Preparation and characterization of rapidly quenched glasses in the systems R₂O—WO₃ (R=Li, Na, K)

Abstract

In the systems R₂O-WO₃ (R=Li, Na, K), the glass-forming region was extended by use of the rapid quenching technique combining a thermal-image furnace with a twin roller. The infra-red spectra revealed that the Li₂WO₄ glass contains no condensed macro-anions but only discrete ions of Li⁺ and WO ²⁻₄ . The glass transition temperature (T _g) and the crystallization temperature (T _c) were determined.T _g is affected very slightly by the type of alkali cations, whereas it is decreased with increase in the alkali oxide content. More than oneT _g was observed in Li₂O-WO₃ glasses, which is due to the formation of metastable phases. The conductivity of glasses containing the same amount of alkali oxide (of different types) increased with decrease in the radius of the alkali cation. Electrochromism was observed in the glasses with R=Li, Na; the electric field required for colouration is lower than that in WO₃ films. The electro-colouration is due to H_xWO₃ formed in the glass matrix by the double injection of protons and electrons.