On the synthesis methodologies to prepare Pb$_9$Cu(PO$_4$)$_6$O -- phase, composition, magnetic analysis and absence of superconductivity

TL;DR

This study attempts to synthesize the purported room-temperature superconductor Pb$_9$Cu(PO$_4$)$_6$O (LK-99) but fails to reproduce superconductivity or detect copper in the phase, suggesting it may not be a superconductor.

Contribution

The paper systematically tests various synthesis methods for LK-99 and finds no evidence of superconductivity or copper presence, challenging prior claims.

Findings

No Meissner effect observed in samples

Copper not detected in the synthesized phase

Samples show diamagnetism and weak ferromagnetism at low temperatures

Abstract

We present the results of our various attempts to prepare the presumably room-temperature and ambient-pressure superconducting compound Pb$_9$Cu(PO$_4$)$_6$O (LK-99). We experimented with various starting materials, and used several synthesis techniques like, sealed quartz tubes and air-sintering pathways to prepare the reported phase. Repetition of the exact synthesis process followed by Lee et al failed to reproduce the superconducting phase yielding only a multiphase sample. None of our prepared samples exhibits Meissner effect or Levitation. Very importantly, no copper (or only a trace amount) could be detected in any of the designated LK-99 phase with PXRD pattern identical to the reported one. Additionally, some dark greyish flakes in some samples responded towards the magnet in a way imitating half-levitation. The magnetic measurement on those sample suggest it is diamagnetic in the measured temperature range of 2-325 K but show a weak soft ferromagnetic behavior at 2 K, the origin of which is still unknown to us.