Influence of precursors and synthetic conditions on carbon trapping and related superconducting properties in bulk YBCO

The influences of starting precursors and conditions of densification on carbon retention in YBCO ceramics are investigated. It is shown that both the degree of densification and the kinetics of densification have strong effects on the carbon trapping behaviour. By controlling the densification kinetics, a highly sintered density can be achieved with low carbon trapping in YBCO ceramics. Moreover, one observes that even in a melt-textured sample, depending on the quality of the precursor powders and on the presintering conditions, the residual carbon content can still be high, and depression of the superconducting critical temperature, Tc, may still occur. From a systematic investigation and characterization, we have established a correlation between the superconducting transition characteristics and the residual carbon level. Such a correlation can be used as a guideline for the control of carbon content and the optimization of superconducting properties in YBCO materials.