Structure of Molten Oxides. I. Viscosity of GeO2, and Binary Germanates Containing Li2O, Na2O, K2O, and Rb2O

摘要

An improved counterbalanced sphere viscometer was used to determine the viscosity of pure molten GeO2at temperatures from 1470deg; to 1720deg;C. This data agrees with the Kurkjian and Douglas data obtained below 1500deg;C. Activation energy and entropy calculations suggest a gradual thermal breakdown of molten GeO2compared to SiO2.Viscosity information was obtained at temperatures between 1000deg; and 1500deg;C for binary alkali germanate melts containing up to 32 mole Li2O, Na2O, K2O, and Rb2O. Viscosity isotherms, activation energies, and activation entropies suggest gross similarities between the viscous flow mechanisms of binary alkali germanate and silicate melts. However, differences of detail imply divergent modes of network alteration with the addition of a given amount of alkali oxide.