Effect of iodine on properties of [GeS1.5]100 - xIx (x=0 ÷ 10) glasses

The [GeS1.5](100) - I-x(x) = 0 divided by 10) glasses are prepared by the reaction of germanium, sulfur and germanium (IV) iodide in vacuumed silica-glass ampoules at a temperature of 750-800 degrees C. Thermal, optical properties of glasses and their stability against crystallization are investigated. It is established, that, as the content of iodine in the matrix is increased from 0 to 10 at.%, the glass transition temperature value is decreased monotonically from 377 to 316 degrees C, and the short-wavelength transmission edge is shifted into the visible region from 811 to 605 nm. The stability against crystallization of the samples, estimated from the volume fraction of the crystalline phase after high-temperature annealing, raises with increasing iodine content. The investigated regularities of changes in the glass properties are interpreted within the framework of the glass net structure. As the most proper glasses in the Ge-S-I system for IR fiber optics, the [GeS1.5](90)I-10, [GeS1.5](92)I-8 and [GeS1.5](95)I-5 glass compositions are proposed.