The up master of station B @关山口男技术师 released a video of Huazhong University of Science and Technology synthesizing and verifying "LK-99".
The diamagnetic effect (partial levitation) of this crystal can be seen from the video. But according to him, although this crystal has diamagnetism, it is relatively weak, and there is no so-called "zero resistance", and the overall performance is like a semiconductor curve. He believes that even if LK-99 has a superconducting phase, it is still a trace amount of superconducting impurities, which cannot form a continuous superconducting path.
It is said that Wu Hao, a postdoctoral fellow at the School of Materials Science and Technology of Huazhong University of Science and Technology, and Yang Li, a doctoral student, under the guidance of Professor Chang Haixin, successfully verified and synthesized the LK-99 crystal that can be magnetically levitated for the first time. The sample magnetic levitation angle is larger, and it is expected to realize the true non-contact superconducting magnetic levitation.
However, he also mentioned that the team has only verified the Meissner effect at present, because it would destroy the sample to measure the resistance of this sample with a size of only tens of microns.
The Meissner effect is the repulsion of the magnetic field during the phase transition of a superconductor from a general state to a superconducting state. It was discovered by Walter Meissner and Robert Ochsenfeld in 1933. Found when measuring magnetic fields outside superconducting tin and lead samples.
In simple terms, superconductors almost "repel" all the magnetic flux under weak field, so the lines of force cannot penetrate the superconductor, so the conductivity can be regarded as infinite under the Meissner effect, which is a definition of superconductor.
In the presence of a magnetic field, the samples were cooled below their superconducting phase transition temperature. Below the phase transition temperature, the samples cancel out almost all of the magnetic fields inside, and they only detected this effect indirectly.
On the other hand, because superconductors also obey the law of conservation of magnetic flux, when the field inside decreases, the field outside increases. This experiment is the first to demonstrate that superconductors are more than perfect electrical conductors and provides a unique defining property for the superconducting state.
It is worth mentioning that among the major institutions around the world that have reproduced "room temperature superconductivity", only Huazhong University of Science and Technology seems to have achieved partial success.
Last week, Korean researchers published two papers on the preprint platform arXiv, claiming to have discovered the first room temperature ambient pressure superconductor.
Paper Abstract (Translated by DeepL)
Paper 1 ( https://arxiv.org/abs/2307.12008 ):
For the first time in the world, we have successfully synthesized a room-temperature superconductor (Tc over 400 K, 127 oC) working at normal pressure, and its structure is modified lead apatite (LK-99). The critical temperature (Tc), zero resistivity, critical current (Ic), critical magnetic field (Hc) and Meissner effect prove the superconductivity of LK-99. The superconductivity of LK-99 originates from tiny structural deformations caused by slight volume shrinkage (0.48%), rather than external factors such as temperature and pressure. The shrinkage is caused by the substitution of Cu2+ for Pb2+(2) ions in the Pb(2)-phosphate insulating network and creates stress. It is simultaneously transferred to the Pb(1) of the cylindrical pillars, causing the deformation of the cylindrical pillar interface, thereby forming a superconducting quantum well (SQW) at the interface. The heat capacity results show that the new model is suitable for explaining the superconductivity of LK-99. The unique structure of LK-99 allows the tiny twisted structure to be maintained in the interface, which is the most important factor for LK-99 to maintain and exhibit superconductivity at room temperature and ambient pressure.
Paper 2 ( https://arxiv.org/abs/2307.12037 ):
A material named LK-99, which is a modified lead apatite crystal structure with the composition Pb10-xCux (PO4) 6O (0.9<x<1.1), was synthesized using a solid-state method. The material exhibits the ohmic metallic character of Pb(6s1) above the superconducting critical temperature Tc and the suspension phenomenon of the superconductor's Meissner effect at room temperature and atmospheric pressure below Tc. The Tc of the LK-99 sample exceeds 126.85∘C (400 K). According to our analysis, the possible room temperature superconductivity of this material is mainly attributed to two factors: one is the volume shrinkage caused by the insulator-metal transition by substituting copper for lead; the other is the superconductivity at Tc Condensed, one-dimensional (D) chain (Pb2-O1/2-Pb2 along the c-axis) structural deformation enhanced by site-repulsive Coulomb interactions. We discuss the mechanism of room temperature Tc using the one-dimensional BR-BCS theory.
The researchers describe a lead-based copper-doped material LK-99 (representing Pb10-xCux (PO4) 6O), which is obtained by heating the two materials Pb2 (SO4) O and Cu3P in a 1:1 ratio in a vacuum quartz tube to Formed after 925°C. Its manufacturing process is uncomplicated, so labs elsewhere in the world are expected to verify the results and publish the results soon. .
