Exploration of superconductivity in LK-99 synthesized under different cooling conditions

The claim of superconductivity above room temperature at ambient pressure in Cu-doped lead apatite (LK-99, Pb_10-xCu_x(PO₄)₆O) has attracted considerable attention. In this paper, we present the results of synthesized LK-99 using a systematic approach based on quenching method variations. A slower cooling rate resulted in an increased LK-99 phase and a decreased Cu₂S phase, with the slowest cooling method achieving the highest concentration of the LK-99 phase. Magnetic levitation was observed in certain specimens, with one end adhering to the magnet and the other end floating, which was distinguished from the Meissner effect. The majority of samples synthesized under different conditions exhibited no response to the magnet. The slowest cooled sample exhibited mostly insulating behavior. The samples synthesized in the other conditions had metallic behaviors, which contained a significant amount of Cu₂S. No evidence of superconductivity was observed within the temperature range of 4 K–300 K in our samples.