Satoru Fujitsu

Enhancement of ionic conduction in CaF2 and BaF2 by dispersion of Al2O3

Ionic conductivity measurements were performed on polycrystalline CaF2, BaF2 and those dispersed with Al2O3 particles. The ionic conductivity of both CaF2 and BaF2 increased by about 1 to 2 orders of magnitude by dispersion of Al2O3 particles, while X-ray diffraction measurements showed there were no other phases present other than fluoride and Al2O3. The conductivity of the dispersed system strongly depended on the particle size and the concentration of Al2O3, which suggested the high ionic-conductivity layers were formed at the interface between the ionic conductor matrix and the Al2O3 particles. The effective thickness and electrical conductivity of the interface layer at 500° C were calculated, using a simple mixing model, to be 0.3 to ~ 0.6μm and ~ 10−3 S cm−1, respectively.

Formation of energy barrier by adsorbed on ZnO

Abstract The energy barrier on the surface of porous ZnO was formed by the chemisorbed oxygen. The height of such a barrier and the resultant change in the electrical conductivity depended on the amount and oxidation state of the adsorbed oxygen. The formed barrier was examined by measuring both current-voltage and capacitance-voltage characteristics. The barrier height decreased rapidly at room temperature, which was attributed to the change in the oxidation state of the chemisorbed oxygen. The addition of cobalt oxide stabilized the oxidation state of chemisorbed oxygen and increased the barrier height.

Enhancement of ionic conductivity of SrCl2 by Al2O3 dispersion

Abstract Enhancement of ionic conductivity was found in the system of SrCl2 and Al2O3 mixture. The enhancement of Cl- conductivity depended on the composition and the grain size of Al2O3. From these results, it was considered that the interface between SrCl2 matrix and Al2O3 particles played a role in giving rize to high ionic conductivity. The effective thickness and the conductivity of the interface layer were estimated by using a simple mixture model. The validity of this estimation was supported by the results of measurement for a modeled sample.

Gas-sensitive Ag ion conduction in semiconducting ZnO thin films

Abstract A new type of reducing gas sensing system has been developed based on changes in ionic conductivity. Though it is well known that the resistivity of n-type semiconductors such as ZnO decreases on the introduction of reducing gases, that of thin films sputtered on silica glasses in the present study (which had Ag electrodes) increased with the introduction of reducing gases. This abnormal property is due to the change in the ionic resistance of Ag+ incorporated from the electrode.