Hydrogen, deuterium and tritium in palladium: An eleastic constants study

• Main Authors: Bach, H T, Schwarz, R B, Tuggle, D G
• Format: Conference Proceeding
• Language: English
• Published: United States 01.01.2004
• Subjects: 08 HYDROGEN; AGING; ATOMS; DECAY; DEUTERIUM; EXCITATION; HYDRIDES; HYDROGEN; INTERSTITIALS; MIXTURES; MONOCRYSTALS; PALLADIUM; PHONONS; SHAPE; SHEAR; SPECTROSCOPY; SWELLING; TRITIUM
• ISSN: 1536-1055; 1943-7641

We have used resonant ultrasound spectroscopy to measure the three independent elastic constants of Pd-H, Pd-D, and Pd-T single crystal at 300K as a junction of hydrogen, deuterium, and tritium concentration, respectively. The addition of interstitial H (D, or T) atoms, located at (0, 1/2, 0) in the fcc Pd lattice, affects all three elastic constants C, C{sub 44}, and B. In the mixed (a+{beta}) phase, and with increasing H isotope, the shear modulus C' shows an abnormal softening whereas C{sub 44} and B do not. This is explained in terms of Zener-type anelastic relaxations affecting the shape of the hydride phases in the coherent ({alpha}+{beta}) two-phase mixture In the single {beta}-phase, C' shows a strong isotope dependence whereas C{sub 44} and B show none. This behavior is explained in terms of differences in the excitation of optical phonons. In Pd-T, {sup 3}He is produced by the radioactive decay of tritium. We have measured in situ the swelling and the change in the elastic constants in Pd-T as a function of aging time. Aging ({sup 3}He formation) affects all three elastic constants. These measurements are being used to understand the early stages of {sup 3}H-{sup 3}He clusterformation in aged Pd-T crystal.