EFFECT OF PRECURSOR PHASE ASSEMBLAGE ON 2223-PHASE-FORMATION AND J(C)IN AG (BI,PB)-2223 TAPES/

The phase evolution and transport properties of Ag/(Bi,Pb)-2223 tapes prepared by PIT process using 'conventional' precursors of six differe nt phase assemblages are studied. The precursors with an initial stoic hiometry of Bi1.8Pb0.4Ca2.2Cu3Oy are prepared by a sol-gel method and samples having different phase assemblages are obtained by changing th e calcination conditions. The dominant phase in all of the precursors is 2212 with varying amounts of secondary phases such as 2201, 2223, C a2PbO4, CuO and Ca7Bi10O22. A wide but systematic variation in J(c) up to about an order of magnitude is found both in the rolled and presse d tapes with respect to the variation in the phase assemblage showing its profound influence on the transport properties of the final tapes. The results are discussed with reference to the role of precursor pha se assemblage on the phase evolution and in-situ growth of oriented 22 23 platelets during the thermo-mechanical treatments. Precursor having high volume fraction of 2212 (50-60%), low 2201 (< 10%) together with Ca2PbO4 (similar to 20%), CuO (similar to 10%), Ca7Bi10O22 (similar t o 5%) and without any 2223 phase is suggested to be a good choice for the fabrication of high J(c) Ag/(Bi,Pb)-2223 tapes. (C) 1998 Elsevier Science B.V.