Masanobu Kusakabe

The transport properties of cations in the superionic phase of AgxCu1-xI

Total electrical conductivities and transference numbers of the Ag x Cu 1- x I in α-phase have been measured as a function of temperature and composition. In this phase, it has been recognized that both Ag + and Cu + could be mobile accompanying with that the activation energies for both mobile ions are nearly the same and the transference number of both ions deviate from ideal values. This result indicates that the both mobile ions have the same conducting path although the amplitudes of their anharmonic thermal vibrations are different.

Ionic conductivity in silver-dissolved α-CuI

The electrical conductivity and the transference number of silver-dissolved α-CuI in the superionic phase were measured as a function of temperature and composition. It was recognized that both Ag and Cu ions could be mobile and the activation energy for Ag ions is smaller than that for Cu ions. It is emphasized that the size of the Ag ion is more suitable for conduction than that of the Cu ion in this phase. Since the ionic radius for the Ag ion is larger than that of the Cu ion, we propose a model other than the gate model to explain this experimental fact.

The transport properties of AgI-AgBr system in its superionic phase

Abstract Electrical conductivities and thermoelectric powers have been measured as a function of temperature and composition in AgI–AgBr system. The electronic conductivities in its superionic phase are negligibly small in comparison with ionic conductivities. The composition dependence of activation energies slightly decreases with increasing the bromine concentration. The lattice constant in this phase decreases with increasing the bromine concentration. The reduction of bottle neck size in conducting path of mobile ion, which originated from the decreasing of the lattice constant, produces the enhancement of activation energy. But this prediction is contradicted with the present observations. These behaviors may be attributable to a distortion of crystal lattice. The heat of transport obtained from measurements of thermoelectric power is slightly larger than the activation energy of ionic conduction in the superionic phase. This relation may be qualitatively explained by the model of Fokker–Plank equation.

The specific heat of the solid electrolyte system CuI-AgI

The specific heat for AgI-doped CuI has been measured by the method of differential scanning calorimetry. Anomalous specific heats were observed around the transition temperature from non-superionic to superionic phases. These were well explained in terms of the Schottky-type excess specific heat.

Ionic conductivity in copper-dissolved α-AgI

Abstract Total electrical conductivities and transference numbers of the Ag x Cu 1− x in the α-phase were measured as a function of temperature and composition. In this phase, it has been recognized that both Ag and Cu ions could be mobile and, in addition, the activation energies for both mobile ions are nearly the same. A structure refinement for this phase shows that both Ag and Cu ions vibrate at the 12d site with a large anharmonicity. However, the lattice constant obeys Vegards law. This result indicates that both mobile ions have the same conducting path although their amplitudes of anharmonic thermal vibrations are different.

Crystal structure of Ag+ doped α-CuI system

Powder X-ray diffraction measurements for Ag + doped α-CuI system in its superionic phase have been carried out. The most probable crystal structure seems to be an anti-fluorite one in which a part of cations are occupied at octahedral sites. The occupation probability of cation at the octahedral site rapidly increases with increasing Ag ion concentration. This result is qualitatively consistent with that obtained from the ionic conductivity measurements.Powder X-ray diffraction measurements for Ag + doped α-CuI system in its superionic phase have been carried out. The most probable crystal structure seems to be an anti-fluorite one in which a part of cations are occupied at octahedral sites. The occupation probability of cation at the octahedral site rapidly increases with increasing Ag ion concentration. This result is qualitatively consistent with that obtained from the ionic conductivity measurements.

Ionic conduction in dilute pseudo-binary systems CuBr-Cu2Se

Abstract Ionic conductivity, σ i , of dilute pseudobinary alloys (CuBr) 1−x (Cu 2 Se) x ( x ≤0.1) in their γ-phase has been measured by an ac method. The increase of the ionic conductivity propertional to x has been observed, which is attributed to interstitial ions brought by Cu 2 Se dissolved in CuBr. It is found that the temperature dependence of mobility of interstitial ions, μ , evaluated by the relation Δ σ i / x = kμ ( k is a constant) is bent at the temperature corresponding to the extrinsic–intrinsic transition of the based material CuBr.

Separation of the partial structure factors in molten copper halides and derivation of dielectric constants

Abstract The partial structure factors of molten copper haildes (CuCl, CuBr and CuI) have been derived from the observed total structure factors by means of the Reverse Monte Carlo simulation technique. The static dielectric functions are also obtained using these partial structure factors and it is found that these experimental dielectric functions satisfy either the inequality form e(q)e1 or e(q) < 0.

A theoretical extension for the electrical conductivity of molten salts

A microscopic description for the partial DC conductivities in molten salts developed by the present authors is briefly summarised, starting from the Langevin equation for the constituent ions. It is clarified that the memory function should be written as the form of , in which is the Fourier–Laplace transform in the long wavelength limit and the integration from zero to infinity for being unity. To solve the mutual relation between the combined velocity correlation functions to elucidate the DC conductivities and the memory function of the Langevin equation in a short time region, we propose a new recursion method. Practical application is carried out for the derivation of the fitted memory function from the of molten NaCl obtained by MD simulation. This fitted function in the short time region is approximated to a summation of three kinds of the Gaussian functions, and their physical interpretations are discussed.

Interfacial effect on electronic conductivities in amorphous selenium system

Abstract The electronic properties of p-type amorphous Se with dispersed n-type In 2 Se 3 crystals have been investigated to clarify the influence of the crystal size. In the present experiment, two kinds of samples were prepared by the rapid quenching method. One consists of nanocrystals embedded in an amorphous Se matrix, and the other is amorphous Se with dispersed microcrystals with an average diameter of 1.6 μm. A large change of the electronic conductivity with small additions of nanocrystal In 2 Se 3 was observed, while the conductivity for samples containing dispersed micron-sized crystals of In 2 Se 3 changes linearly with changing concentration. The difference is due to an interfacial effect.