Na₂O, MnOを含む燐酸塩ガラスの電気伝導と誘電緩和

抄録

The electrical conduction and dielectric relaxation of some glasses in the system Na₂O-MnO-P₂O₅ were studied over the temperature range 20°-180°C. This system contains Na₂O confering an ionic conductivity on glass and MnO confering an electronic conductivity.
In this study the electrical conductivity and dielectric properties were measured on both samples ordinarily cooled and properly heat treated. The results were discussed by considering the dependency of the composition, especially of the ratio MnO/P₂O₅, on the conductivity. In this series xNa₂O-(50-x)MnO-50P₂O₅ the conductivity decreased with increasing the ratio MnO/P₂O₅, i.e. with decreasing Na₂O content. In the non-alkali glass series xMnO-(100-x)P₂O₅ the conductivity showed to have a maximum value at the MnO/P₂O₅ ratio of about 0.67. The heat treatment was found to affect greatly on the conductivity. The linear relationship between log σ and 1/T was found in the glass containing a large amount of MnO, but the linear lines bent into two straight lines in the samples subjected to a proper heat treatment at a high temperature. The activation energy (ΔH_dc) of glasses of the formula xNa₂O-(50-x)MnO-50P₂O₅ was obtained by replacing MnO with Na₂O. The curve representing the relation between the activation energy and the composition was found to show a minium at the composition near x=25mol% and a maximum near x=30mol%.
The dielectric relaxation was observed by changing frequency and temperature. The frequency f_max at which the dielectric absorption shows a maximun was seen to shift toward a higher frequency with the increasing amount of Na₂O. The relationship between σ and the frequency at which the dielectric loss indicates a maximum, f_max, follows the equation proposed by H. Namikawa but in the heat treated glasses this equation does not hold.