatite hasbeen synthesized via a three-step solid-state reaction method, and its crystalstructure has been determined using SXRD, SEM/EDX, and transmission electronmicroscopy (TEM).

Keywords

Crystal structure / Apatite / Copper-dopedlead apatite

Supplementary Materials

The following supporting information can be found at: https://www.sciepublish.com/article/pii/510, Figure S1: (a) The Phi360 diffraction pattern of the intermediate Pb₂(SO₄)O, (b) the powder diffraction pattern obtained by integrating the Phi360 diffraction pattern; Figure S2: (a) The Phi360 diffraction pattern of the intermediate Cu₃P, (b) the powder diffraction pattern obtained by integrating the Phi360 diffraction pattern; Figure S3: Scanning electron microscope (SEM) micrographs of single crystal sample of natural fluorapatite sample (A1) purchased from Shi-kong-dui-wang mineral. EDX analysis was performed for various locations as indicated in Table S1; Table S1: The EDX results conducted at every scanning location in the natural fluorapatite sample (A1); Figure S4: Scanning electron microscope (SEM) micrographs of single crystal sample of natural hydroxyapatite sample (A2) purchased from SNQP-yu-he mineral. EDX analysis was performed for various locations as indicated in Table S2; Table S2: The EDX results were conducted at every scanning location in the natural hydroxyapatite sample (A2). Figure S5: Scanning electron microscope (SEM) micrographs of a single crystal sample of natural hydroxyapatite sample (A3) purchased from Jing-hua-shang-mao mineral. EDX analysis was performed for various locations as indicated in Table S3; Table S3: The EDX results conducted at every scanning location in the natural hydroxyapatite sample (A3); Figure S6: Scanning electron microscope (SEM) micrographs of single crystal sample of natural hydroxyapatite sample (A4) purchased from Xun-cheng-kuang-wu mineral. EDX analysis was performed for various locations as indicated in Table S4; Table S4: The EDX results conducted at every scanning location in the natural hydroxyapatite sample (A4); Table S5: Refined atomic coordinates of A1 (fluorapatite purchased from Shi-kong-dui-wang mineral) in the hexagonal P6₃/m (No. 176) structure, extracted from single crystal XRD measurements. The obtained lattice constants are a, b = 9.3849(3) Å and c = 6.8814(3) Å; Table S6: Refined atomic coordinates of A2 (hydroxyapatite purchased from SNQP-yu-he mineral) in the hexagonal P6₃/m (No. 176) structure, extracted from single crystal XRD measurements. The obtained lattice constants are a, b = 9.3654(4) Å and c = 6.8786(3) Å; Table S7: Refined atomic coordinates of A3 (hydroxyapatite purchased from Jing-hua-shang-mao mineral) in the hexagonal P6₃/m (No. 176) structure, extracted from single crystal XRD measurements. The obtained lattice constants are a, b = 9.3731(4) Å and c = 6.8769(3) Å; Table S8: Refined atomic coordinates of A4 (hydroxyapatite purchased from Xun-cheng-kuang-wu mineral) in the hexagonal P6₃/m (No. 176) structure, extracted from single crystal XRD measurements. The obtained lattice constants are a, b = 9.3801(3) Å and c = 6.8748 (3) Å; Figure S7: Scanning electron microscope (SEM) micrographs of single crystal sample of Pb_10−xCu_x(PO₄)₆O-12h. EDX analysis was performed for various locations as indicated in Table S9; Table S9: The EDX results were conducted at every scanning location in the Pb_10−xCu_x(PO₄)₆O-12h sample. Figure S8: Scanning electron microscope (SEM) micrographs of single crystal sample of Pb_10−xCu_x(PO₄)₆O-24h. EDX analysis was performed for various locations as indicated in Table S10; Table S10: The EDX results conducted at every scanning location in the Pb_10−xCu_x(PO₄)₆O-24h sample; Table S11: Refined atomic coordinates of Pb₉Cu(PO₄)₆O in the hexagonal P6₃/m (No. 176) structure, extracted from single crystal XRD measurements by Puphal et al. The obtained lattice constants are a, b = 9.7393(19) Å and c = 7.3953(12) Å. In addition to the above tables and figures, the crystallographic information files, check cif reports, and the crystallographic information sheets for the six phases A1, A2, A3, A4, Pb_10−xCu_x(PO₄)₆O-12h, and Pb_10−xCu_x(PO₄)₆O-24h are also included in the supplementary material.

Acknowledgments

The authors express gratitude to the Fund of National Natural Science Foundation of China (grant No. 52173231; grant No. 51925105), Hebei Natural Science Foundation (grant No. E2022203182), The Innovation Ability Promotion Project of Hebei supported by Hebei Key Lab for Optimizing Metal Product Technology and Performance (grant No. 22567609H) for providing financial support for this study.

Author Contributions

Conceptualization, C.F. and L.Z.; Investigation, Y.L., B.Z., B.W., C.F. and L.Z.; Writing—Original Draft Preparation, Y.L.; Writing—Review & Editing, C.F., B.Z., B.W. and L.Z.; Supervision, C.F.; Funding Acquisition, C.F. and B.W.

Ethics Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data will be made available on request.

Funding

The National Natural Science Foundation of China (grant No. 52173231; grant No. 51925105); Hebei Natural Science Foundation (grant No. E2022203182); The Innovation Ability Promotion Project of Hebei supported by Hebei Key Lab for Optimizing Metal Product Technology and Performance (grant No. 22567609H).

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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