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Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062
Hi all. Received kit (Arbor Scientific Economy SC) unfortunately as expected both pellets are in a sorry state.
The less damaged of the two is cracked but looks intact otherwise, the other is in about 50 pieces ranging from 1cm3 to pinhead sized.
How would I go about telling which is which, as I suspect the less cracked one is BSCCO and the disintegrated one is YBCO (Y123) which have distinct properties.
Obviously they will probably need drying out then reannealing in O2 at about 700C with a slow temperature descent but as most of the chemicals are present the anneal should be a lot less demanding than starting from scratch.
In the meantime if anyone wants a piece PM me and I will send one.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
To separate the two could you cool them both below Tc then let all the pieces slowly warm up, some will be affected by a NdFeB magnet, only 10C to 20C margin but may be possible, drop the pieces past the magnet, those that fall are YBCO.
How complicated and expensive is it to get liquid nitrogen? (I have no University to help)
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062
Good plan, thanks for that. Also had an idea to cool them down to say -50C and do an impedance test, the two should show a difference.
EDIT: Works at room temperature, seeing a clear difference between the two ceramics.
The less cracked one looks like BiSrCaCuO and has a very low (3k/10mm) whereas the fragmented one is around 3-400K/10mm possibly YBaCuO as it also has white mottling which is characteristic when exposed to moisture.
This is with a pair of 2mm diameter silver contacts using car demister repair cement. The ceramics are very sensitive to heat which also helps distinguish them and the YBaCuO has a very sharp negative thermal coefficient even sensitive to an infrared 10mm LED putting out just under 200mW at 950nm. No sign of the infamous RTSC phase but I did find out that the paper mentions using a specific wavelength and ultrashort pulses on freshly annealed YBaCuO to see any sort of effect as the superconductor is eseentially opaque to IR otherwise.
Simple sandpaper should work here to expose undamaged surface, and I've attached the pins using Araldite then silvered everything in place as this seems to be stable.
An intriguing idea I did have is to use silicates (ie sodium silicate) mixed with the superconductor to make it more permeable to light allowing the infrared laser light to fully penetrate the material.
Also see may be relevant? Obviously for this to work I'd need to use anhydrous Na2SiO3 or introduce it pre calcining to ensure a permeable matrix is formed.
This compound (yttrium titanate) is easy enough to make and could be a substitute for SrTiO3 yet due to the slight decrease in unit cell and reduction in strain on the boundaries might then allow this metamaterial superconductor idea to work with Y123 or BSCCO.
In this case the modified formula would be around 40% YTiO3 and 60% Y123 or BSCCO layered alternately.
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HTSC repair
