Nuclear Magnetic Resonance Study of the Diffusion of Hydrogen in Zirconium Hydride

Abstract

Diffusion of hydrogen in two hydrides of zirconium, ZrH_1.54 and ZrH_1.99, has been studied by nuclear magnetic resonance methods. The activation energy for diffusion of hydrogen by a direct tetrahedral to tetrahedral site jump mechanism was found to be 0.54 ev in both compositions. A complex proton line shape was observed in ZrH_1.99 over part of the temperature range covered in these measurements. A tentative explanation of this line shape results in an estimate of 0.65 ev for the activation energy for diffusion by an indirect tetrahedral to octahedral to tetrahedral site mechanism. The rigid lattice linewidth of the proton line in both hydrides was found to be too large to be accounted for by nuclear dipolar broadening.