Diffusion of Nb in Nb-H Alloys

摘要

Self-diffusion coefficient of ~(95)Nb in NbH_x alloys (x=0.05,0.25 and 0.3) has been determined in the temperature range from 823 to 1323 K by using a serial sputter-microsectioning technique. The self-diffusion coefficient of Nb in the NbH_x alloys are larger than that in Nb, suggesting that vacancies are formed by hydrogen dissolution, that is, the formation of hydrogen-induced vacancies. The value of the pre-exponential factor for the Nb diffusion in the NbH_(0.05) alloy is five times larger than that in Nb, while the difference in the activation energies between the NbH_(0.05) alloy and pure Nb is small. The self-diffusion enhancement in the NbH_(0.05) alloy is mainly caused by lowering in vibrational frequencies of atoms in the immediate neighborhood of hydrogen-induced vacancies.