Structure changes in (Bi-Pb)-Sr-Ca-Cu-O glass ceramics during the first minutes of crystallization

(Bi0.8Pb0.2)4Sr3Ca3Cu4Ox glasses were prepared by a standard technique of quenching homogenised and melted substrates. The glass-ceramic samples were obtained by annealing of the glass at temperatures between 700 and 850 deg. C. The presence of crystalline phases was studied by X-ray diffraction analysis at room temperature and at the temperature of annealing. Superconducting phases e.g. (Bi0.8Pb0.2)2Sr2Cu1Ox, (Bi0.8Pb0.2)2Sr2CaCu2Ox, (Bi0.8Pb0.2)2Sr2Ca2Cu3Ox and other oxides like Cu2O and CaO were detected. Both scanning electron microscopy and XRD analysis show that during the first 30 min of crystallization the crystalline grains dimensions change from smaller than 0.1 μm to several μm