The pressure dependence of diffusion in the high-temperature body-centered cubic phase of Zr was studied by using radio-tracer techniques. The activation volumes for 95Nb diffusion were equal to 0.161Ω at 1423K and 0.193Ω at 1273K. The small activation volumes indicated a large relaxation of the vacancy. This in turn reflected the inherent weakness, of the body-centered cubic lattice, with regard to shear in the <111> direction. These results (table 343) provided an explanation for the absence of positron trapping in group-IV transition metals.

P.Knorr, J.Jun, W.Lojkowski, C.Herzig: Physical Review B, 1998, 57[1], 334-40

Table 343

Diffusivity of 95Nb in β-Zr