W0213

The Structure of Ge-P-S Glasses: Results from Neutron Diffraction. J.C. M^cLaughlin^*, B.R. Cherry^*, J.W. Zwanziger^* and B.G. Aitken^**, ^*Department of Chemistry, Indiana University, Bloomington, Indiana 47405, ^**SP-FR-05, Corning, Inc., Corning, New York 14831

A series of Ge-P-S glasses with a constant Ge-P ratio (Ge_2.5-P_1.0-S_x where x = 5.0-8.0) were studied using neutron diffraction. These glasses are being studied as model systems for applications of more complex sulfide glasses in photonics. The desirable optical and mechanical properties of these glasses include good infrared transmittance in the 3-5 µ range and high softening point¹. The Ge-P-S composition diagram (Ref. 1 Fig. 10) shows that, at low sulfur content, the glasses exhibit high softening point (greater then 480 ⁰C) and the most extended infrared transmittance. With increasing sulfur content, the softening point decreases and the infrared transmittance changes steadily. We seek to explain this by examining the structure of the glasses using several techniques, the first of which is neutron diffraction. As a three component glass is characterized by six independent partial structure factors, a single diffraction measurement will only provide a few gross details about the structure in the glasses. The neutron diffraction data is most sensitive to the Ge-Ge, Ge-S, and Ge-P distances in these glasses. The data show the basic Ge-S connections and Ge-Ge correlations at 2.3 and 3.5 Å, respectively. In addition to these strong features, weaker correlations possibly due to Ge-S from bridging sulfur at ~3.0 Å, and surprisingly a possible Ge-P correlation at 2.55 Å. In order to gain additional structural information complementary to the neutron diffraction data, ³¹P NMR, X-ray diffraction and Reverse Monte Carlo techniques will also be applied to these glasses.

¹A. Ray Hilton, Charlie E. Jones and Maurice Brau, Infrared Physics, 1964, Vol. 4, pp. 213-221.