부산대학교 도서관

The electrical conductivity and dielectric relaxation of glasses in the system MnO-Fe2O3-P2O5 were studied over the temperature range 20-16°C. This system contains MnO and Fe2O3, both of them confer an electronic conduction. The samples used in the experiment were prepared under following conditions, i.e.1) melting in the air, being kept for about 2h at 350°C, and then gradually cooling (normally cooled glass), 2) melting with a reducing agent, being kept for about 2hrs. at 350°C, and then gradually cooling (reduced glass), 3) melting in the air and then annealing at a temperature above 100°C than Tg (annealing glass or crystallized glass).The ratio (Fe2+/Fe2++Fe3+) in the system was analyzed chemically and the effects of the ratio on the electrical properties were determined in connection with the composition of the glass. The conductivity in the (50-x)MnO-xFe2O3-50P2O5 glasses increased linearly by replacing MnO with Fe2O3. The conductivities of the reduced iron-containing glasses was about one order of magnitude higher than those of the normally cooled glasses. The conductivity of crystallized glass having composition 50MnO-50P2O5 was greater than about 5.5 order of magnitude over those of the normally cooled glass, and the straight line representing the relation between log σ and 1/T was found to break at about 80°C. These facts suggest that the preferential segregation of transition metal, consisting of a particular oxidation state, would be assumed to explain the large change in conductivity observed in this crystallized glass. The dielectric constant ε' and dielectric lossε'' increased with the increase of the amount of Fe2O3. In the reduced glass containing MnO and Fe2O3, the dielectric loss ε'' increased with the increase of the amount of Fe2+ion. The value of ε'' max decreased with increasing the annealing temperature.Relaxation losses in these glasses containing transition elements are considered to be related to the electron transition between the two different valences of the elements and the manner of distribution of the elements in the glass.