Prediction of the JC (B) Behavior of Bi-2212 Wires at High Field

Bi-2212 wires have been produced for much of the last decade with varying architectures, powder sources, and great variability of final J
_C
(B) properties. As Bi-2212 transitions from an R&D materials development to a magnet technology, means to predictably forecast J
_C
(B) becomes increasingly valuable. Here we report on characterizations of short samples having J
_C
(15 T, 4.2 K) varying from 1210 to 6560 A/mm
²
, measured in fields up to 31 T, and drawn from 10 billets. Using both 4 K transport and variable temperature vibrating sample magnetometer measurements, capable of probing the 20 K irreversibility field, B
_irr
= μ
₀
H
_k
, we found that the vortex pinning properties are very stable across these wires, which all used the same standard powder composition (Bi
_2.17
Sr
_1.94
Ca
_0.89
Cu
_2.00
O
_{8+ x}
), even though it has been made by three different manufacturers over nine years. We conclude that a power-law fit J
_C
∝ B
^-α
, where α = 0.280 (σ = 0.015), works well at 4.2 K over the field range of at least 3-30 T and that μ
₀
H
_k
(20 K) remains stable at 8.6 ± 0.4 T. We conclude that the dominant current limiting mechanism predicting J
_C
(B) in Bi-2212 is the effective filament connectivity. J
_C
(B) at high fields may thus be predicted by simple I
_C
measurements at easily accessible fields in the 3-15 T range.