Temperature dependence of the Pd [ital K]-edge extended x-ray-absorption fine structure of PdC[sub [ital x]] ([ital x][similar to]0. 13)

Journal Article · Mon Mar 01 04:00:00 EST 1993 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.47.4873· OSTI ID:6952347

McCaulley, J A ^[1]

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1. Hoechst Celanese Research Division, Robert L. Mitchell Technical Center, 86 Morris Avenue, Summit, New Jersey 07901 (United States)

Pd [ital K]-edge extended x-ray-absorption fine-structure (EXAFS) and x-ray-absorption near-edge-structure (XANES) measurements were performed on a Pd carbide phase, PdC[sub [ital x]] (with [ital x][similar to]0.13), and metallic Pd powder at temperatures between 40 and 423 K. The data were analyzed by nonlinear least-squares fitting using an [ital ab] [ital initio] theoretical standard. The average lattice expansion of the carbide phase, 2.7[plus minus]0.1% relative to Pd metal, agrees well with previous x-ray- and neutron-diffraction results. The temperature dependence of the Pd-Pd nearest-neighbor mean-squared relative displacement ([sigma][sup 2]) yields a Debye temperature, [Theta][sub [ital D]]=295[plus minus]10 K for Pd powder. There is an additional static-disorder contribution in [sigma][sup 2] of 0.0009[plus minus]0.0002 A[sup 2], relative to bulk Pd metal. The Debye temperature of PdC[sub 0.13] powder is also 295[plus minus]10 K. There is, however, an additional static-disorder contribution to [sigma][sup 2] of 0.0012 A[sup 2], relative to Pd powder, probably the result of local distortion of the Pd lattice by interstitial C. The Pd-C coordination is not directly observed in a Fourier transform of the EXAFS. The location of C in octahedral interstices is evident by its effect, through multiple scattering, on the magnitude of the second Pd-Pd peak in the Fourier transform magnitude of the EXAFS data, which is greatly reduced. The Pd [ital K]-edge XANES spectrum of PdC[sub 0.13] is nearly identical to that of Pd metal. There is no significant chemical shift ([le]0.5 eV) of the Pd [ital K] edge of PdC[sub [similar to]0.13].

• DOE Contract Number: FG05-89ER45384; AC02-76CH00016
• OSTI ID: 6952347
• Journal Information: Physical Review, B: Condensed Matter; (United States), Journal Name: Physical Review, B: Condensed Matter; (United States) Vol. 47:9; ISSN PRBMDO; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360602* -- Other Materials-- Structure & Phase Studies
ABSORPTION
CARBIDES
CARBON COMPOUNDS
CHEMICAL COMPOSITION
DEBYE TEMPERATURE
EXPANSION
K ABSORPTION
LATTICE PARAMETERS
PALLADIUM CARBIDES
PALLADIUM COMPOUNDS
SORPTION
TEMPERATURE DEPENDENCE
TRANSITION ELEMENT COMPOUNDS