MECHANISM AND KINETICS OF GROWTH OF SUPERCONDUCTING COMPOUND NB3SN

A study has been made of the mechanism and kinetics of formation of Nb3Sn from the elemental components. The Nb3Sn forms partly by diffusion and partly by a solution/ deposition mechanism which depends on thermal gradient mass transfer. The effect of this is to modify the growth equation to x = k t0.36 over the temperature range 950 to 1150° C. The temperature dependence of these two processes, given by the difference between the activation energies for diffusion and solution, is -9.7 kcal/g atom (-0.42 eV/atom) so that the thickness of the Nb3Sn layer produced in any given time decreases with increasing temperature. Various experimental factors are discussed in terms of their influence on the rate of growth of the layer. © 1969 Chapman and Hall.