부산대학교 도서관

Density, viscosity and electrical conductivity of Na2O-GeO2 melts (0-50mol% Na2O) have been measured and the results have been interpreted assuming that the coordination change of Ge4+ from 4 to 6 occurs as Na2O is added to GeO2.The density-composition curve had a maximum at 7mol% Na2O. The partial molar volume (VGeO2) was derived from the molar volume by the intercept method, and the portion of Ge4+ ions in octahedral sites (N6) was estimated from VGeO2. The value of N6 increased linearly with increasing Na2O/GeO2 molar ratio, and had a maximum at 25mol% Na2O. On the other hand, N6 decreased with increasing Na2O/GeO2 ratio in the range from 25 to 40mol% Na2O. At 40mol% Na2O, there were no Ge4+ ions in octahedral sites.The dependences of viscosity, apparent activation energy for viscosity and equivalent conductivity on the composition could also be interpreted with the change of N6.