Patent ID: 7722918
Filing Date: 2010-05-25
Classification: H01L

Abstract:
1. A process for the preparation of high temperature superconducting (HTS) bulk current leads with improved properties, which comprises the steps of: (i) preparing separate water-based solutions of nitrates of Bi, Pb, Sr, Ca and Cu in molar ratio in the range of 1.74 to 1.84:0.34 to 0.4:1.83 to 2.0:1.97 to 2.2:3.0 to 3.13 and then mixing the solutions together to form a single solution; (ii) adding silver in molar ratio of 0.06 to 1.8 in the form of a water-based silver nitrate solution in the single solution (i) to obtain a resultant nitrate solution; (iii) spray drying the resultant nitrate solution obtained in step(ii) to obtain a spray-dried powder; (iv) calcining the spray dried powder to obtain a homogeneous calcined powder; (v) cold isopressing (CIP) of the calcined spray dried powder into a large size tube of length of up to 500 mm, outer diameter up to 150 mm and wall thickness in the range of 2 to 10 mm; (vi) initial sintering of the cold isostatically pressed tube of step (v); (vii) grinding the initially sintered high temperature superconductor (HTS) tube into powder and mixing to obtain a homogeneous initially sintered tube powder; (viii) cold isopressing (CIP) of the said homogeneous initially sintered tube powder obtained in step (vii) into final tubes and rods; (ix) making of grooves at both ends of the said tubes and rods of step(viii); (x) making of a three layer silver metal contact on both end grooves of step (ix); and, xi) co-sintering of the assembly of tubes/rods of step (ix) and the combination of three layer silver metal contacts of step (x), whereby the high temperature superconducting bulk current/leads have a critical current density (Jc) in the range of 366 to 1166 A/cm