| 1. |
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| 2. |
- Andersson, Göran, et al.
(författare)
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A high-pressure cell for electrical resistance measurements at hydrostatic pressures up to 8 GPa : Results for Bi, Ba, Ni, and Si
- 1989
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 65:10, s. 3943-3950
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Tidskriftsartikel (refereegranskat)abstract
- A modified Bridgman anvil high-pressure device, capable of producing hydrostatic pressures up to 8 GPa (80 kbar), was designed and built. The size of the pressure chamber (10 mm in diameter) allows the use of large specimens and simple experimental procedures. Experimental results show that hydrostatic conditions are necessary if accurate quantitative information is desired about the electrical properties of materials under pressure. Accurate data on resistance (and resistivity) versus pressure at 294 K are given for Bi, Ba, Ni, and Si. The initial pressure coefficients of R were d(ln R)dP=0.13, −7.6×10−2, −2.0×10−2, and −0.26 GPa−1, respectively. Barium has a resistance minimum near 0.9 GPa. For Bi we observe sharp transitions at 2.55, 2.7, and 7.7 GPa, and for Ba at 5.55 GPa, but we cannot verify the existence of a transition in Ba near 7 GPa. Neither do we confirm the phase transformation in Ni recently reported to occur above 2.5 GPa. For Si, R(P) agrees very well with a theoretical function calculated from the change in band gap and electron mobility with pressure.
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| 3. |
- Andersson, Göran, et al.
(författare)
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Electrical resistivity measurements under hydrostatic conditions up to 10 GPa
- 1984
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Ingår i: Journal de Physique Colloques vol. 45. - : EDP Sciences. - 0449-1947. ; , s. 379-382
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Konferensbidrag (refereegranskat)abstract
- A large scale Bridgman anvil system has been designed. Steel gaskets permit compression of a methanol-ethanol medium over a volume of 500-250 mm3. Up to 12 wires have been used to contact specimens. The system has so far served up to 7.5 GPa, with anvils made of ASP tool steel. The transition Bi III-V was found to occur at a lower pressure than the recommended average. The electrical resistance of copper was measured up to 6 GPa under hydrostatic conditions.
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| 4. |
- Andersson, Göran, et al.
(författare)
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Pressure dependence of the c-axis resistance of stage 2 SbCl5 intercalated graphite to 4 GPa
- 1988
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Ingår i: Solid State Communications. - : Elsevier BV. - 0038-1098 .- 1879-2766. ; 65:7, s. 735-738
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Tidskriftsartikel (refereegranskat)abstract
- The c-axis electrical resistance R has been measured under pressure up to 4 GPa (40 kbar) at room temperature for stage 2, HOPG-based SbCl5 intercalated graphite. In addition to the well known ordering transition at 0.3–0.5 GPa a second anomaly in R is observed above 1 GPa, corresponding to a further phase transition which is not completed until above 2.4 GPa. In all phases R depends more strongly on p for the intercalated material than for HOPG, and the total decrease in R is over 80% to 4 GPa.
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| 5. |
- Andersson, Odd E., et al.
(författare)
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C-axis resistance of HgCl2 intercalated graphite as a function of temperature and pressure
- 1989
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Ingår i: Synthetic Metals volume 34. - Lausanne : Elsevier Sequoia SA. ; , s. 485-490
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Konferensbidrag (refereegranskat)abstract
- The c-axis resistance of stage 3 HgCl2 intercalated graphite has been measured as a function of temperature T and pressure p in the range 40 to 300 K and up to 1 GPa (10 kbar). The absolute resistivity and its T- and p- dependence are all in good agreement with data for other acceptor compounds. The measurements show that a previosly unknown phase transformation occurs above 0.4 GPa. Below 250 K the high pressure phase is metastable down to zero pressure, and an x-ray diffraction analysis of metastable material shows that no stage change occurs. The transition thus probably leads to a different in-plane structure characterized by a more densely packed intercalate layer.
