ANNEALING EFFECTS ON THE MODULATION STRUCTURE IN THE BI1.6PB0.4SR2CA2CU3OX SUPERCONDUCTORS

Annealing effects on the modulation structure of Bi1.6Pb0.4Sr2Ca2Cu3Ox superconductors were studied. It was found that upon annealing in flo wing oxygen at 650 degrees C, the modulation structure was changed fro m the pure Pb-type, via the mixed type, finally to the pure Bi-type. W hen the specimen was subjected to sequent annealing in flowing nitroge n at 650 degrees C, the modulation was changed reversibly from the pur e Bi-type via the mixed type to the pure Pb-type. The change in the mo dulation was closely related to the loss or redistribution of Pb ions. The inhomogeneous distribution of Pb ions led to the mixed modulation .