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46. Thermal conductivity and thermopower studies of graphite intercalation compounds
130
Abstracts
curves is due to the simultaneous decrease in the number of carriers and increase in the space available for delocalisation. Standard conductivity theory (suitably modified to take dimensionality into account) is used and the charge transfer deduced. Agreement with available experimental data is quite satisfactory. 46. Thermal conductivity and thermopower studies of graphite intercalationcompounds B. Poulaert, J. Heremans, J. P. Issi, I. Zabala (Laboratoire de Physico-Chimie et de Physique de 1’Etat Solide UniversitCCatholique de Louvain, B-1348 Louvain-la-Neuve, Belgium) and H. Mazurek and M. S. Dresselhaus (Center for Materials Science and Engineering, M.Z.T., Cambridge, MA 02139). The temperature variation of the in-plane thermal conductivities in the range 2 < T < 300K are reported for stages 2, 3 and 6 FeC& and a stage-5 potassium graphite intercalation compounds. Thermopower data are also presented for the FeCls compounds. 47. Pressure-dependentresfstivftyof graphiteintercalation compounds C. D. Fuerst, D. Moses and J. Fischer (Laboratory for Research on the Structure of Matter, University of Pennsylvania, Philadelphia, PA 19104). We have measured the C-axis resistance of HOPG and several graphite compounds (KC*, K&) versus hydrostatic pressure up to 25 kbar. The results are interpreted in terms of variable interlayer overlap, interlayer charge screening and staging phase transitions. 48. Contactless magnetoresistance measurements with a rotatfngsample magnetometer P. J. Flanders and J. E. Fischer (Laboratory for Research on the Structure of Matter, University of Pennsylvania, Philadelphia, PA 19104). An anisotropic conductor rotating in a d.c. magnetic field exhibits induced eddy currents which can be detected by an external coil. The coil signal and its harmonics can be analytically related to the resistivity and the magnetoresistance. We show that for HOPG Ap,/p, vs T agrees with published data, and we apply the method to several acceptor compounds. 49. Quenching effects on the resfstfvity of some acceptor compounds P. Flanders, M. J. Moran, J. E. Fischer, (Laboratory for Research on the Structure of Matter, University of Pennsylvania, Philadelphia, PA 19104) and D. Billaud, G. Furdin, H. Fuzellier and A. Metrot (Laboratoire de Chimie du Solide Mineral, Universite de Nancy Z, 54037 Nancy, France). Using the rotating sample magnetometer, we have investigated the effect of cooling rate from 300 to 80K on p,(T). Rapid cooling (-20 set) produces as much as 30% excess low-T resistivity in compounds containing H or F (HN03, HzS04, N02SbF6, AsF5, HSOJF) but not others (SOS, Br2, ICI, alkali metals). We suggest the quenching in of disorder of Hor F-bonded intercalant layers.