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| 6. |
- Andersson, Odd E., et al.
(författare)
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Structure, c-axis resistivity, and p-T phase diagram of SbCl5 intercalated graphite
- 1989
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Ingår i: Synthetic Metals volume 34. - Lausanne : Elsevier Sequoia SA. ; , s. 187-192
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Konferensbidrag (refereegranskat)abstract
- Experimental data are reported for the c-axis resistivity varrhoc of stages n = 3,4,5 and 8 SbCl5 intercalated graphite as a function of T and p, in the range 40 – 300 K and 0-0.5 GPa (5 kbar). varrhoc varied in a systematic way with p, T, and n. Well ordered low-T phases were obtained for all stages; disordering at 200 – 235 K gave rise to well defined multiple anomalies in varrhoc. We also report x-ray diffraction data on the stage 2 compound: evidence was found for large variations in the in-plane structure even for nominally identical samples.
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| 7. |
- Jacobsson, Per, et al.
(författare)
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Pressure dependence of the thermal and electrical conductivities of the intermetallic compounds AuCu and AuCu3
- 1988
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Ingår i: Journal of Physics and Chemistry of Solids. - : Elsevier BV. - 0022-3697 .- 1879-2553. ; 49:4, s. 441-450
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Tidskriftsartikel (refereegranskat)abstract
- The thermal diffusivity, a, electrical resistivity, ρ, and Seebeck coefficient, S, of ordered and disordered AuCu3 and AuCu have been measured as functions of T and P in the range 100–300 K and 0–2 GPa, and the thermal conductivity, λ, has been calculated from the data for a. The experimental data for ρ agree well with literature data. The ρ dependence of ρ and λ differs significantly between ordered and disordered specimens, but apart from the effect of impurity scattering the disordered materials behave much like the noble metals. For the temperature-dependent part of p (and λ) the P dependence differs by a factor of 2–3 between ordered and disordered states. This is shown to result from the difference in electron band structure, as reflected also in the thermoelectric parameter ξ. The P dependence of the relatively large lattice thermal conductivity of these materials causes the Lorenz ratio L = λρ/T to increase with ρ in all cases.
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| 8. |
- Jacobsson, Per, et al.
(författare)
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Thermal conductivity and electrical resistivity of gadolinium as functions of pressure and temperatur
- 1989
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 40:14, s. 9541-9551
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Tidskriftsartikel (refereegranskat)abstract
- The electrical resistivity ρ and the thermal diffusivity a of gadolinium have been measured as functions of T in the range 45–400 K. The thermal conductivity λ has been calculated from a and experimental data for the specific-heat capacity, cp. λ can be analyzed in terms of simple models for the lattice and electronic components above the Curie temperature TC≃291.4 K. Below TC an additional term, identified as a magnon (spin-wave) thermal conductivity λm, is found. ρ and λ have also been studied as functions of T and P in the range 150–400 K and 0–2.5 GPa. The Lorenz function L=ρλ/T increases by about 20%/GPa under pressure due to a very strong pressure dependence of the lattice thermal conductivity. The pressure coefficients of ρ and λ are -5.1×10-2 and 0.22 GPa-1, respectively, at 300 K (above TC), and 0 and 0.16 GPa-1 at 200 K (below TC). TC and the spin-reorganization temperature Tr≃219 K both decrease under pressure, at the rates -14.0 and -22.0 K/GPa, respectively. Although the magnitude of λm cannot be accurately calculated from the zero-pressure data for λ, the temperature dependence of dλ/dP allows us to distinguish between several models and assign a value of λm≃1.5 W m-1 K-1, or 16.0% of λ, at 200 K.
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| 9. |
- Jacobsson, Per, et al.
