Hydrogen, Deuterium and Tritium in Palladium: An Elastic Constants Study

• Published in: Fusion science and technology Vol. 48; no. 1; pp. 545 - 550
• Main Authors: Bach, H. T., Schwarz, R. B., Tuggle, D. G.
• Format: Journal Article
• Language: English
• Published: United States Taylor & Francis 01.08.2005
• Subjects: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; AGING; DEUTERIUM; ELASTICITY; EXCITATION; FCC LATTICES; HELIUM 3; HYDRIDES; HYDROGEN; MIXTURES; MONOCRYSTALS; NUCLEAR DECAY; PALLADIUM; PHONONS; RELAXATION; SHEAR; SPECTROSCOPY; SWELLING; TRITIUM; ULTRASONIC WAVES
• ISSN: 1536-1055; 1943-7641
• DOI: 10.13182/FST05-A984

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 function of hydrogen, deuterium, and tritium concentration, respectively. The addition of interstitial H (D, or T) atoms, located at (0,½,0) in the fcc Pd lattice, affects all three elastic constants C', C 44 , and B. In the mixed (α+β) phase, and with increasing H isotope, the shear modulus C' shows an abnormal softening whereas C 44 and B do not. This is explained in terms of Zener-type an elastic relaxations affecting the shape of the hydride phases in the coherent(α+β) two-phase mixture In the single β-phase, C' shows a strong isotope dependence whereas C 44 and B show none. This behavior is explained in terms of differences in the excitation of optical phonons. In Pd-T, 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 ( 3 He formation) affects all three elastic constants. These measurements are being used to understand the early stages of 3 H- 3 He cluster formation in aged Pd-T crystal.