50. Conductivity and optkal studies of fluorinated AsFsgraphite J. Milliken and J. E. Fischer (Department of Electrical Engineering, University of Pennsylvania, Philadelphia, PA 19104), and M. J. Moran and R. DeMarco (Naval Research Laboratory, Washington, DC). (Abstract not submitted). and ‘Li NMR studies of alkali-graphite inter51. ?s calation compounds G. Roth and K. Luders (Znstitutfiir Atom-und Festkiirperphysik, Freie UniversitiitBerlin, D- loo0 Berlin 33, Germany) and P. Pfluger and H. J. Giintherodt (Znstitut fiir Physik, Universitiit Basel, CH-4056 Basel, Switzerland). ‘33Cs and ‘Li NMR measurements on intercalated C&s and C,Li samples of HOPG and C&s powder samples are reported. The isotropic and axial part of the Knight shift K and the electric field gradient have been determined. K is considerably lowered compared to Cs and Li metal, respectively. For C&s this is mainly due to a reduction of N(&) whereas for C6Li charge transfer is also important. 52. “C NMR of KC&& A “benzene-potassium complex ion” graphite intercalationcompound F. Beguin and R. Setton (C.R.S.O.C.Z., C.N.R.S., lB, rue de la Ferollerie, 45045 Orleans, Cedex, France), L. Facchini, M. F. Quinton and A. P. Legrand (Laboratoire de Physique Quantique, ERA 676, ESPCZ, 10, rue Vauquelin, 75231 Paris, Cedex 05, France) and G. Hermann, (Briiker Spectrospin, 67160 Wissembourg, France). K&.+(Bz)~is studied by high field 13CNMR as compared to pure graphite, S, = 22 ppm for the graphitic planes; this is interpreted as a modification of the Knight shift due to changes in the conductivity of the planes. For the intercalated benzene, SII= 130ppm (in the plane) when referred to pure benzene at 220K; this value is interpreted as due to an increase in the number of electrons in the r orbitals of benzene. IV.INTERCALATIONOFGRAPHITE: LA'lTICEPROPERTlES
53. Raman spectra, Young’s modulus and resistfvity measurementson intercalatedgraphite fibers P. Kwizera, M. S. Dresselhaus and G. Dresselhaus (M.Z.T., Center for Material Science and Engineering 13-3021, Cambridge, MA 02139). Raman spectra of high modulus graphite fibers, (GY 70 and UC 4104B), intercalated with K, Rb, Cs, AlCl, and FeCb are reported. X-Ray diffraction is used to characterize the fibers with respect to staging. The effect of intercalation on Young’s modulus and resistivity will also be reported. 54. The microstructureof intercalatedgraphite ffbers P. Kwizera, J. S. Perkins, C. R. Desper and M. S. Dresselhaus (M.Z.T., Center for Material Science and Engineering 13-3021, Cambridge, MA 02139). The microstructure of two graphite fibers, GY 70 a polyacrylonitrile (PAN) based fiber, and UC 4104B, a pitch based fiber, is studied. We use scanning and transmission elec-
Abstracts
curves is due to the simultaneous decrease in the number of carriers and increase in the space available for delocalisation. Standard conductivity theory (suitably modified to take dimensionality into account) is used and the charge transfer deduced. Agreement with available experimental data is quite satisfactory. 46. Thermal conductivity and thermopower studies of graphite intercalationcompounds B. Poulaert, J. Heremans, J. P. Issi, I. Zabala (Laboratoire de Physico-Chimie et de Physique de 1’Etat Solide UniversitCCatholique de Louvain, B-1348 Louvain-la-Neuve, Belgium) and H. Mazurek and M. S. Dresselhaus (Center for Materials Science and Engineering, M.Z.T., Cambridge, MA 02139). The temperature variation of the in-plane thermal conductivities in the range 2 < T < 300K are reported for stages 2, 3 and 6 FeC& and a stage-5 potassium graphite intercalation compounds. Thermopower data are also presented for the FeCls compounds. 47. Pressure-dependentresfstivftyof graphiteintercalation compounds C. D. Fuerst, D. Moses and J. Fischer (Laboratory for Research on the Structure of Matter, University of Pennsylvania, Philadelphia, PA 19104). We have measured the C-axis resistance of HOPG and several graphite compounds (KC*, K&) versus hydrostatic pressure up to 25 kbar. The results are interpreted in terms of variable interlayer overlap, interlayer charge screening and staging phase transitions. 48. Contactless magnetoresistance measurements with a rotatfngsample magnetometer P. J. Flanders and J. E. Fischer (Laboratory for Research on the Structure of Matter, University of Pennsylvania, Philadelphia, PA 19104). An anisotropic conductor rotating in a d.c. magnetic field exhibits induced eddy currents which can be detected by an external coil. The coil signal and its harmonics can be analytically related to the resistivity and the magnetoresistance. We show that for HOPG Ap,/p, vs T agrees with published data, and we apply the method to several acceptor compounds. 49. Quenching effects on the resfstfvity of some acceptor compounds P. Flanders, M. J. Moran, J. E. Fischer, (Laboratory for Research on the Structure of Matter, University of Pennsylvania, Philadelphia, PA 19104) and D. Billaud, G. Furdin, H. Fuzellier and A. Metrot (Laboratoire de Chimie du Solide Mineral, Universite de Nancy Z, 54037 Nancy, France). Using the rotating sample magnetometer, we have investigated the effect of cooling rate from 300 to 80K on p,(T). Rapid cooling (-20 set) produces as much as 30% excess low-T resistivity in compounds containing H or F (HN03, HzS04, N02SbF6, AsF5, HSOJF) but not others (SOS, Br2, ICI, alkali metals). We suggest the quenching in of disorder of Hor F-bonded intercalant layers.
