Comparison of the powder-in-tube processing properties of two (Bi2-xPbx)Sr2Ca2Cu 3O10+δpowders
Abstract
The processing and formation kinetics in air of two commercial
(Bi
2-x
Pb
x
)Sr
2
Ca
2
Cu
3
O
10+
δ
powders (Bi
1.87
Pb
0.34
Sr
1.89
Ca
1.94
Cu
3.00
O
10+
δ
and
Bi
1.84
Pb
0.33
Sr
1.84
Ca
2.07
Cu
3.06
O
10+
δ
) in a silver-sheathed
tape using the powder-in-tube manufacturing technique have been
investigated. The highest concentration of the
(Bi
2-x
Pb
x
)Sr
2
Ca
2
Cu
3
O
10+
δ
phase was found to occur at the ceramic/silver interface. The results over
a range of times and processing temperatures were fitted to an Avrami
equation. In the process range that yielded the optimum volume fraction of
(Bi
2-x
Pb
x
)Sr
2
Ca
2
Cu
3
O
10+
δ
the
Avrami exponent was found to bem=1.2, indicative of platelike
growth. In this same region the critical current densities were found to
be the maximum and showed that if the entire ceramic cross-section can be
processed to have a high volume fraction of the
(Bi
2-x
Pb
x
)Sr
2
Ca
2
Cu
3
O
10+
δ
phase, then critical current densities in excess of 5×10
8
A m
-2
should be routinely achieved. The difference in
physical properties of the two powders was attributed to the different
starting morphologies of the powders, which determined the properties of
the final product.
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