POLYMER-MATRIX ROUTE TO (BI, PB)2SR2CA2CU3O10+DELTA - THE ROLE OF CA2CUO3

The use of polyethylenimine as active matrix agent has provided a fast synthesis method for (Bi, Pb)2Sr2Ca2Cu3O10+delta, starting from aqueous acetic solutions combined with careful control of the procedural variables. The 110 K phase is obtained as the only superconducting phase after sintering in air during 42 h at 860-degrees-C. This technique yields homogeneously sized, large (ca. 20 mum) platelets of the superconducting material. The presence of an excess of calcium and copper over the stoichiometric requirements accelerates the formation of the superconducting phase. This excess, which appears in the resulting material as Ca2CuO3, influences the superconducting properties, other than T(c), of the bulk material. A maximum in the calculated values of J(c)(T) is found when the molar excess of Ca2CuO3 is approximately 50% of the 110 K phase present.