50. Conductivity and optkal studies of fluorinated AsFsgraphite J. Milliken and J. E. Fischer (Department of Electrical Engineering, University of Pennsylvania, Philadelphia, PA 19104), and M. J. Moran and R. DeMarco (Naval Research Laboratory, Washington, DC). (Abstract not submitted). and ‘Li NMR studies of alkali-graphite inter51. ?s calation compounds G. Roth and K. Luders (Znstitutfiir Atom-und Festkiirperphysik, Freie UniversitiitBerlin, D- loo0 Berlin 33, Germany) and P. Pfluger and H. J. Giintherodt (Znstitut fiir Physik, Universitiit Basel, CH-4056 Basel, Switzerland). ‘33Cs and ‘Li NMR measurements on intercalated C&s and C,Li samples of HOPG and C&s powder samples are reported. The isotropic and axial part of the Knight shift K and the electric field gradient have been determined. K is considerably lowered compared to Cs and Li metal, respectively. For C&s this is mainly due to a reduction of N(&) whereas for C6Li charge transfer is also important. 52. “C NMR of KC&& A “benzene-potassium complex ion” graphite intercalationcompound F. Beguin and R. Setton (C.R.S.O.C.Z., C.N.R.S., lB, rue de la Ferollerie, 45045 Orleans, Cedex, France), L. Facchini, M. F. Quinton and A. P. Legrand (Laboratoire de Physique Quantique, ERA 676, ESPCZ, 10, rue Vauquelin, 75231 Paris, Cedex 05, France) and G. Hermann, (Briiker Spectrospin, 67160 Wissembourg, France). K&.+(Bz)~is studied by high field 13CNMR as compared to pure graphite, S, = 22 ppm for the graphitic planes; this is interpreted as a modification of the Knight shift due to changes in the conductivity of the planes. For the intercalated benzene, SII= 130ppm (in the plane) when referred to pure benzene at 220K; this value is interpreted as due to an increase in the number of electrons in the r orbitals of benzene. IV.INTERCALATIONOFGRAPHITE: LA'lTICEPROPERTlES
53. Raman spectra, Young’s modulus and resistfvity measurementson intercalatedgraphite fibers P. Kwizera, M. S. Dresselhaus and G. Dresselhaus (M.Z.T., Center for Material Science and Engineering 13-3021, Cambridge, MA 02139). Raman spectra of high modulus graphite fibers, (GY 70 and UC 4104B), intercalated with K, Rb, Cs, AlCl, and FeCb are reported. X-Ray diffraction is used to characterize the fibers with respect to staging. The effect of intercalation on Young’s modulus and resistivity will also be reported. 54. The microstructureof intercalatedgraphite ffbers P. Kwizera, J. S. Perkins, C. R. Desper and M. S. Dresselhaus (M.Z.T., Center for Material Science and Engineering 13-3021, Cambridge, MA 02139). The microstructure of two graphite fibers, GY 70 a polyacrylonitrile (PAN) based fiber, and UC 4104B, a pitch based fiber, is studied. We use scanning and transmission elec-