INFLUENCE OF COOLING AND ANNEALING PROCEDURE ON THE INTERGRANULAR COUPLING OF AG-BI2SR2CACU2OX SCREEN-PRINTED TAPE

A study of the influence of the processing conditions of screen-printed ''Bi-2212'' tapes on their intergranular coupling properties, measured by AC susceptibility and DC transport critical current density, has been conducted. Samples have been prepared by melt-solidification and sintering on silver substrates under the same conditions but with different cooling procedures, such as slow cooling, slow cooling and reannealing, rapid cooling and quenching. The cooling rate and the annealing procedure strongly affect not only the superconducting critical temperature, T(c), but also the intergranular coupling properties of the samples. It was found that the T(c) value decreases with a decrease in cooling rate. The reannealing in N2 can improve the T(c) value of the slow-cooled samples. The different cooling procedures lead to the crossover of the field dependence of the AC loss-peak temperature of chi'' characteristics for all investigated samples. The crossover phenomena do not alter the correlation between the transport critical current density, J(c), versus temperature and the AC loss-peak temperature versus AC applied field for the samples in the range of the LN2 temperature (90-65 K), except for the slow-cooled one. The lack of correlation for the slow-cooled sample in this temperature range can be explained by a very significant difference of flux creep between the slow-cooled sample and the rest of the fast-cooled or reannealed samples.