(författare)
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Thermal conductivity and Lorenz function of zinc under pressure
- 1988
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Ingår i: International journal of thermophysics. - 0195-928X .- 1572-9567. ; 9:4, s. 577-585
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Tidskriftsartikel (refereegranskat)abstract
- The thermal conductivity lambda and the Lorenz function L of polycrystalline zinc have been calculated from measured values of the thermal diffusivity a and the electrical resistivity gamma as functions of pressure P up to 2 GPa at room temperature. The effects of convection in, and freezing of, the pressure transmitting medium are discussed. Both lambda and L increase with increasing P, with pressure coefficients of 8.7×10–2 and 1.5×10–2 GPa–1, respectively. The volume dependence of L is found to be similar to that found for other simple metals. Data are also given for the Seebeck coefficient S as a function of P and for a(T) and lambda(T) between 55 and 300 K.
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| 10. |
- Jacobsson, Per, et al.
(författare)
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Thermal diffusivity of zinc as a function of pressure and temperature
- 1985
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Ingår i: High Temperatures - High Pressures Vol. 17. - London : Pion Press. - 0 85086 124 1 ; , s. 103-109
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Konferensbidrag (refereegranskat)abstract
- The thermal diffusivity and the electric resistivity of polycrystalline zinc have been measured as functions of temperature between 90 and 480 K at atmospheric pressure, and as functions of pressure up to 2 GPa (20 kbar) at room temperature. The pressure and temperature dependence of the thermal conductivity has been calculated by using literature data for the specific heat capacity. No minimum was found in the thermal conductivity at low temperatures. The pressure coefficient of the thermal conductivity was found to be 4.1 x 10-2 /GPa, which indicates that the Lorenz function of zinc decreases with increasing pressure.
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| 11. |
- Jarlborg, Thomas, et al.
(författare)
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Electron-Phonon Interaction of fcc and dhcp La under Pressure
- 1987
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Ingår i: Japanese Journal of Applied Physics, volume 26, Supplement 26-3-2. - : The Japan Society of Applied Physics. ; , s. 919-920
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Konferensbidrag (refereegranskat)abstract
- The pressure dependence of the electron-phonon interaction of La has been studied for both phases by two methods: One is a calculation of λ and the other uses the calculated plasma frequency and the measured temperature and pressure dependence of the electrical resistivity. These results as well as a calculation of the spin-fluctuation contribution suggest that quenching of spin-fluctuations with pressure contribute to the increase of Tc with pressure in La.
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| 12. |
- Jarlborg, Thomas, et al.
(författare)
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Resistivity, bandstructure and superconductivity of DHCP and FCC La under pressure
- 1989
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 1:44, s. 8407-8424
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Tidskriftsartikel (refereegranskat)abstract
- Electronic and superconducting properties of DHCP and FCC La are studied both by measurements of the electrical resistance as a function of temperature and pressure and by calculations of the band structure, Fermi surface properties and the electron-phonon interaction lambda . The importance of a hydrostatic environment for reliable resistance measurements is stressed. The transport properties of both phases are similar with small and negative values of the pressure coefficient of resistance. In contrast, the band structure calculations show large differences between the two phases, particularly in the pressure dependence, e.g. of the density of states (DOS) and the plasma frequency. Two new remarkable properties of La have been found, adding to previously known anomalies. One is a strong temperature dependence of the pressure coefficient of resistance which decreases with increasing temperature in both phases. The other is a strong pressure dependence of the plasma frequency in the FCC phase, which is larger than in any other element known to us. From these results the pressure dependence of lambda is obtained by two independent methods for each phase. For FCC, both methods give d ln lambda /dp=0.05+or-0.02 GPa-1, while for DHCP, a decrease of lambda with pressure or an almost pressure independent lambda is suggested. These results cannot fully explain the observed Tc(p) in the FCC phase and fail completely in the DHCP phase. The contribution from spin fluctuations is calculated approximately and found to account qualitatively for this discrepancy. In particular, the DOS decreases slowly with pressure in the FCC phase which gives some decrease of the spin fluctuation contribution in this phase, while in the DHCP phase the DOS decreases strongly, leading to suppression of the spin fluctuations under pressure.
