Structural Role of Zinc Oxide in Glasses in the System Na 2 O‐ZnO‐SiO 2

Glasses containing 50 to 75 mol% SiO 2 and up to 35 mol% ZnO were studied using thermal expansion, density, molar volume, refractive index, molar refractivity, internal friction, and infrared absorption data. Increasing the zinc oxide content in the glasses decreased the thermal expansion and increased the density, refractive index, and the activation energy for the alkali‐ion diffusion internal friction peak. Infrared absorption from 1500 to 70 cm ‐1 indicated the presence of both six and four oxygen coordination for the zinc cation.