Flux Growth of High Temperature Superconductors
19 June 1989
Single crystals are providing key clues to the nature and origin of superconductivity in high T sub c oxides. Common structural features, infinite two-dimensional copper-oxygen planes and layered structures, have been studied in detail in crystals. As is typical for such complex substances, high temperature solution growth techniques are useful for the preparation of bulk single crystals.
A eutectic melt technique has been used for the growth of crystals of the 92K superconductor, Ba sub 2 YCu sub 3 O sub 7, with dimensions approaching 10 x 10 0.1 mm sup 3. Crystal size and morphology are strongly influence by growth conditions, while oxygen stoichiometry can be varied through annealing. The effect of oxygen stoichiometry on various properties of barium yttrium copper oxide such as resistivity and anisotropy will be discussed.
Crystals containing rare earths in place of yttrium have also been grown. Growth conditions are similar to those determined for Ba sub 2 YCu sub 3 O sub 7. These barium rare earth cuprate crystals are superconducting and are of interest for determining the influence of the lanthanoid size on superconducting behavior.