MgB2 Brittle? Superconductor q's & Experiments

[sniffer]

1. is MgB2 brittle? can we draw it like wire and wind it up make a coil/electromagnet with it?

2. liquid nitrogen boils at 77K and freezes at 63K. most superconductor experiments use liquid nitrogen, so does it mean most applications use this temperature range (eg. for squid)? what about those people using liquid nitrogen for mgb2 experiment? use liquid helium?

thanks.

 

[Gokul43201]

This is Zz's area, but so far the questions look pretty straightforward.

1. Yes, I believe MgB2 is fairly brittle. It can not be drawn (forged) into a wire. However, this does not prevent the making of MgB2 wires - the trick is to use a fine powder of MgB2 which is compacted inside a thin tube.

2. Since many of the Cuprate based (eg : YBCO, BSCCO, etc.) HTSCs have Tc above 77K, they are used/studied under liq. nitrogen. MgB2 has its higher Tc at about 45K, and IS hence cooled by liq. Helium, as you guessed.

 

[ZapperZ]

2. liquid nitrogen boils at 77K and freezes at 63K. most superconductor experiments use liquid nitrogen, so does it mean most applications use this temperature range (eg. for squid)? what about those people using liquid nitrogen for mgb2 experiment? use liquid helium?

thanks.

Er... MgB2 has a Tc of 38K. Why would anyone use LN2 for this?

Even for high Tc cuprates, which would have Tc above LN2 temperature, it depends on what you want to use it for. The higher the temperature, the larger the "thermal noise". So for squid application especially, where you may have to detect up to 1 unit flux, you do this at as low of a temperature as you can. But if all one wants is any kind of superconductivity, then using LN2 would be sufficient.

Zz.