Phase Assemblage in PBSSCO OPIT High‐Temperature Superconductor Precursor Powders – Rietveld Analysis of X‐ray Diffractograms

The phase assemblage in PBSCCO‐2223, (Bi, Pb)₂Sr₂ Ca₂Cu₃O_{10 + x}, precursor powders used for the production of long lengths of superconducting tapes by the oxide powder in tube (OPIT) technology has been determined by Rietveld analysis of powder x‐ray diffractograms. The effects of grain alignment, structure modulation and anisotropic line broadening have been taken into account in the Rietveld analysis. The phase assemblage of the air‐annealed precursor is typically Pb‐free 2212 (Bi, Pb)₂Sr₂CaCu₂O_{8 + x}, Pb₃Sr₃Ca₂CuO₁₂, Ca₂PbO₄, Sr₆Ca₈Cu₂₄O₄₁, and Ca_0.79Sr_0.04CuO₂. If the annealing is done in N₂, the Pb⁴⁺ phases disappear and Pb²⁺ enters the 2212 phase, which is accompanied mainly by Ca₂CuO₃ and CuO. Pb‐2223 formation occurs above 830°C in air.