Much of Joe Ecks' superconducting work is based on taking advantage of planar weight disparity to increase critical temperature.
Joe Eck has experiments where he has gotten YCBO to indicate supercondution at 175K
The discovery of a structure type that facilitates an improvement in the Tc of YBCO beyond 175K. And, while the volume fraction derived from the method of synthesis is low (only a small amount is showing the effect and would need to have purification to make soemthing potentially very useful), the profound Tc improvement again validates planar weight disparity (PWD) as a robust Tc-enhancement mechanism.
PHYSICAL JOURNAL B: How Tc can go above 100 K in the YBCO family
We report the results of the electronic structure calculation of a newly discovered member of the YBCO high-Tc family, i.e., Y3Ba5Cu8O18 (Y358) with Tc > 100, based on the full-potential linearized augmented plane waves method (FP-LAPW) of density functional theory in the generalized gradient approximation (GGA). The evolution of the number of hole carriers in different sites of the CuO2 planes and CuO chains has been investigated in comparison with the other YBCO family members, i.e., Y123, Pr123, Y124, and Y247. The results suggest that pumping hole carriers out of the chains toward the planes enhances the transition temperature. The band structure calculations have been performed for Y358, and the results show similar features with the other family members. Most notably, a van Hove singularity forms near the X point of the Brillouin zone below the Fermi level and within the energy of the buckling phonon mode, for which the interplay is discussed.
YBa2Cu3O7 (Y123) is the first superconductor discovered with the transition temperature above the liquid nitrogen boiling temperature. YBa2Cu4O16
(Y124) and Y2Ba4Cu7O15 (Y247) are other two familiar members of the YBCO-family, but with lower transition temperatures: 84 K and 65 K , respectively.
We have presented here the electronic structure calculations of the newly discovered Y358 compound with Tc > 100 K. The hole content of different sites of its planes and chains has been compared to the other members of the YBCO family. Our results show that in the Y358 system the hole content in four of its five planes increases, and in the other plane which has no apical oxygen the hole content decreases. It is notable that in one of those four planes, the total amount of hole increase puts the plane in the overdoping regime. By comparing the charge differences in the chains, our results imply that in order to have a better superconductor with higher Tc in the YBCOfamily, one should pump more holes from the chains to the planes.
The band structure calculations show similar features with the other YBCO compounds but with a VHS rather far from the Fermi level, which is sensitive to the out-ofplane buckling mode of the oxygen atoms. The discovery of Y358 compound is very promising in finding still better Y-based compounds with higher transition temperature. More investigations are needed experimentally and computationally to better understand how Tc correlates with different structures and with different arrangement of the building blocks of the YBCO family compounds.
Physica C article on the same work
OTHER SUPERCONDUCTING NEWS
Bruker Energy and Supercon Technologies, Inc. (BEST) announced today the completion of its first 1000 meter unit length magnesium diboride (MgB2) superconducting wire, with a strand Je of up to 91 A/mm² at 4.2K and 5T. The MgB2 wire strand is designed to fit into a wire-in-channel superconductor design, focusing on applications in magnetic fields up to 5 Tesla, like clinical or pre-clinical magnetic resonance imaging (MRI) magnets.
Dr. André Aubele, the BEST MgB2 R&D project leader, said: “We have been able to reach state-of-the-art MgB2 performance with our 1000 meter binary MgB2 wire by using magnesium and boron raw materials of industrial quality, which are produced today in quantities of tons. We believe that we can further increase wire performance, especially by using special high quality boron raw material and by optimizing our wire design and production.”
“In order to reach comparable performance and price levels to today’s NbTi wires for MRI systems, further R&D in terms of increased Je performance and manufacturing optimization is necessary. Medium-temperature MgB2 superconductors could then be the material of choice for future generations of liquid cryogen-free MRI magnets operating at temperatures of 10-20 Kelvin without the need for liquid nitrogen or liquid helium cryogens.”