LK-99

Common card · No. 221889

LK-99, also called PCPOSOS, is a gray–black (or purple), polycrystalline compound, identified as a copper-doped lead‒oxyapatite. A team from Korea University led by Lee Sukbae (이석배) and Kim Ji-Hoon (김지훈) began studying this material as a potential superconductor in 1999, and in July 2023 published preprints claiming that it acted as a room-temperature superconductor at temperatures of up to 400 K (127 °C; 260 °F) at ambient pressure. Many different researchers attempted to replicate the work, and were able to reach initial results within weeks. By mid-August 2023, the consensus was that LK-99 is not a superconductor at room temperature, and is an insulator in pure form. A number of replication attempts identified non-superconducting ferromagnetic and diamagnetic causes for observations that suggested superconductivity. A prominent cause was a copper sulfide impurity occurring during the proposed synthesis, which can produce resistance drops, lambda transition in heat capacity, and magnetic...

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