It was later discovered that superconducting materials displayed an unusual property of repelling magnetic fields. This discovery, made by Walter Meissner and R. Ochsenfeld, is now known as the "Meissner Effect" and is usually demonstrated experimentally by levitation of a magnet over a superconducting material.
In 1986 IBM research scientists Georg Bednorz and Alex Mü ller announced the discovery of a ceramic material that became superconducting at the (then) unusually high temperature of 30° K. This led to an explosion in the field with researchers scrambling to synthesize new ceramics with higher critical superconducting temperatures. Almost immediately, the critical temperature was raised to 40° K and, under high pressures, ceramics were found that superconducted at 50° K.
In March of 1987 Paul Chu and his coworkers reported a new ceramic made with yttrium-barium-copper oxide that had a critical temperature of about 90° K, a temperature accessible with relatively cheap liquid nitrogen. Soon the critical temperature was again raised, this time to about 125° K.
At this point, visionaries began prophesizing the prospects of a new world full of high-tech marvels developed from the high temperature superconductors. But reality soon came into play. After the dramatic increase of over 100 degrees in the critical temperature in only two years, the advancements came to a screeching halt.
In the past six years the critical temperature has remained at a flat 125° K with only modest and unconfirmed increases. To date, the highest critical temperatures yet recorded have been found in a new class of mercury-based superconducting ceramics that have Tc's exceeding 135 degrees Kelvin. But even as the race for a room temperature superconductor has stalled, a new race has begun in full swing to engineer useful materials out of the brittle ceramic compounds discovered thus far.
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