A NUCLEAR-MAGNETIC-RESONANCE INVESTIGATION OF HYDROGEN DIFFUSION IN THE A15 COMPOUND TI3IR

The spin-lattice relaxation time of hydrogen in Ti3IrHx was determined from pulsed nuclear magnetic resonance measurements carried out between 5 and 630 K (x = 0.55, 3.0 and 3.5; 5 K < T < 630 K). The measured relaxation rates can be described by a superposition of Korringa relaxation and dipolar relaxation due to hydrogen diffusion. The Korringa relaxation times T1,e obey the relation T(1,e)T = 87 +/- 4 s K, 124 +/- 8 s K and 145 +/- 8 s K for x = 0.55, 3.0 and 3.5, respectively. The dipolar relaxation rates were analysed with the help of a modified BPP model, yielding the mean residence times of the hydrogen between about 200 and about 500 K. The mean residence times depend on the hydrogen concentration x. They can be described by an Arrhenius relation with activation energies of 155 +/- 15 meV (for x = 0.55), 365 +/- 30 meV (x = 3.0) and 265 +/- 25 meV (x = 3.5).