On the synthesis methodologies to prepare ‘Pb9Cu(PO4)6O’: phase, composition, magnetic analysis and absence of superconductivity

Abstract

Abstract We present the results of our various attempts to prepare the purported room-temperature and ambient-pressure superconducting compound ‘Pb9Cu(PO4)6O’ (LK-99). We experimented with various starting materials and used several synthesis techniques, such as reactions in sealed silica tubes or sintering in air, to prepare the reported phase. Repetition of the exact synthesis procedure reported by Lee et al failed to reproduce the superconducting phase yielding only a multiphase sample. None of our prepared samples exhibit Meissner effect or levitation. Very importantly, only a small amount of copper was detected in the samples of the phase designated ‘LK-99’. Dark gray flakes were found in some samples that reacted to a permanent magnet at room temperature, reminiscing of ‘half-levitation.’ Magnetic measurement reveal that all samples are diamagnetic in the temperature range of 2–325 K. At 2 K, a weak soft ferromagnetic behavior is observed, the origin of which is unknown.