Room Temperature Superconductor
A New Superconductor said to have Zero Electrical Resistance at Room Temperature is Revealed but Scepticism Remains
A new superconductor said to have zero electrical resistance at room temperature is revealed but scepticism remains
Superconductivity is creating a buzz again with the announcement of a new material that is said to have zero electrical resistance at room temperature.
The claim, from researchers in Croatia, comes just a few weeks after the discovery that the simple chemical magnesium diboride superconducts at temperatures up to almost twice those needed for other metallic superconductors to work
The Croatian scientists say that current will flow effortlessly through their material, a mixture of lead carbonate and lead and silver oxides, at up to about 30 °C.
"These results are suggestive of a transition to a superconducting state," says Georg Bednorz of the IBM Zurich Research Laboratory, who shared the 1987 Nobel physics prize for discovering cuprate superconductors.
But because of numerous false alarms in this field, researchers are treating the announcement with caution, especially as no one has yet managed to reproduce the results.
Danijel Djurek, a physicist at A. Volta Applied Ceramics in Zagreb, Croatia, claims that he discovered his superconducting ceramic mixture in the late 1980s. But he was unable to pin down the structure and formula of the material, and his research was interrupted by years of war, following Croatia's split from Yugoslavia. Now Djurek and his team say they have finally hit on a formula that works reliably and reproducibly at room temperature.
Some telltale signs of superconductivity are easy to spot. For example, a graph of resistance plotted against temperature shows a characteristic drop at the temperature at which the material becomes superconducting. Physicists usually require other evidence too, such as the ability to expel all magnetic fields. Djurek's material seems to do this too.
Archie Campbell, director of Cambridge University's Interdisciplinary Research Centre in Superconductivity, says the data clearly shows the hallmark of a superconductor. "This is not a small effect. There's no room for misinterpretation," he says, adding it's either superconductivity or it's a mistake.
Nevertheless, all the researchers contacted by New Scientist were extremely reluctant to start popping corks. "I have some concerns which keep my enthusiasm on a moderate level," says Bednorz.
Do it again
The biggest question mark hangs over the failure of other groups to replicate the results. Paul Chu, director of the Texas Center for Superconductivity at the University of Houston, has been following Djurek's work for some time.
"We recently tried to use his new formula but failed to reproduce his results," says Chu. "I think we will try a little more. It's too important to ignore."
German Patent # 10007915
Material used, e.g., in the Production of a Sputtering Target and as a Superconductor contains Lead, Carbon and Oxygen
Danijel Djurek. et al.
Patent number: DE10007915
Publication date: 2001-09-13
Inventor: DJUREK DANIJEL (HR); MEDUNIC ZVONKO (HR); PALJEVIC MATIJA (HR); TONEJC ANTON (HR)
Applicant: ALCATEL HIGH TEMPERATURE SUPER (DE)
Classification: --- International: C22C11/00; C22C32/00; H01L39/12; C22C11/00; C22C32/00; H01L39/12; (IPC1-7): H01B12/00; C22C5/06; C22C11/00; G01R33/035; H01B1/02; H01B12/10; H01F6/00; H01F27/28; H02K3/02; ---- European: C22C11/00; C22C32/00; H01L39/12C
Application number: DE20001007915 20000221
Priority number(s): DE20001007915 20000221
Abstract: Material contains at least 5 wt.% lead, at least 0.1 wt.% carbon and at least 1 wt.% oxygen and has a specific electrical resistance of not more than 0.5 x 10<-6> Ohm .cm at approximately -79 deg C and/or not more than 1 x 10<-6> Ohm .cm at approximately +20 deg C. Preferred Features: The material further contains Ca, Sr, Ba, Bi, Sb, Hg and Tl.
[ DE10007915 ] ( PDF )