Annealing effects on the modulation structure in the Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O_xsuperconductors

Abstract

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