THE EFFECT OF CALCINATION CONDITIONS ON THE SUPERCONDUCTING PROPERTIES OF Y-BA-CU-O POWDERS

Calcination conditions of the precursor powders, i.e. temperature, typ e of atmosphere and duration, were determined with a view to obtain su perconducting powders with the most advantageous physico-chemical prop erties. Investigated were powders in the Y-Ba-Cu-O system prepared by the sol-gel method. Thermogravimetric examinations of the powders have revealed that the decomposition kinetics of BaCO3 determines the form ation rate of the superconducting YBa2Cu3O7-x ('123') phase. It follow s from the decomposition kinetics of BaCO3 that the process is the mos t intensive in argon, whereas in static air and oxygen it is the slowe st. The phase composition analysis (XRD) and low-temperature magnetic susceptibility measurements of the calcinated powders, confirm the abo ve mentioned changes in the decomposition kinetics. The reaction of ba rium carbonate can be completed if the calcination process is conducte d at the temperature of 850 degrees C for 25 h, yielding easily sinter able powders for obtaining single-phase superconducting bulk samples w ith advantageous functional parameters.