Hydrogen in Ti 2Ni-type intermetallic compounds: a proton NMR study

Abstract

Nuclear magnetic resonance measurements of the proton spin–lattice relaxation rate R 1 for Ti 2Ni-type compounds Ti 2NiH 0.61, Ti 2CoH 0.56, Hf 2FeH 0.59 and Hf 2CoH 0.71 have been performed over the temperature range 20–424 K and the resonance frequency range 13–90 MHz. The experimental results are analyzed to evaluate the electronic (Korringa) contributions to R 1 and the parameters of hydrogen diffusion. The electronic contribution to the relaxation rate in the Ti-based compounds appears to be much higher than that in the Hf-based compounds. The hydrogen mobility is found to increase in the order Ti 2NiH 0.71–Ti 2CoH 0.56–Hf 2FeH 0.59–Hf 2CoH 0.71. The behavior of the proton spin–lattice relaxation rate in Hf 2CoH 0.71 suggests a coexistence of at least two jump processes with different characteristic frequencies.