Superconductivity/YBCO

Since the beginning, it has been clear that superconductors with higher critical temperatures would be more useful and practical. The early superconductors with T/sub c/ below 20 K required cooling with liquid helium which boils at a chilly 4.2 K and is quite expensive. If higher temperature superconductors could be found with, say, a T/sub c/ of about 100 K, then they could be cooled with liquid nitrogen, which boils at 77 K and is about 500 times less expensive. The search resulted in several thousand new superconductors between 1911 and 1986. In 1987 C. W. Chu and his colleagues became known as the founders of a superconductor called yttrium barium copper oxide, YBa/sub 2/Cu/sub 3/O/sub 7/ which had a record high transition temperature of 92.5 K. This meant it could be cooled with liquid nitrogen. The author limits the discussion to describing the structure, the properties, and the observed phenomena of YBCO.