| 摘要 |
To achieve a critical current density jc >/= 800 A/cm<2> in a rotationally symmetrical workpiece of a high temperature superconductor at a temperature of 77 K, a powder mixture (8) having the stoichiometric composition Bi2+xEA3Cu2Oy is used, with -0.15 < x < 0.4; EA = an alkaline earth metal or a mixture of alkaline earth metals, in particular a mixture of Sr and Ca in the ratio Sr:Ca = (2+z):(1-z) with 0 < z < 0.2; 8 </= y </= 8.3. The powder mixture (8) is, at a particle size < 50 mu m, uniformly introduced at room temperature by means of a conveying channel (9) into a silver mould (5) which is arranged within a rotating fusion mould (4) open on one side in a furnace (3). Subsequently the fusion mould (4) is accelerated, heated to 500@C and maintained for about 30 minutes at 500@C. After subsequent partial melting at a temperature of from Tm K to Tm + 6 K, Tm = melting temperature of the pulverulent starting material, for from 30 minutes to 2 hours at an oxygen partial pressure p(O2) >/= 0.8 bar, a first long-term heat treatment at from 840@C to 850@C is carried out for from 20 to 40 hours. A second long-term heat treatment is then carried out at reduced oxygen partial pressure p(O2) and below 700@C, cooling to room temperature in a nitrogen atmosphere. A third long-term heat treatment can follow. <IMAGE> |
