STRUCTURAL-CHANGES IN PD (RH, PT) SOLID-SOLUTIONS DUE TO HE-3 FORMATION DURING TRITIUM STORAGE

The structural changes induced by He-3 in Pd and Pd-based alloys Pd90R h10 and Pd90Pt10 during tritium storage have been studied by x-ray dif fraction, neutron diffraction, and x-ray absorption. During the first 3 months of aging, the large cell parameter increase can be explained by the formation of finite size defects such as He-3 bubbles, self-int erstitial atoms, and dislocation loops. For longer aging times, the li newidths increase whereas the cell parameter swelling slows down. This can be attributed to the creation of dislocations and dislocation net works. The local order, studied by extended x-ray absorption fine stru cture, is only slightly modified by the presence of He-3 in the solid, which is of particular interest for tritium storage. The Ph substitut ion has only little effects on the structural evolution, whereas the P t substitution favors the formation of finite size defects at the expe nse of dislocations generation. [S0163-1829(98)01017-0].