[EvaH (OP)]

Casey wants to know:

What superconductor beats silver at room temperature, and what temperature is that? I think Niobium.

What do you think?

[alancalverd]

AFAIK there is no known material that exhibits superconductivity at room temperature, even if we allow that to be as low as 273K, and certainly none that approaches "ordinary refrigeration " temperatures (say up to 230K) at ambient pressures.

That said, silver isn't a superconductor anyway. Pyrolytic graphite can approach the conductivity of silver in the plane of deposition, and the theoretical conductivity of graphene is even higher. 

"Best" superconductor depends on the application: critical temperature, critical field, ductility and malleability, mechanical stability......There's a fair choice of engineering materials that work at 77K (liquid nitrogen is cheap and easy to handle for passive cooling) and others in the range 20 - 70K can be maintained by active gaseous helium cooling systems.

[evan_au]

Room temperature superconductivity is the Holy Grail of superconductor research - the discoverer is certain to get a Nobel Prize.

There are two known classes of superconductor, Type I and Type II, and they have different strengths and weaknesses.
- Type I only function at very low temperatures (< 20K). They turn off suddenly when the temperature gets too high and/or the magnetic field gets too strong.
- Type II can function at higher temperatures, and so are much cheaper to refrigerate. They turn off more gently, and can be used in high-strength magnetic fields, eg MRI machines and the LHC.
See: https://en.wikipedia.org/wiki/Superconductor_classification
https://en.wikipedia.org/wiki/Type-I_superconductor
https://en.wikipedia.org/wiki/Type-II_superconductor

Many years ago, one superconductor researcher observed that the original superconductors worked in 3 dimensions.
- The higher temperature superconductors (at the time) seemed to work in 2 dimensions
- He joked that maybe there are room-temperature superconductors, but they might be 0-dimensional superconductors (ie not very useful for power transmission, for example)
- But a 1-dimensional superconductor might be very useful, if you could find a way to join lengths of it together...

[Penouteniue]

Very interesting, Good job and thanks for sharing such a good blog.