XPS and XRD studies of early stages of crystallisation process in (Bi-Pb)4Sr3Ca3Cu4O x glass-ceramics

(Bi0.8Pb0.2)4Sr3Ca3Cu4O x glass was obtained by a standard technique of quenching melted substrates. As a result of annealing at 850 deg. C the glass crystallised, forming glass-ceramic material. The transformation of the material was studied by X-ray diffraction and X-ray photoelectron spectroscopy. On the basis of the experimental results a consistent picture of the initial stage of the crystallisation of (Bi0.8Pb0.2)4Sr3Ca3Cu4O x glass at 850 deg. C has been proposed. Superconducting phases e.g. (Bi,Pb)2Sr2Cu1O x (Bi,Pb)2Sr2CaCu2O x and other oxides like Ca2PbO4, CuO and CaO were detected. At 850 deg. C, the 2212 phase forms rapidly. On the other hand, the 2201 phase crystallisation occurs mainly at temperatures below 840 deg. C, that is, during heating and cooling stages of annealing. To obtain glass-ceramic material containing mainly 2212 phase, both heating and cooling of the glass should be performed as quickly as possible. Oxygen is incorporated by Ca2PbO4 on the surface and by the 2212 and 2201 phases mostly inside the material. The Ca2PbO4 phase, present on the surface only, does not enhance oxygen diffusion towards the interior part of material