SYNTHESIS AND PROCESSING OF BI-DOPED HG1BA2CA2CU3OY SUPERCONDUCTORS

The sequence of reactions that occur during the synthesis of (Hg,Bi)Ba 2Ca2Cu3Oy (HgBi1223) was studied using a series of quenching experimen ts. The formation and decomposition of the intermediate phases during the high temperature reaction were followed as a function of temperatu re. Heat treatment conditions were optimized for the synthesis of pure HgBi1223 phase using commercial BaCaCuO precursor powders. An additio nal lower temperature annealing stage after high temperature reaction is shown to improve the microstructural characteristics of HgBi1223 sa mples. Control of Hg-pressure is shown to be crucial for achieving gra in growth and texture in the final products. A novel approach for the control of HE-pressure during the synthesis of HgBi1223, which consist s of using CaHgO2 as an 'external Hg-source', is demonstrated. Samples synthesized using the new synthesis protocol exhibit improved microst ructural and magnetization properties. (C) 1998 Elsevier Science B.V.