Kazunori Takada of the National Institute for Materials Science in Ibaraki, Japan, and colleagues started with a compound comprising layers of cobalt oxide with sodium ions sandwiched between them. The team found that when water was added to the mix, the resulting thick layer of sodium ions and water molecules led to superconducting behavior. But although the superconducting properties of the watery cobalt oxide and copper oxide ceramics are quite similar, the temperature at which they perform the trick is not. Whereas copper oxide ceramics remain superconducting to temperatures in the tens of kelvins, the cobalt compound had a critical temperature of 5 kelvins. The scientists say they need further studies to determine the mechanism behind the newly discovered superconductivity, but they hope that the novel material represents a class of superconductors whose properties can be modified by changing the characteristics and spacing of their component layers.
Scientists are continuously on the lookout for new superconductors--materials that conduct electricity perfectly--in the hopes of finding ones that operate at ever-higher temperatures. The first substances found to facilitate resistance-free electron flow did so only at temperatures hovering around absolute zero. The subsequent discovery that certain copper oxide ceramics can superconduct at higher temperatures gave researchers a new avenue to explore. Ever since then, they've been investigating oxides containing metals similar to copper. Superconductive ones have proved elusive, however, until now. According to a report published today in Nature, it seems that some of these oxides should have come with the instructions "to make a superconductor, just add water."