COMPOUNDS OF THE SYSTEM Ba-Pb-Ca-Cu-O. SYNTHESIS AND CRYSTALLOGRAPHIC STUDY *

Mixtures with general chemical type Ba(3-x)PbxCa2Cu3O8+d, (x=0.2, 0.4, …,1.0) were prepared by suitable proportions of BaO, PbO, CaCO3 and CuO. Then crystalline powder samples were obtained by heating in the air, at a temperature of 870 o C, for 36h and then for other 36h. The study of the phase creation and evolution, as a function of the quantity x, has taken place by X-ray diffraction measurements. The crystalline phases were characterized using the PDF2 database. Furthermore, the Powder Profile Analysis (Rietveld’s method) was used for the crystallographic study of the samples and the exact determination of the structures and phase percentages. Seven crystal phases were defined for all the samples, namely BaCuO2, Ba2PbO4, CaO, BaCO3, CaPbO3, Ba2PbCuO6 and CuO, five for each sample. The first three phases are common in all the samples, while the next two are common in the first two samples and the last two are common in the last three samples. Analysis about the morphology of the samples and the concentrations of the elements took place by Scanning Electron Microscopy (SEM).