Abstract
When the network-forming trivalent ions are introduced into the sodium silicate glasses, the network structure of glasses gives rise to the characteristic change in the binding state of oxygen. To elucidate the change, the electrical conductivity of 2Na2O⋅xR2O3⋅(8-x)SiO2 glasses (R: B, Al, Ga and La) has been measured in the wide temperature range from solid to molten states and the change of the binding state in oxygen with addition of a trivalent ion was analyzed through the shift of O1s peak by means of X-ray photoelectron spectroscopy, and the effects of the various trivalent ions on the conductivity were discussed with their structure. In the molten state (above Tg), the electrical conductivity of each system decreased with increasing content of various trivalent ions. Particularly for the network-forming ions such as B3+, Al3+ and Ga3+ ions, the conductivity decreased linearly with increasing [RO4]-Na+/∑Na+ ratio except Al/Na>1 and Ga/Na>1 and the values of conductivity coincided with each other in the same composition ratios. The results show that the network structure of each system retains the similarity of compositional influences on the mobility of Na+ ions, even though the different kinds of trivalent ions are introduced. In the solid state (below Tg), the conductivity did not simply depend upon the composition, but upon the glass structure in equilibrium with the frozen temperature (≅Tg) from melt to glass. The opposite behavior of B3+ ion and Al3+ ion of the conductivity in solid states can be explained by the difference of frozen temperatures. While the conductivity of the glass containing La3+ ion as the network-modifier decreased steeply with increasing content of the ion in both the solid and molten states. According to Anderson's model, it was assumed that the binding energy for Na+ ion in the activation energy increased in about 4-5kcal/mol with variation from 0 to 1 in R/Na.
