Novel High Temperature and Radiation Resistant Infrared Glasses and Optical Fibers for Sensing in Advanced Small Modular Reactors

One binary and three series of ternary non-oxide pure sulfide glasses compositions were investigated with the goal of synthesizing new glasses that exhibit high glass transition (T_g) and crystallization (T_c) temperatures, infrared transparency, and reliable glass formability. The binary glass series consisted of Ges₂ and La₂S₃ and the three glass series in the x(nBaS + mLa2S3) + (1-2x)GeS2 ternary system have BaS:La₂S₃ modifier ratios of 1:1, 1:2, and 2:1 with . With these glasses, new insights were realized as to how ionic glasses form and how glass modifiers affect both structure and glass formability. All synthesized compositions were characterized by Infrared (IR) and Raman spectroscopies and differential thermal analysis (DTA) to better understand the fundamental structure, optical, and thermal characteristics of the glasses. After a range of these glasses were synthesized, optimal compositions were formed into glass disks and subjected to gamma irradiation. Glass disks were characterized both before and after irradiation by microscope imaging, measuring the refractive index, density, and UV-VIS-IR transmission spectra. The final total dose the samples were subjected to was ∼2.5 MGy. Ternary samples showed a less than 0.4% change in density and refractive index and minimal change in transmission window. The glasses also resisted cracking as seen in microscope images. Overall, many glass compositions were developed that possess operating temperatures above 500 °C, where conventional chalcogenide glasses such as As₂S₃ and have T_gs from ∼200-300 °C, and these glasses have a greater than Tc – Tg values larger than 100 °C and this shows that these glasses have good thermal stability of Tg such that they can be fabricated into optical fibers and as such can be considered candidates for high temperature infrared fiber optics. Initial fiber fabrication efforts showed that selected glasses could be drawn but larger samples would be needed for further development and optimization.