Hindered molecular reorientation of lithium ion doped succinonitrile in the terahertz range
The THz range permittivity of succinonitrile exhibits Debye-like behavior in its plastic-crystal phase, with a characteristic Cole-Cole relaxation time of 65ps ±17ps which increases considerably in the presence of ionic dopants.
Fast ion conduction in molecular plastic crystals
Doping of lithium salts and acids into the plastic crystal phase of succinonitrile has shown for the first time of the possibility of creating solid state electrolytes based on plastic crystalline solvents where the matrix itself is neutral and hence not intrinsically conductive. These materials illustrate the concept of a solid state electrolyte solvent. Room temperature conductivities up to 3.4×10−4 S cm−1 were obtained with 5 wt.% lithium bis(trifluoromethanesulfonylamide) in succinonitrile. Pulsed field gradient NMR measurements indicate that both cation and anion are mobile in this lattice. Proton conductivity was also observed when methane sulfonic acid or glacial acetic acid was used as dopants, however, the conductivity in these systems is limited by the poor dissociating ability of these acids.
Dielectric relaxation dynamics in C60 and C70
The electrical response of polycrystalline fullerites has been studied after annealing them under various conditions. Dielectric measurements have been carried out in the frequency range 100 Hz < ν < 1 MHz and for temperatures 10K < T < 300 K. For C60, electronic conduction, a phase transition and a dielectric relaxation process are clearly resolved. The latter is described by simple thermally activated behaviour but a broad spectrum of relaxation times, the origin of which is discussed. For C70, no clear experimental evidence for a similar dielectric relaxation process could be found in the temperature and frequency regime investigated.