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  • 1
    Electronic Resource
    Electronic Resource
    Dipolar relaxations in solid (CF4)1−x(CClF3)x (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 3111-3118 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: (CF4)1−x(CClF3)x shows a eutectic phase diagram with a eutectic temperature TE =69 K and a eutectic concentration xE =0.54. In the mixed crystal regime x〈0.015, dielectric audio frequency spectroscopy revealed the dynamics of weakly coupled CClF3 molecules performing thermally activated reorientations. An analysis of the data was performed in terms of a relaxator model including a critical comparison of different distributions of relaxation times. The static susceptibilities of the mixed crystals suggested a two-phase model of CF4, where rigid latice domains coexist with paraelastic regions. Several pure CClF3 samples were investigated using different thermal treatments. The dielectric dispersion of this compound is described by the reverse Havriliak–Negami expression and possible explanations for the origin of the relaxation spectra are discussed. The behavior of the CClF3 rich mixed crystals is considered briefly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456933
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  • 2
    Electronic Resource
    Electronic Resource
    Deuteron and carbon magnetic resonance studies of supercooled liquid and glassy salol (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 5884-5892 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The glass-former salol was studied using carbon and deuteron NMR. For the 13C measurements protonated samples were used. For the deuteron experiments salol was selectively deuterated at the phenyl ring. The measurement of the spin-lattice relaxation times provides clear evidence for an anisotropic reorientation of the molecules in the supercooled liquid. Close to the glass transition a bimodal longitudinal magnetization recovery is observed which indicates the presence of relatively slow intramolecular degrees of freedom. From deuteron solid echo spectra this process is identified as a uniaxial large amplitude motion of the phenyl group which exhibits a broad distribution of correlation times. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481161
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  • 3
    Electronic Resource
    Electronic Resource
    Decay of single and double quantum coherences in deuterated glassy ortho-terphenyl (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 8550-8556 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The decay of single and double quantum coherences in amorphous ortho-terphenyl is studied by means of deuteron NMR echo experiments near and below the calorimetric glass transition temperature Tg. In perdeuterated samples a Gaussian decay for these coherences is found at low temperatures, in accord with theoretical predictions for random local dipolar fields. A method is proposed to extract information about slow motional processes from ordinary solid echo experiments below Tg. Partly deuterated ortho-terphenyl does not show a Gaussian decay. Simple model calculations show that this observation indicates the importance of correlations of the local dipolar fields in the presence of protons. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476284
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  • 4
    Electronic Resource
    Electronic Resource
    Investigations of ferroelectric-to-paraelectric phase transition of vinylidenefluoride trifluoroethylene copolymer thin films by electromechanical interferometry (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 6367-6375 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electrostrictive and piezoelectric properties for a 1.3 μm thick film of a vinylidenefluoride/trifluoroethylene copolymer exhibiting a ferroelectric-to-paraelectric phase transition have been investigated as a function of temperature by means of electromechanical interferometry. The electrostriction remarkably increases in the vicinity of the phase transition temperature according to a sharp increase in the dielectric constant. For the unpoled sample in the ferroelectric phase with a polydomain structure in which the local spontaneous polarization is macroscopically cancelled out, the dependence of the electrostriction on the square of the applied electric field is nonlinear in the ferroelectric phase, while it is linear in the paraelectric phase. A theoretical model which takes into account the nonlinear dielectric constant can quantitatively explain the nonlinear contribution to the electrostriction in the vicinity of the ferroelectric–paraelectric phase transition, but it underestimates the contribution in the ferroelectric phase. Interactions within and/or between the ferroelectric domains in the polydomain structure are expected to contribute significantly to the nonlinear electrostriction. For poled samples a pronounced inverse-piezoelectric effect is measured. The achieved polarization and its temperature dependence are almost the same as for thicker films reported in earlier studies, obtained by different experimental techniques. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371699
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