Date of Award
Master of Science (MS)
Materials Science and Engineering
Ellison , Michael S
Blouin , Vincent
Danto , Sylvain
Fargin , Evelyne
Chalcogenide glasses have been widely studied due to their extraordinary transparency in the infrared (IR) region from 0.5 to 20 μm. This transparency combined with excellent thermo-mechanical properties, makes them ideal candidate for infrared optics including IR fiber optic applications. However, such non-oxide glasses generally exhibit low mechanical strength, as compared to their oxide counterpart, which are based on covalently bonded metal-oxygen species. In addition to mechanical robustness, low optical loss (hence low impurity content) is required for most IR optical materials, including the one in this study, amorphous arsenic tri-selenide, As2Se3. In this effort, As2Se3 glass was investigated and the impact of the glass purity on material physical properties quantified. Properties evaluated includes chemical composition, structure, thermal, optical and mechanical properties.
There are many sources of optical loss in chalcogenide glasses, physical defects, heterogeneous phase(s), and oxide, hydroxide or hydride-containing species. These extrinsic impurities generally come from poor melting profiles, sample preparation or quality/purity of the raw materials. Reduction of intrinsic losses due of the material has also been explored. It was found that an impurity content of 0.1 ppb has to be reached to yield a total reduction of the band at 4.57 μm. Various methods, such as thermal treatment of the raw material or the addition of impurity-getters in the melt followed by distillation were performed in our lab, to achieve different level of purity in the glass specimens. The role of glass purity on these attributes was compared. The relationship between impurity concentration and mechanical properties of arsenic selenide glass, both in bulk and fiber forms has been investigated. The concentration of oxide-containing impurities embedded in the glassy matrix appeared to have a strong impact on the microhardness of the resulting material. A reduction of ~60% of the water, oxides and hydroxides content resulted in an increase of 200 MPa of the hardness of the glass system. Moreover, it has been demonstrated that the increase of the hydride (Se-H) content in the material would yield a lower microhardness of the glass. These observations have been correlated with the impact of the impurity concentration on the glass network connectivity. A material with weaker glass connectivity would exhibit smaller resistance to crack initiation. The evolution of the properties and homogeneity of the glass from small batch to preform and the effect of the drawing process have been studied. The results of the processing-related variables on final glass quality will be discussed.
Giroire, Baptiste, "Optimization of processing parameters for As2Se3 glass for low loss, high strength fibers" (2012). All Theses. 1413.