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- McRae, Edward, et al.
(författare)
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Raman light scattering and c-axis resistivity evidence for a pressure-induced stage transformation in PdAl2Cl8 intercalated graphite.
- 2000
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 62:20, s. 13757-13766
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Tidskriftsartikel (refereegranskat)abstract
- We have examined several samples of first- to third-stage PdAl2Cl8-intercalated graphite under hydrostatic pressures up to 1 GPa. In stage-1 highly oriented pyrolytic graphite–(HOPG) and single-crystal-graphite-based materials, the c-axis resistivity decreases sharply above a few kilobars; pressure release induces a reversible return to the initial value only in the case of the latter sample. Raman spectra taken in situ under pressure on a HOPG-based material show similarly irreversible effects. Analysis of the spectra taken on higher-stage samples leads to the conclusion that hydrostatic pressure beyond a few kilobars increases the density of the intercalate within the graphitic galleries, transforming the initial sample to a higher-stage material. Since there is no loss of intercalate, the overall intercalate-to-host charge transfer remains constant so that the Raman frequency is approximately the same for both first- and second-stage products. This is an unusual situation in which there is thus an apparent lack of Raman signature in spite of the stage change.
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| 2. |
- Andersson, Odd E., et al.
(författare)
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The c-axis resistivity for two HOPG-based, first stage CuAl2Cl8 and second stage CuCl2 - graphite intercalation compounds as a function of both pressure and temperature
- 1996
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Ingår i: Journal of Physics and Chemistry of Solids, volume 57, issues 6-8. - : Elsevier Ltd.. ; , s. 719-723
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Konferensbidrag (refereegranskat)abstract
- In this paper we present data for the c-axis resistivity of first stage CuAl2Cl8 GIC and second stage CuCl2 GIC as functions of pressure, p, (0.0 < p < 1.5 GPa) and of temperature, T, (4 < T < 300 K). We show evidence of a possible new high-pressure phase above 1.0 GPa for the CuAl2Cl8 GIC and we show that the CuCl2 GIC is very stable at all pressures and temperature investigated. We make a comparison with previous results on SbCl5 GICs and other chloride intercalation compounds and with theories treating the temperature and pressure coefficients of transport parameters in layered solids.
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| 3. |
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| 4. |
- McRae, Edward, et al.
(författare)
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Transport study of (T,p) phase diagram in PdAl2Cl8 intercalated graphite
- 1996
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Ingår i: Journal of Physics and Chemistry of Solids, volume 57, issues 6-8. - : Elsevier Ltd.. ; , s. 827-831
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Konferensbidrag (refereegranskat)abstract
- We have examined the c-direction variations of resistance, Rc (or resistivity, varrhoc) over the 4.2–295 K. temperature range at ambient pressure, and over the 160–295 K range for pressures up to 1.5 GPa on first stage PdAl2Cl8 graphite intercalation compounds. All samples examined manifest a rapid, nonlinear decrease in Rc with pressure (maximum ¦dln Rc/dp¦ > 300 % GPa−1 at 0.4 GPa. The overall Rc decrease is around 90% by 1GPa, a value greater than that observed in any other GIC to date. Upon slow pressure release, the resistance increases linearly but to only about 20–25% of its initial (1 bar) value for HOPG-based materials: on the contrary, it returns along its initial R-p trajectory for GICs based on single crystal graphite. We discuss these data with reference to the X-ray diffraction results, to the significance of the residual resistivity and to studies on other similar lamellar solids.
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