Superconductors.ORG herein reports the observation of superconductivity near 20 C.
In eight magnetization tests a small amount of the compound (Tl5Pb2)Ba2MgCu10O17+ consistently produced sharp diamagnetic transitions (the Meissner effect) near 20 Celsius (see above graphic), and resistive transitions that appeared near 18.5C (see below right). These temperatures are believed accurate +/- 2 degrees.
© SuperconductorsResistance-v-temperature tests of this material were performed using a 4-point probe. Four significant bits of data resolution were necessary to resolve the 18.5C critical transition temperature (Tc) due to a low signal-to-noise ratio (S/N). A sharp transition appeared across just 1.5 uA of a 220 uA signal. This suggests a superconductive volume fraction less than 1% of the bulk.
This extraordinarily high Tc was achieved by engineering a theoretical D223 structure (where D=11 hex) that pushes the limit of the longest C-axis lattice that will superconduct, while simultaneously establishing near-optimum Pb-doping of the Tl-Cu-O blocking layers (see structure at left).
This extraordinarily high Tc was achieved by engineering a theoretical D223 structure (where D=11 hex) that pushes the limit of the longest C-axis lattice that will superconduct, while simultaneously establishing near-optimum Pb-doping of the Tl-Cu-O blocking layers (see structure at left).
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