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December 01, 2008

Superconductor at 212K

Joe Eck at superconductors.org continues his research with superconductors and reports signs of superconductivity over 212K by doping a recently-discovered 200K tin-copper-oxide superconductor with a small amound of indium. The improved formula becomes (Sn5In)Ba4Ca2Cu10Oy. Although the 212K phase forms as a very small volume fraction within the bulk, sharp resistive and diamagnetic transitions are clearly visible when multiple tests are digitally summed together.

Hopefully some better funded research institution will follow up and replicate Joe Eck's work.

Synthesis of these materials was by the solid state reaction method. Stoichiometric amounts of the below precursors were mixed, pelletized and sintered for 36-60 hours at 830C. The pellet was then annealed for 10 hours at 500C in flowing O2.

SnO 99.9% (Alfa Aesar) 4.64 moles
In2O3 99.9% (Alfa Aesar) 0.96 moles
CaCO3 99.95% (Alfa Aesar) 1.38 moles
BaCuOx 99.9% (Alfa Aesar) 5.98 moles
CuO 99.995% (Alfa Aesar) 3.29 moles

The magnetometer employed twin Honeywell SS94A1F Hall-effect sensors with a tandem sensitivity of 50 mv/gauss. The 4-point probe was bonded to the pellet with CW2400 silver epoxy and used 7 volts on the primary.

RESEARCH NOTE: The copper-oxides are strongly hygroscopic. All tests should be performed immediately after annealing.








FURTHER READING
Superconducting News from Joe Eck
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