MICROSTRUCTURE CONTROL IN NB3GE AND ITS EFFECT UPON THE CRITICAL-CURRENT DENSITY

We have investigated the correlations between the critical-current density, Jc, and the microstructure of Nb3Ge films deposited by chemical vapor deposition. Single-phase A15 samples and samples containing Nb5Ge3 particles dispersed in the A15 matrix have been prepared. By growing films of thickness varying in the 103 to 105 A range and multilayered films we controlled the Al5 grain size and the Nb5Ge3 particle size and dispersion. For particle sizes approaching the coherence length of Nb3Ge we have observed an effective flux pinning and very high critical-current densities. We applied our findings to the growth of % 105 X thick films and fabricated layered Nb3Ge tape conductor samples having Jc ~ 105 Acm~2 at 4.2 K and 200 kilogauss. © 1979 IEEE