Anomalously Fast Diffusion of Cobalt inβ-Zirconium: Evidence for Two Different Jump Frequencies from Quasielastic Neutron Scattering

Quasielastic line broadening of neutrons scattered from $\beta$-Zr alloyed with 2 at.% Co indicates that all Co atoms, not merely a small fraction, participate in fast diffusion. At 1100°C the deduced Co jump frequency is about 25 times higher than that of the Zr atoms but about 6 times lower than the Co jump frequency deduced from tracer measurements. This discrepancy and an anomalous decrease in scattering intensity above 1100°C indicate that a second Co jump frequency exists which is several hundred times higher than that of the Zr atoms.