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Ageing behaviors of the positive electrode of lithium ion battery are characterized by measuring mechanical properties of the electrode reeds, such as resonance frequency and internal friction, as a function of temperature. In the measurements of the electrode reeds with a sandwich structure of active material film and current collector of Al foil, two thermally-activated relaxation processes can be observed on the polyvinylidene difluoride binder in the active material film. Namely, a surface-related relaxation at ~150 K and a relaxation corresponding to the β-phase transition at ~240 K in the polymer binder can be observed at high signal/noise ratio. The resonance frequency decreases and the internal friction increases after charge/discharge cycling. The changes in activation energies of the relaxation processes also indicate that the measurement of mechanical properties of the positive electrode is an effective method for characterizing ageing behaviors of the positive electrode as a whole.

The electrical properties of microcrystalline Sc3N@C80 fullerene with fcc structure are studied by measuring both d.c. conductivity temperature dependence and a.c. impedance. Below 450 K the Sc3N@C80 sample has an energy band gap of 1.71 eV, which does not depend on the strength of the applied electric field. But when the temperature is above 450 K, a phase transition which results in a small band gap of 1.22 eV occurs under electric field strengths larger than 1 kV/cm. We also found from Cole–Cole plots of a.c. impedance that the contact resistance at the Au/Sc3N@C80 interface is less than that at the Au/C60 interface.

The current-voltage characteristics of the C70 solid with hexagonal closed-packed structures were measured in the temperature range of 250–450 K. The current-voltage characteristics can be described as a temporary expedient by a cubic polynomial of the voltage, i = a v 3 + b v 2 + c v + d. Moreover, the Meyer-Neldel temperature of the C70 solid was confirmed to be 310 K, at which a linear relationship between the current and voltage was observed. Also, at temperatures below the Meyer-Neldel temperature, the current increases with increasing voltage. On the other hand, at temperatures above the Meyer-Neldel temperature a negative differential conductivity effect was observed at high voltage side. The negative differential conductivity was related to the electric field and temperature effects on the mobility of charge carrier, which involve two variations in the carrier concentration and the activation energy for carrier hopping transport.

The transport property of carriers passing through a nanocrystalline Lu3N@C80/Au interface has been studied by measuring impedance under various alternating voltages and DC biases. A depletion layer thicker than 110 µm is recognized in the Lu3N@C80/Au Schottky contact. Such a thick depletion layer indicates that the formation of space charge in the nanocrystalline Lu3N@C80 phase is difficult owing to an increase in LUMO energy, i.e., a decrease in the electron affinity of the Lu3N@C80 molecule. A high interfacial resistance is found to increase the transmission time of the carriers passing through the Lu3N@C80/Au Schottky contact. Such a high interfacial resistance may be ascribed to the low mobility of the carriers in the nanocrystalline Lu3N@C80 phase.

The impurity bands and corresponding ionization energies of nitrogen atoms in a 4H-SiC crystal with a concentration of 1×1019 cm-3 are measured by a nondestructive and noncontact traveling-wave method. When a SiC sample was placed near the surface of a surface acoustic wave device, its conductivity can be obtained by measuring the attenuation of the piezo-potential traveling-wave grazing along the surface of the sample. Temperature-dependent conductivities corresponding to a freeze-out process of free carriers excited from nitrogen atoms were observed, and the corresponding ionization energies of the nitrogen atoms were estimated by the Arrhenius plot method. The ionization energies in the impurity bands originating from splits of the doping atoms at cubic and hexagonal sites in the carbon sublattice are 72.89 and 47.89 meV, respectively, at room temperature. The ionization energies are in good agreement with the results reported in other theoretical and experimental studies. We also found that the skin depth of the traveling wave in the sample is below 1 mm and that the mobility of the carriers is strongly affected by both ionized dopants and charged surface defects in the depletion region near the surface of the sample. The effects of the sample and traveling wave such as the polarization effects of the crystal and the frequency effects of the traveling wave are discussed.

The ground and excited states of Sb atom in Si, 1s (A 1), 1s (T 2), 1s (E), and 2p0, were measured by using a traveling-wave method. The Sb-doped Si crystal with donor concentration of 2 × 1015 cm−3 was placed the distance of 5 μm above a piezoelectric crystal in the fringe field of a surface acoustic wave. The free electrons excited from the bound states of the Sb atom are drifted by the traveling-wave, and thus lose their energy as the Joule heat through lattice and ion scattering processes. A strong temperature-dependent energy loss of the traveling-wave can be observed at temperatures below 200 K. The values of the bound states of the Sb atom can be characterized by using the Arrhenius plot for thermal activation process of the electrons in the bound states. The measurements were carried out at two frequencies of the traveling-wave, 50 MHz and 200 MHz. At the frequency of 50 MHz, the dielectric properties of the Si crystal are governed by dopant polarization but by electronic polarization at 200 MHz. We found that measurement accuracy of the bound states depends mainly on the electron mobility and the dielectric constant of the Si crystal, which are sensitive to the frequency and strength of the traveling-wave as well as electronic polarization properties of the Si crystal.