Model-Independent Measurements of Hydrogen Diffusivity in the Lanthanum Dihydride-Trihydride System

Journal Article · Thu Jul 01 04:00:00 EDT 1999 · Physical Review Letters

DOI:https://doi.org/10.1103/PhysRevLett.83.340· OSTI ID:355460

Majer, G; Kaess, U ^[1]; Barnes, R G ^[2]

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1. Max-Planck-Institut fuer Metallforschung, Heisenbergstrasse 1, 70569 Stuttgart (Germany)
2. Ames Laboratory, U.S. DOE, and Department of Physics, Iowa State University, Ames, Iowa 50011 (United States)

First model-independent measurements of the hydrogen diffusivity D in lanthanum trihydrides LaH{sub x} (2.00{le}x{le}3.0) have been performed by PFG-NMR. At a fixed concentration x{le}2.92 , D(T) shows single Arrhenius behavior over wide temperature ranges. The activation enthalpy decreases with increasing x from 0.55 (x=2.00) to 0.17thinspthinspeV (x=2.92) , resulting in a strong increase in D . The formation of a hydrogen superstructure associated with the semiconductor-to-metal transition results in a strong reduction in D . It was also observed for the first time that in the stoichiometric limit D depends on the thermal history of the sample. {copyright} {ital 1999} {ital The American Physical Society}

• Research Organization: Ames National Laboratory
• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 355460
• Journal Information: Physical Review Letters, Journal Name: Physical Review Letters Journal Issue: 2 Vol. 83; ISSN 0031-9007; ISSN PRLTAO
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ACTIVATION ENERGY
ARRHENIUS EQUATION
DIFFUSION
ENTHALPY
HYDROGEN
HYDROGEN COMPOUNDS
LANTHANUM COMPOUNDS
LANTHANUM HYDRIDES
NMR SPECTRA
NUCLEAR MAGNETIC RESONANCE
STOICHIOMETRY
TEMPERATURE DEPENDENCE
THERMAL DIFFUSIVITY