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| 13. |
- Lundberg, Bo, et al.
(författare)
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Basal plane resistivity and phase diagram of HNO3 intercalated graphite in the range 130–320 K and 0–1.6 GPa
- 1986
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Ingår i: Solid State Communications. - : Elsevier Science Ltd.. - 0038-1098 .- 1879-2766. ; 58:10, s. 747-751
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Tidskriftsartikel (refereegranskat)abstract
- The basal plane resistivity varrho of stages 3–5 HNO3 intercalated graphite has been measured as a function of temperature T and pressure p in the range 130–320 K and 0–1.6 GPa (16 kbar). A contactless method was used. The phase boundary of the 250 K ordering transition at zero pressure was traced up to 320 K through the corresponding anomaly in varrho. The pressure dependence of varrho was strongly stage dependent, such that for stages 3, 4 and 5 the observed pressure coefficients (1/varrho)dvarrho/dp were approximately 0.08, −0.08, and −0.22 GPa−1, respectively, near zero pressure.
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| 14. |
- Lundberg, Bo, et al.
(författare)
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Pressure-dependent electrical conductivity of polypyrrole
- 1985
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Ingår i: Molecular Crystals and Liquid Crystals vol. 118. - : Informa UK Limited. - 0026-8941. ; , s. 155-158
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Konferensbidrag (refereegranskat)abstract
- The results of pressure dependent electrical conductivity measurements in polypyrrole are consistent with a simple extension of the variable-range-hopping model of electronic transport in disordered media.
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| 15. |
- Lundberg, Bo, et al.
(författare)
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Pressure effects on electrical conductivities in intercalated graphite and doped polypyrrole
- 1984
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Ingår i: Journal de Physique Colloque vol. 45. - : EDP Sciences. - 0449-1947. ; , s. 213-216
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Konferensbidrag (refereegranskat)abstract
- We have measured the pressure dependence up to 2.5 GPa of the electrical resistance of the acceptor intercalated graphites CnFeCl3, CnSbF5, and CnHNO3. The slope of resistance versus pressure is approximately the same in all cases. Two different types of high pressure transitions are observed in CnSbF5 and CnHNO3. The results of electrical resistance measurements under pressure in polypyrrole are consistent with a simple extension of the variable-range-hopping model. We infer for this material that the density of states at the Fermi level increases with pressure.
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| 16. |
- Lundberg, Bo, et al.
(författare)
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Resistivity of a composite conducting polymer as a function of temperature, pressure, and environment: Applications as a pressure and gas concentration transducer
- 1986
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 60:3, s. 1074-1079
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Tidskriftsartikel (refereegranskat)abstract
- The resistivity of a commercial carbon-filled composite conducting polymer (ET-Semicon[large-closed-square]) has been measured as a function of temperature between 80 and 400 K and under pressure up to 1.5 GPa (15 kbar). Large changes in resistivity were observed. The resistivity was also very sensitive to the presence of certain solvents and hydrocarbons. The results are explained as percolation effects caused by changes in volume due to pressure, thermal expansion, or dissolved solvents. The material studied is found to have a wide range of potential applications for pressure measurements and as a transducer for gas or liquid concentration.
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| 17. |
- Neve, Jesper, et al.
(författare)
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Electron band structure, resistivity, and the electron-phonon interaction for niobium under pressure
- 1983
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Ingår i: Physical Review B Condensed Matter. - : American Physical Society. - 0163-1829 .- 1095-3795. ; 28:2, s. 629-637
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Tidskriftsartikel (refereegranskat)abstract
- Accurate measurements of the electrical resistance of Nb are presented as a function of temperature and pressure in the region 0-40°C and 0-1 GPa. From these measurements and published results for the compressibility and the pressure dependence of the superconducting transition temperature Tc we evaluate the pressure dependence of the electron-gas plasma frequency ω(p). The electronic structure of Nb is calculated from a self-consistent linear muffin-tin orbital method and results are obtained for the pressure dependence of the density of states at the Fermi surface, the root mean square over the Fermi surface of the Fermi velocity, the optical mass, and the plasma frequency. The experimental and calculated results for the pressure dependence of ω(p) are both close to dlnω2 / dlnV=-1.9. This agreement suggests that measurements of the electrical resistance as a function of temperature and pressure provide a new test of band-structure calculations. From our measurements of the resistance and calculations of ω(p) and from published results for the compressibility we obtain the pressure dependence of the electron-phonon interaction λ(p). With p given in gigapascals, the result is dlnλ / dp=-0.0047.
