Looking for comparison of superconductors

[jack b]

Hi All

I'm looking for a table of T_cs and normal state resistivities for a selection of 'typical' superconductors. I'm sure such a thing must exist in literature, but I'm having trouble locating it.

Specifically, I've just finished a dissertation project developing a measurement technique to get the T_c of a superconductor. As time was short, we just grabbed the nearest appropriate sample we could, a piece of CeRu₂, and the measurement worked well. I'd like to compare it to other superconductors, to say if my technique would also work on them.

Regards
Jack

 

[f95toli]

For some reason there doesn't seem to be a good table like that, at least that I know of.
There are a few tables in e.g. Tinkham's and Waldram's books but they are fairly small. Tc for normal metals can be found in any table of the elements.

I suspect that part of the problem is that Tc can vary quite a bit even for normal metals depending on the amount of impurities, if it is a film etc (e.g. Tc for bulk aluminium is 1.2K but thermally evaporated aluminium tends to have a Tc of 1.5-1.6K or even higher).
Tc for the high-temperature superconductors dependens on the doping etc.

That said, it would still be good to have a realiably table with the Tc of optimaly doped compounds.


However, if you by "typical superconductors" are referring to "commonly used" there aren't actually that many:
From memory:

Elements: Nb 9.2K, Al 1.2K (1.6K as a film), Pb(7.2K) , In(3.4K)
Allloys: NbTi, NbN (14K), MgB2(39K)
High-Tc: YBCO(92-93K, optimally doped), BSCO-22112 and 2223

These are the ones I could think on the top of my head and I've added Tc for some of them. There are of course many others but I think the list above covers the really common ones.

 

[jack b]

Thanks f95toli, I can get hold of a copy of Tinkham from somewhere, so I'll have a look.

I'll try to explain what I mean by typical:
As a dissertation project, I've built a tunnel diode oscillator to measure the T_c of superconductors. It works by measuring the inductance change in a coil containing a sample.
I tested the system with a piece of CeRu₂, and it worked (with a signal to noise of about 40). If a sample had a lower resistivity than CeRu₂, it would be harder to detect the transition. I'm really looking for a citeable statement like "most superconductors have a normal state resistivity in the range X to Y", so I can justify saying it should work for most superconductor samples.
Of course, what I'm looking for is a minimum normal state resistivity, as those will be harder to measure. I doubt any such number exists, especially once we throw fields and pressures into the mix, so I was looking for a table of examples so I could get a rough guide. To be honest I'd settle for knowing if the resistivity of CeRu₂ was "big" or "small" in context.

I can get resistivites of metals, as you say, but most of the research going on in the group I was working in was with alloys. I guess these are normally more resistive than pure metals? Because (wild guess) the irregular lattice scatters electrons more?

Hope all that made it clearer, not more confusing :-S
Jack

 

[nbo10]

look up Pooles "Handbook of superconduct*" I'm not sure if its superconductors or superconductivity.

You can also look up "CRC Handbook of Chemistry and Physics"

 

[nbo10]

After reading your second post.

Should you be more worried about the surface resistance at the frequency you are driving the coils?

If you do some searching around RSI you should find some similar experiments.

 

[jack b]

Thanks nbo10, I think I can get that book, and it sounds about right.

WRT the surface resistance thing - that's a term I'm not familiar with. Do you mean the resistance when takng the skin depth into account? I'm not operating at a particularly high frequency (10MHz).

Cheers
Jack

 

[nbo10]

Is this an undergraduate dissertation?

What are you measuring, the change in the resonance frequency do to the samples susceptibility or power dissipation caused by the surface resistance?

 

[jack b]

It is, I'm doing an undergrad MPhys. (does that mean it should be in the homework section? if so, my appologies)

I'm measuring the change in susceptibility (which can be explained in terms of the change in skin/penetration depth).

Thanks
Jack