Superconductivity observed above freezing point of water
not in 'news'..... This is not the first room temp superconductor observed
Joe Eck's review of the literature may not be spot on in this case, or perhaps his choice of words isn't terribly specific - room temp superconductors have been observed before, but were not stable.
Way back in 87 or 88 some Japanese researches reported a Tc well above room temp with BSCCO in a 1:2:2:1 ratio, pressed into a pellet with some monster press and sintered in O2 at 900C, re-ground, re-pressed & re-sintered ad nauseum in a fashion that only a Japanese metalurgist or Damascus swordsmith could appreciate. I don't remember the journal, but I remember the paper very well.
They put the pellet into their cryostat and affixed leads for their 4-point probe and lock-in amplifier, but measured no resistance before the cooling began. The paper outlined the hilarity as they proceed to tear their equipment apart looking for the problem. They finally decided to test a different sample and observed a +77K Tc as expected. They replaced the odd sample back in the device, and sure enough, zero resistance at room temp. So they warmed the sample to something close to 60C before they observed an expected Tc curve.
This paper reported that repeated observations were made with this sample for months before the Tc began to drop, eventually stabilizing somewhere around a typical oxide SC.
I partially reproduced their results and observed the meissner effect on bulk powders around 30C - for about 15 minutes. The lab I worked in used an interesting technique of binding citrates together in an acetic acid solution to get a good 1:2:2:1 ratio and good distribution at an atomic level, then we'd evaporate off the solution and oxidize the remaining powder. It worked great, but as a result we never had the need for a good press for pellets (all we had was a small bakelite press from an undergrad microscopy lab). I guess the theory was that the mechanical stress of a very tightly packed pellet held some metastable phase in place, until it eventually degraded for whatever reason. The tightly packed pellet lasted for months, my bulk powder sample lasted minutes. It was very intriguing.
Way back in 87 or 88 some Japanese researches reported a Tc well above room temp with BSCCO in a 1:2:2:1 ratio, pressed into a pellet with some monster press and sintered in O2 at 900C, re-ground, re-pressed & re-sintered ad nauseum in a fashion that only a Japanese metalurgist or Damascus swordsmith could appreciate. I don't remember the journal, but I remember the paper very well.
They put the pellet into their cryostat and affixed leads for their 4-point probe and lock-in amplifier, but measured no resistance before the cooling began. The paper outlined the hilarity as they proceed to tear their equipment apart looking for the problem. They finally decided to test a different sample and observed a +77K Tc as expected. They replaced the odd sample back in the device, and sure enough, zero resistance at room temp. So they warmed the sample to something close to 60C before they observed an expected Tc curve.
This paper reported that repeated observations were made with this sample for months before the Tc began to drop, eventually stabilizing somewhere around a typical oxide SC.
I partially reproduced their results and observed the meissner effect on bulk powders around 30C - for about 15 minutes. The lab I worked in used an interesting technique of binding citrates together in an acetic acid solution to get a good 1:2:2:1 ratio and good distribution at an atomic level, then we'd evaporate off the solution and oxidize the remaining powder. It worked great, but as a result we never had the need for a good press for pellets (all we had was a small bakelite press from an undergrad microscopy lab). I guess the theory was that the mechanical stress of a very tightly packed pellet held some metastable phase in place, until it eventually degraded for whatever reason. The tightly packed pellet lasted for months, my bulk powder sample lasted minutes. It was very intriguing.
Giorgio, I'm sorry, I do not. The paper was published in a physics journal in the mid to late 1980's time frame. I no longer have access to the university library, and must pay for articles. The journal articles on scholar.google.com only seem to go back to 1992.
The acetate solution method we used to process the bulk powders used in our re-create is somewhat outlined here: http://www.google.com/patents?hl=en&lr= ... on&f=false
It is a very simple process. The effort in the Japanese paper was based on mixing oxide powders - very slow and cumbersome in comparison.
If you know of an online database that can be accessed by anyone and that goes back to the mid 80's I'd be happy to keep looking.
The acetate solution method we used to process the bulk powders used in our re-create is somewhat outlined here: http://www.google.com/patents?hl=en&lr= ... on&f=false
It is a very simple process. The effort in the Japanese paper was based on mixing oxide powders - very slow and cumbersome in comparison.
If you know of an online database that can be accessed by anyone and that goes back to the mid 80's I'd be happy to keep looking.
Giorgio wrote:@ Gandalf
Do you have any reference literature for the japanese work?
Arxiv link maybe?