Laser technologies have been widely used to process high temperature bulk materials and coatings in planar geometries. Bi-2212 materials show an incongruent melting and the anisotropy that appears during solidification induces a high degree of texture in the annealed samples. We have recently patented a device that combines the use of a laser and a continuous furnace. This system can be used to process planar samples with the laser scanning the sample surface while the material is moving inside the furnace.
The objective of this work is to present a procedure to thermally process superconducting coatings with sizes that can reach values higher than 50 cm². This method entails the use of commercial continuous furnaces that can be easily scaled to any size and allow for uniform sample movement.
In order to reduce the price of the superconducting powders, we have analysed the possibility of using different degrees of reaction in the precursors. Starting from the initial metal compound component mixture, we have performed different heat treatments in a continuous furnace and have determined which is the minimum degree of reaction in these powders that can reach a superconducting sample at the end of the process.
Pressed and substrate-coated precursors were textured using this process. Alumina plates with SrZrO₃ buffer layers were used as substrates. The samples were textured using a laser induced melting zone process within the laser furnace. Samples of 5 or 10 cm width were processed, although the system allows to process samples up to 60 cm width. The influence of several laser parameters in the microstructure of the laser-processed samples was analysed using electron microscopy.
Transport properties were measured after annealing, in particular the temperature dependence of the resistivity and the transport critical current values at 77K. Critical temperature values of the order of 85 K have been obtained and critical current values higher than 200 A/cm-width were measured.