Ž . Journal of Non-Crystalline Solids 209 1997 159–165 Density and microhardness of As–Se glasses and glass fibers C.T. Hach a, ) , K. Cerqua-Richardson b , J.R. Varner a , W.C. LaCourse a a NYS College of Ceramics at Alfred UniÕersity, Alfred, NY 14802, USA b UniÕersity of Central Florida, CREOL, Orlando, FL 32826, USA Received 8 August 1995; revised 31 May 1996 Abstract The density and Vickers microhardness of bulk glasses and glass fibers in the As–Se system have been determined for up to 50% As. Arsenic selenide glasses were batched in an argon atmosphere using high purity arsenic and selenium to produce samples that contained between 5 and 50% As, the balance being Se. The density and hardness of both fibers and bulk glasses increase up to the stoichiometric As Se composition, with the hardness exhibiting a maximum at this composition, 2 3 Ž² :. in accordance with the average coordination number r approach. The microhardness of aged fibers of all compositions is found to be higher than the corresponding bulk glass, indicating different structures. Both the density and microhardness of AsSe are found to increase rapidly with time after drawing. Density and microhardness results are discussed in terms of 4 quench induced stresses which result from the fiber drawing process, and stress relaxation in arsenic selenide glasses. 1. Introduction r overview Infrared-transmitting glasses based on sulfur, sele- Ž . nium, and tellurium i.e., chalcogenide glasses have w x been under investigation for nearly thirty years 1,2 . Presently these glasses are used to fabricate optical wx elements 1 , primarily lenses, and for use in infrared wx optical systems 1 . Because of their mid-IR trans- mission capability, chalcogenide glass fibers could wx eventually be used for laser-assisted surgery 1 . Many investigations of the optical and electrical w x properties of these glasses have been conducted 1,3 . However, the relative usefulness of a material for a particular application is mandated by its mechanical wx properties 1 . It is important to test materials in the ) Corresponding author. National Materials Advisory Board, National Research Council, 2101 Constitution Ave., Washington, DC 20418, USA. Tel.: q1-202 334 3510; e-mail: chach@nas.edu. form and shape they will have for a given applica- tion. In this study the density and hardness were Ž . examined for arsenic selenide As–Se glass fibers containing 5–50 mol% As, and comparisons were made with bulk samples. 1.1. Structure and bonding in As–Se glasses Pure vitreous Se consists of a mixture of Se 8 wx rings and long Se chains 2 . Intramolecular bond- n ing is covalent while only weak Van der Waals wx forces exist between rings andror chains 2 . When As is added, it polymerizes the structure by forming 3 bonds with Se, and acting as a cross-link between w x molecular units 2,8 . With continued addition of As, rings disappear with the formation of AsSe units 3 w x 2,8 . At the stoichiometric As Se composition Se– 2 3 Se bonds remain, and the structure is layered or sheet-like, composed of interconnected AsSe units 3 0022-3093r97r$17.00 Copyright q 1997 Elsevier Science B.V. All rights reserved. Ž . PII S0022-3093 96 00544-3