DSC INVESTIGATION OF OXYGEN SUBSYSTEM IN BA-Y-CU-O SUPERCONDUCTORS

DSC investigations have been performed for a series of compounds Ba2YCu3Oy with the oxygen content varying in the range y = 6.0...6.9 by means of various heat treatments at 800-1200 K followed by quenching, or through the chemical extraction of oxygen by placing the sample in dihydrogen at 470-490 K. The sample preserving a constant oxygen content during heating in nitrogen exhibited exothermal effects between 450 and 850 K. It has been shown that the DELTA-H vs. y function reaches maximum at y almost-equal-to 6.5.. Kinetic measurements have shown that the diffusive mobility of oxygen atoms in the lattice is responsible for these effects, viz. the Arrhenius and cooperative processes of reorganization in the non-equilibrium oxygen subsystem of the bulk.