Melt Growth of High‐Critical‐Temperature Superconducting Fibers

To determine the intrinsic properties of the newly discovered high‐critical‐temperature oxide superconductors, their single crystals are necessary. Using the float‐zone technique with CO 2 laser heating, coarse‐grained polycrystalline superconducting La‐Sr‐Cu‐O fibers have been grown directly from the melt of a sintered compact. Cu‐O is lost from the liquid and can be compensated by the addition of an excess of CuO in the compact. Superconducting properties (including T c and Meissner effect), X‐ray diffraction, and EDAX indicate that the La/Sr stoichiometry is not maintained from the sintered compact to the melt‐grown material. Attempts to grow an analogous fiber in the Y‐Ba‐Cu‐O system were unsuccessful because the very high evaporation rates of the constituents precluded the maintenance of a molten zone. The results also indicate that patterning of circuits on thin films of the Y‐Ba‐Cu‐O superconductor can be achieved using laser irradiation.