Estimation of AC losses of polycrystalline YBCO by two different methods

AC losses of polycrystalline YBa/sub 2/Cu/sub 3/O/sub y/ were evaluated using AC transport and magnetization techniques. As alternating currents were passed through a cylindrically sintered specimen, effectively resistive voltages were detected by means of a lock-in amplifier and were shown to be linked with AC losses of the specimen. The field dependence of magnetically estimated AC losses for a small chip, synthesized in the same manner, exhibited a plateau region beginning at several tens of oersteds. This field was found to be equal to the self-induced magnetic field created by the DC critical current of the cylindrical specimen and could be attributed to the grain decoupling field. Below this field, the two methods provided almost equivalent AC losses, which also semiquantitatively agreed with theoretical estimation using C.P. Bean's (1962) critical state model.<
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