ABSTRACT
The first of a new family of superconductors, usually known as the high-Tc or cuprate superconductors, was discovered in 1986 by J. G. Bednorz and K. A. Muller. It was a calcium-doped lanthanum cuprate per-ovskite. Cuprates are usually prepared by solid-state reaction of the powdered oxides, carbonates or nitrates of the metals involved, with the cations in the required ratios. The ratios must be accurately controlled, and the reagents must be finely ground and very thoroughly mixed, because the multicomponent phase diagrams usually show competing compounds at nearby compositions. The problems of preparing high-quality samples of cuprate superconductors are very substantial, and although the essential difficulties are well understood, the problems are far from fully solved. Single crystals are most commonly prepared by growth from a flux in a crucible, with extremely slow cooling and subsequent oxygen annealing. Alumina crucibles must be avoided as they contaminate the cuprate.