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| 18. |
- Rapp, Östen, et al.
(författare)
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The pressure dependence of of the electron-phonon interaction and the normal state resistivity
- 1981
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 24:1, s. 144-154
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Tidskriftsartikel (refereegranskat)abstract
- Accurate measurements of the electrical resistance as a function of temperature and pressure are reported for Sn, Zr, dhcp La, and V. These measurements cover a temperature region around room temperature and pressures up to 1.3 GPa. From these data, including also our previous measurements for Al and published results for Pb, the pressure dependence of d ρ / dT (the resistivity-temperature derivative) is obtained. This quantity is found to be a significant factor in the pressure dependence of the electron-phonon interaction parameter λ. For the nontransition metals the relative pressure dependence of d ρ / dT is much larger than the compressibility. Therefore the pressure dependence of the superconducting Tc is quantitatively well accounted for by the resistance data for these metals. For the transition metals the pressure dependence of d ρ / dT is relatively smaller and Tc(p) calculated from the resistance data is, at the best, only qualitatively correct. These differences are discussed. Estimates for the pressure dependence of the plasma frequency are obtained.
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| 19. |
- Ross, Russel George, et al.
(författare)
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Thermal conductivity of solids and liquids under pressure
- 1984
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Ingår i: Reports on progress in physics (Print). - : IOP Publishing. - 0034-4885 .- 1361-6633. ; 47:10, s. 1347-1402
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Forskningsöversikt (övrigt vetenskapligt/konstnärligt)abstract
- Thermal conductivity of solids and liquids under pressure is covered in this review. Experimental techniques are critically considered and compared, and an introduction to theory is provided. Results are presented and discussed for ionic crystals, normal molecular crystals, plastic crystal phases, clathrate hydrates, polymers and glass-formers, liquids, covalent and semiconducting crystals, rocks and metals. Special attention is given to isochoric conditions, change of crystal structure and molecular orientational disorder. Available reliable measurements at pressures up to a few GPa indicate the need for theoretical development, especially in connection with molecular crystals and ferromagnetic metals.
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| 20. |
- Sandberg, Olov, et al.
(författare)
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Thermal properties of two low viscosity silicone oils as functions of temperature and pressure
- 1982
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Ingår i: Journal of Applied Physics. - : American Institute of Physics. - 0021-8979 .- 1089-7550. ; 53:12, s. 8751-8755
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Tidskriftsartikel (refereegranskat)abstract
- The thermal conductivity and the specific heat capacity per unit volume have been measured for two low viscosity grades of Dow Corning 200 fluid (polydimethyl siloxane) in the range 110 to 350 K and under pressures up to 2.0 GPa (20 kbar). Both the quantities studied are found to increase with increasing pressure in the liquid phase. From the measured data the phase diagrams are obtained. The 5 mm2/s (5 cSt) grade fluid does not crystallize, but undergoes a glass transition at 1.0 GPa at room temperature. The 1 mm2/s (1 cSt) grade has a more complicated phase diagram with a partly crystalline phase at low temperatures and pressures and two glass transitions at high temperatures and pressures.
