FORMATION OF BI(PB)-2223 WITH CHEMICALLY COMPATIBLE V-RICH PHASE

Phase assemblage was studied in the samples obtained by thermal treatm ent of fine nitrate mixtures containing cations of Pi, Pb, Sr, Ca, Cu, and V. Large Bi(Pb)-2223 phase fraction was observed for the initial composition Bi(Pb)-2223 + Sr3V2O8. It was found that vanadium-containi ng surplus resulted in the formation of Sr3-xCaxCuyV2Oz phase which pr oved to be chemically compatible with Bi(Pb)-2223, while vanadium solu bility in the Bi(Pb)-2223 did not exceed 5 mol%. The new vanadate phas e had diffraction pattern different from rhombohedric Sr3V2O8. Composi tes of Bi(Pb)-2223 + nSr(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 degrees C. In the samples with large vanadium content the formati on rate of Bi(Pb)-2223 phase was higher, although the presence of vana dium 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 stron g decrease of the hysteresis magnetization at T greater than or equal to 30 K. (C) 1998 Published by Elsevier Science B.V. All rights reserv ed.