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Thermal Conductivity of Nearly Stoichiometric Single‐Crystal and Polycrystalline UO 2
Author(s) -
MOORE J. P.,
MCELROY D. L.
Publication year - 1971
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1971.tb12164.x
Subject(s) - condensed matter physics , thermal conduction , thermal conductivity , crystallite , materials science , phonon , scattering , phonon scattering , crystal (programming language) , mean free path , single crystal , antiferromagnetism , chemistry , crystallography , physics , optics , metallurgy , computer science , composite material , programming language
The thermal conductivities, λ, of single‐crystal and polycrystalline UO 2 were measured from 80° to 420°K. The results indicate no observable difference in λ between single‐crystal and polycrystalline UO 2 , and both materials have broad peaks in λ at ∼220°K. The results were used with literature values to determine the effect of closed porosity on λ. The thermal conductivity of theoretically dense UO 2 is described phenomenologically from 80° to 1400°K, where conduction is dominated by the phonon component. The phonon conduction is analyzed by comparison with ThO 2 . This analysis indicates that the high‐temperature λ is limited by 3‐phonon Umklapp scattering processes. Scattering by the disordered spins associated with the paramagnetic U ions contributes a large temperature‐independent phonon scattering term. This mechanism has a mean free path of about 51 Å, which implies that grain boundaries and impurities have a relatively insignificant effect on the phonon conduction far above the antiferromagnetic‐para‐magnetic transition at ∼ 30°K. This implication agrees with the experimental results.