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| 21. |
- Sundqvist, Bertil
(författare)
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C-axis resistance of stage 2 SbCl5 intercalated graphite under pressure
- 1988
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Ingår i: Synthetic Metals, volume 23. - : Elsevier B.V.. ; , s. 345-350
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Konferensbidrag (refereegranskat)abstract
- The c-axis resistance R of stage 2 SbCl5 intercalated graphite has been measured in the range 80–300 K and 0–4 GPa. The pressure dependence of R is similar to that of HOPG in the ordered low-T phase below 200 K but significantly larger at 300 K, where the initial pressure coefficient of R is −1.37 GPa−1. Two phase transitions are always observed under pressure, one at 0.3–0.5 GPa and one above 1 GPa. The latter is not completed until above 2.4 GPa and both are slow, with large time-dependent effects in R. R decreases by over 80% to 4 GPa.
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| 22. |
- Sundqvist, Bertil, et al.
(författare)
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Contactless basal plane resistivity measurements under pressure and the pressure/temperature phase diagram of stage 2 SbCl5 intercalated graphite
- 1986
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Ingår i: Journal of Physics C: Solid State Physics. - Bristol : Institute of Physics. - 0022-3719. ; 19:35, s. 6915-6929
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Tidskriftsartikel (refereegranskat)abstract
- The basal plane resistivity rho of stage 2 SbCl5 intercalated graphite has been measured as a function of temperature T and pressure p in the range 195-300K and 0-1.75 GPa, using a contactless method. rho is found to increase with increasing p. New evidence is found for the existence of the high-pressure (>1 GPa) phase suggested by Houser and co-workers (1984). The p/T phase boundaries for the low T(<230K) and intermediate p (>0.35 GPa) ordered phases are outlined. A re-analysis of previous results for stage 1 SbF5 intercalated graphite indicates a similar phase diagram for this material.
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| 23. |
- Sundqvist, Bertil, et al.
(författare)
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Contactless measurements of the basal plane resistivity of FeCl3 and SbF5 intercalated graphites under pressure
- 1984
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Ingår i: Journal of Physics C: Solid State Physics. - : IOP Publishing. - 0368-3516 .- 0022-3719. ; 17:5, s. L133-L138
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Tidskriftsartikel (refereegranskat)abstract
- The basal plane resistivities of stage 1 SbF5 and stage 2 FeCl3 graphite intercalation compounds have been measured for the first time at high pressure, using a recently developed contactless method. The resistivity is found to increase with increasing pressure in both materials. In the SbF5 intercalated material a phase transition was found at 1.2 GPa. This could be the first pressure-induced stage transformation observed in an acceptor intercalation compound.
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| 24. |
- Sundqvist, Bertil, et al.
(författare)
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Contactless methods for measuring electrical resistivity under pressure
- 1984
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Ingår i: High Pressure in Science and Technology, Part III: General Topics. - New York : North-Holland, Elsevier Science Publishing Co., Inc.. - 0444009310 - 0444009329 ; , s. 281-284
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Konferensbidrag (refereegranskat)abstract
- A new inductive contactless method to measure the electrical conductivity of metals under pressure is described. A ferromagnetic Metglas 2826 toroid core is used to minimize errors due to external magnetic fields. Experimental results for tin and brass are shown to agree very well with conventional four-terminal measurements.
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| 25. |
- Sundqvist, Bertil, et al.
(författare)
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Contactless resistivity measurements under high pressure
- 1983
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Ingår i: Journal of Physics E: Scientific Instruments. - Bristol : Institute of Physics. - 0022-3735. ; 16:5, s. 408-411
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Tidskriftsartikel (refereegranskat)abstract
- For the first time, a contactless inductive method has been devised for measurements of the electrical conductivity of metallic materials under very high pressures (>1 GPa). A sample in the form of a thin disc is placed in a pick-up coil in a steady-state AC magnetic field. The output voltage from the coil is analysed with a lock-in amplifier to find the component due to eddy currents in the sample, from which the conductivity is calculated, using a semi-empirical expression. The influence of the steel pressure vessel is eliminated by making simultaneous measurements on a known reference material. Experimental results are shown for tin and sodium up to 1.3 GPa.
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