Optical, Structural, and Electrical Properties of TeO2 – Na2O – NaX Glasses (X = Cl, Br, I): Roles of Crucible Materials and Halides

Alkali tellurite glasses, which offer a broad glass-forming region along with large halide solubility, are excellent candidates as transparent conductive materials. TeO2 – Na2O – NaX (X = Cl, Br, I) glasses with halogen contents X ranging from 0 to 6 at. % (in total at. % of constituting elements Te, Na, O, and X) are investigated. Au crucibles alter their optical properties through the formation of inhomogeneously distributed gold nanoparticles. In contrast, alumina crucibles, despite undergoing a more severe dissolution, result in minor changes of the glasses’ structural and electrical properties. The electrical conductivity of such mixed anion glasses hinges on the mobility of the charge carriers (Na+ ions), and thus (i) on the bond strength of the Na-X bonds involved, as well as (ii) on the free volume within the glass network and consequently on the size of the anions. Accordingly, the electrical conductivity is found independent on the substitution rate for small halogens (X = Cl, Br), but increases up to threefold for large halogens (X = I).