Critical currents in Nb3Ge based pseudobinaries

We have prepared Nb
3
Ge, Nb
3
Ge
1-x
Ga
x
and Nb
3
Ge
1-x
Sn
x
on heated alumina substrates using CVD. Midresistive transitions were up to 21K and transition widths were as low as 0.3K. Critical currents were measured to 22 Tesla at temperatures from 4.2K to 19K. Effective upper critical fields B*
c2
were measured by extrapolating
J\min{c}\max{V2}
vs B data. Preliminary data show that for small Ga additions, B*
c2
increased above the value at x=0. Flux pinning forces vs reduced field b=B/B*
c2
do not obey scaling laws, which we explain as being due to inhomogeneous material having a distribution of T
c
and B
c2
values.