Formation of Bi(Pb)-2223 with chemically compatible V-rich phase

Abstract Phase assemblage was studied in the samples obtained by thermal treatment of fine nitrate mixtures containing cations of Bi, Pb, Sr, Ca, Cu, and V. Large Bi(Pb)-2223 phase fraction was observed for the initial composition Bi(Pb)-2223+Sr 3 V 2 O 8 . It was found that vanadium-containing surplus resulted in the formation of Sr 3− x Ca x Cu y V 2 O z phase which proved to be chemically compatible with Bi(Pb)-2223, while vanadium solubility in the Bi(Pb)-2223 did not exceed 5 mol%. The new vanadate phase had diffraction pattern different from rhombohedric Sr 3 V 2 O 8 . Composites of Bi(Pb)-2223+ n Sr 2.8 Ca 0.2 Cu 0.3 V 2 O z ( n =0, 0.1, 0.5, 1) were prepared by thermal treatment of the homogeneous precursors at 860°C. In the samples with large vanadium content the formation rate of Bi(Pb)-2223 phase was higher, although the presence of vanadium caused a few degrees T c drop. Low fraction of the vanadate phase in the composite did not influence markedly the sample magnetization at 5, 30 and 77 K, while high fraction of this phase resulted in strong decrease of the hysteresis magnetization at T ≥30 K.