부산대학교 도서관

The electrical conductivity (σ) and dielectric relaxation of glasses in the system Fe2O3-MnO-P2O5 were studied over the temperature range 20°-180°C. The glasses were prepared by melting under various conditions i.e., melting in the air and in a reducing atmosphere and by an annealing condition. The ratio (Fe3+/Fe3++Fe2+) in the system was analyzed by chemical method and the effects of the ratio on the electrical properties were also determined in connection with the composition of the glasses.In the measurement of d.c. conductivity (σ) on glasses in the system xFe2O3-(40-x) MnO-60P2O5, the values increased by replacing MnO with Fe2O3 as shown in Fig. 4. The activation energy ΔHdc of the glass 40MnO-60P2O5 was about twice that of the glass 40Fe2O3-60P2O5.In the glass containing MnO, the conductivity decreases with the amount of MnO. The glass reduced by carbon during melting was found to decrease the conductivity (Fig. 5). In the glass containing Fe2O3, the conductivity increased with increasing FeO, the ratio (Fe3+/Fetotal) and the total amount of iron content in some limit (Fig. 6). In the system Fe2O3-MnO-P2O5, however, the conductivity was found to be unaltered with the ratio (Fe3+/Fetotal) and by heat treatment (Fig. 8).It is suggested that in this system the multi-valency of manganese and iron may be affected with each other by oxidation and reduction, but its final state may practically be uneffected on the electronic conductivity. The conductivity in this system was observed to vary greatly with the glass composition.The dielectric relaxation was observed by changing frequency and temperature. The frequency fmax at which the dielectric absorption shows the maximum was seen to a higher frequency with the amount of Fe2O3 and with the measuring temperature. The relation between logarithmic values of the fmax and 1/T showed a straight line, from which the activation energy ΔHac was calculated (Eq. 5 and Fig. 8). From the correlation between d.c. conductivity and dielectric absorption, the following formula has been presented by T. Nakajima & H. Namikawa.σ≅ε0⋅Δε⋅2πfmaxThe relationship was determined to hold in the system Fe2O3-MnO-P2O5 as shown in Fig. 12.