Critical current density behaviors for sinter-forged Bi-2223 bulks

Bi-2223 bulks were fabricated by a technique, a combination of cold-isostatic-press (CIP) and sinter-forging. Two batches of samples were prepared as presintering was conducted after (Route 1) and before CIP (Route 2). The effects of the deformation rate during sinter-forging, and presintering to critical current density J(c) from exterior and interior sections were investigated. The results revealed that the critical current density of bulks fabricated by Route 1 was much higher than for bulks made by Route 2. The interior section of a sample with higher deformation rate has more contribution to Jc, whereas that with low and too high deformation rate has more equal contribution from exterior and interior sections. Field dependence of critical current density revealed that optimized sinter-forging could improve the critical current density J(c) behavior in external fields, particularly in the low field region below 50 mT, for the samples where CIP was conducted before presintering. For the samples initially pressed with CIP, a higher sinter-forging deformation rate can improve the flux pinning force when the external field is parallel to the sample surface, but degrades the pinning force density when the external fields is perpendicular to the sample surface (H//c, 77 K).