[论文解读] Synthesis of possible room temperature superconductor LK-99:Pb$_9$Cu(PO$_4$)$_6$O

Kapil Kumar, N. K. Karn+1 more|arXiv (Cornell University)|Jul 31, 2023

X-ray Diffraction in Crystallography被引用 14

一句话总结

作者使用两步前驱体法制备 LK-99 类 Pb9Cu(PO4)6O 多晶体并进行 925°C 热处理，但未发现体相室温超导性或抗磁性证据。进一步的热处理研究正在进行中。

ABSTRACT

The quest for room-temperature superconductors has been teasing scientists and physicists, since its inception in 1911 itself. Several assertions have already been made about room temperature superconductivity but were never verified or reproduced across the labs. The cuprates were the earliest high transition temperature superconductors, and it seems that copper has done the magic once again. Last week, a Korean group synthesized a Lead Apatite-based compound LK-99, showing a T$_c$ of above 400$^\circ$K. The signatures of superconductivity in the compound are very promising, in terms of resistivity (R = 0) and diamagnetism at T$_c$. Although, the heat capacity (C$_p$) did not show the obvious transition at T$_c$. Inspired by the interesting claims of above room temperature superconductivity in LK-99, in this article, we report the synthesis of polycrystalline samples of LK-99, by following the same heat treatment as reported in [1,2] by the two-step precursor method. The phase is confirmed through X-ray diffraction (XRD) measurements, performed after each heat treatment. The room temperature diamagnetism is not evidenced by the levitation of a permanent magnet over the sample or vice versa. Further measurements for the confirmation of bulk superconductivity on variously synthesized samples are underway. Our results on the present LK-99 sample, being synthesized at 925$^\circ$C, as of now do not approve the appearance of bulk superconductivity at room temperature. Further studies with different heat treatments are though, yet underway.

研究动机与目标

• 推动对室温超导性的搜索，并重新评估 Pb9Cu(PO4)6O 中的 LK-99 说法。
• 使用报道的两步前驱体法重复合成。
• 在每次热处理后使用 X 射线衍射（XRD）验证相形成。
• 测试室温抗磁性和体超导性指标。
• 在所测试条件下得出是否观察到体超导性的结论。

提出的方法

• 通过两步前驱体法合成 LK-99 型 Pb9Cu(PO4)6O 的多晶体。
• 按照前述报道中引用的相同方案进行热处理。
• 在每次热处理后使用 X 射线衍射（XRD）确认相的形成。
• 测量室温磁性响应以评估抗磁性（如悬浮测试）。
• 评估体超导性的迹象；报告发现及局限。
• 指出正在探索进一步的热处理变化。

实验结果

研究问题

• RQ1 在所测试的合成条件下，Pb9Cu(PO4)6O 是否在室温下呈现体超导性？
• RQ2 在合成样品中是否可检测到室温抗磁性？
• RQ3 经 XRD 在热处理后验证的相纯度如何与任何超导或磁信号相关？
• RQ4 替代的热处理途径能否产生超导证据？

主要发现

• 室温抗磁性未通过磁悬浮测试得到证据。
• 在 925°C 合成的 LK-99 型相不显示体超导性。
• XRD 在每次热处理后均确认相，但未观察到超导转变。
• 作者表示在所测试条件下结果不支持出现体超导性。
• 正在进行使用不同热处理的进一步研究。