Science: Superconductors!

The startling breakthrough that could change our world

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But in the past year and a half physicists have stumbled on an unusual class of ceramic compounds that change everything. They too must be cooled to become superconductors, but only to a temperature of 98 K (-283 degrees F). And that suddenly brings superconductivity into the range of the practical; liquid helium can be replaced as a coolant by liquid nitrogen, which makes the transition from a gas at the easily produced temperature of 77 K (-320 degrees F). Moreover, liquid nitrogen is cheaper by the quart than milk and so long- lasting that scientists carry it around in ordinary thermos bottles. Also, the & ceramics may be able to generate even more intense magnetic fields than metallic superconductors. Thus, if these new substances can be turned into practical devices -- and most scientists believe they can -- technology will be transformed. Declares Arno Penzias, vice president for research at Bell Labs: "The recent advances in the field of superconductivity are almost without comparison."

Success and celebrity have been a long time in coming to the field of superconductivity. "Until recently," says John Ketterson, a physicist at Northwestern University, "people were glum. There hadn't been a breakthrough in a long time. Funding was drying up. This has sent everyone back into the field with a new burst of enthusiasm." Although Kamerlingh Onnes envisioned early on that his discovery might pave the way for extremely powerful, compact electromagnets, he and other experimenters were stymied by a strange phenomenon: as soon as enough current was flowing through the then known superconductors (lead, tin and mercury, among others) to generate significant magnetic fields, the metals lost their superconductivity.

It was not until the 1950s that scientists discovered alloys, such as niobium tin and niobium titanium, that keep their superconductivity in the presence of intensely strong magnetic fields. And it was not until the '60s and '70s that the manufacture of large superconducting magnets became standardized. But progress toward the other goal of superconductivity researchers, pushing the phenomenon into a practical temperature range, was even slower. By 1973, some 62 years after Kamerlingh Onnes had found superconductivity in mercury at 4.2 K, scientists had upped the temperature to only 23 K, using an alloy of niobium and germanium. After 1973: no improvement.

That was the situation in 1983 when Karl Alex Muller, a physicist at the IBM Zurich Research Laboratory in Switzerland, decided to pursue an approach to superconductivity that had met with limited success in the past. Instead of using the kind of metallic alloys that held the existing record, he turned his attention to the metallic oxides (compounds of metals and oxygen) known as ceramics. Some theorists had suggested ceramics as potential superconductors even though they were poor conductors at room temperatures. In fact, ceramics are often used as insulators-for example, on high-voltage electric- transmission lines.

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