Investigation on the kinetics of devitrification of GeS 2 -based glasses
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We studied the devitrification kinetics for the binary (80GeS2–20Ga2S3, mol%) and ternary (77GeS2–15Ga2S3–6CsI, mol%) glass compositions using the differential thermal analysis (DTA) technique. The overall activation energies for devitrification for these two types of glasses were determined by using the Kissinger method and the Johnson–Mehl–Avrami equation from the DTA data. The t-t-t curves were calculated using the activation energy for devitrification for each composition derived from the DTA experiments. The experimental evidences have shown that the incorporation of SnS2 and Sb2S3 in a ternary-based GeS2 glass slows down the overall devitrification rate significantly, which is confirmed by the reduction in the overall area under the crystallization exotherm.
I. INTRODUCTION
Germanium sulphide (GeS2) is well known for its glass-forming ability.1–3 Bulk GeS2 glasses, depending upon their compositions, exhibit a wide transmission range spanning from 0.45 to 10 m. In the 1990s, the GeS2-based glasses were explored as a potential host for 1.3-m Pr-doped fiber amplifiers; however, only a limited success was achieved. It was reported that GeS2based chalcogenide glasses, which exhibit large solubility for rare-earth ions, are the most promising materials for Pr-based devices.4–6 The rare-earth ion doped chalcogenide glasses are also candidates for designing nearinfrared (NIR) and mid-infrared (mid-IR) lasers because of their low phonon energies (300–450 cm−1) and high refractive indices, which reduce the phonon-mediated rate and yield large emission cross-section respectively, thereby leading to potentially large gain devices. Some vibrational spectroscopic features of Pr3+doped GeS2-based glasses were studied in details in our earlier papers.4,7,8 It was reported that the chalcogenide glasses have large third-order nonlinearity between 20 and 70 times compared with silica at 1500 nm, and the glass fibers are promising for all-optical switching applications.9–11 To design fiber-based devices, characterization of thermal stability and devitrification characteristics of GeS2-based glasses are essential. Formation of crystals
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2005.0125 856
http://journals.cambridge.org
J. Mater. Res., Vol. 20, No. 4, Apr 2005 Downloaded: 15 Mar 2015
during reheating of glass preforms during fiber fabrication contributes to overall linear loss via light-scattering centers in optical fibers and therefore reduces the performance of fiber device. For this paper, the kinetics of devitrification of GeS2-based glasses was studied using a differential thermal analyzer (DTA) to determine the critical temperature range, in which the devitrification process becomes significant. The effect of glass compositions for minimizing the devitrification during reheating is also reported in conjunction with the kinetics of glassto-crystal transformation. The overall activation energy for devitrification was determined using the Kissinger method and the Johnson–
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