GOALI: Addressing Persistent Oxygen in Sulfide-based, Longwave IR Transparent Ceramics

Infrared technology is used in applications like night vision, environmental monitoring, and space exploration and depends on materials that transmit infrared energy. This Grant Opportunity for Academic Liaison with Industry (GOALI) award focuses on improving a material called calcium lanthanum sulfide, which has the potential to outperform commonly used materials in harsh environments due to its strength, durability, and ability to transmit a wide range of infrared light. However, the key challenge that limits the performance of calcium lanthanum sulfide is small amounts of oxygen trapped inside the material during manufacturing. The unwanted oxygen severely reduces the transparency of this material at infrared wavelengths. This award is expected to develop advanced manufacturing processes that will eliminate the oxygen contamination in calcium lanthanum sulfide ceramics and produce a much clearer, high-performance infrared material. This advancement will enable better optical components for use in demanding environments, ultimately improving technologies that rely on infrared sensing and imaging. Research to be enabled by this award addresses the problem of persistent, dissolved oxygen in calcium lanthanum sulfide ceramics. The persistent oxygen severely degrades the optical transmission of the ceramic and is detected first in the incoming calcium lanthanum sulfide powder. Thus, two hypothesis driven tasks are investigated – one at the pre-sintering step and the second at the post-sintering step. First, to test the hypothesis that an external ‘oxygen gettering agent’ can be effectively used to extract oxygen from the raw powder, precise amounts of sub-stoichiometric metal oxides will be either premixed in nanopowder form or coated with atomic scale precision onto the raw sulfide powder. The choice of metal oxides will be such that its affinity for oxygen is greater than that of calcium lanthanum sulfide while the amounts are miniscule to not impact optical transmission. Second, to test the hypothesis that high temperature sulfur-rich environments can drive reactions where the sulfur can substitutionally replace oxygen, gas phase heat-treatment processes will be conducted on sintered ceramics, and the kinetics of the oxygen removal will be studied under various sulfur partial pressure conditions. Rate limiting steps and defect-based reactions will be identified and their impact on optical transparency understood. This award is expected to advance new, manufacturing-scalable processes that can eliminate persistent oxygen from calcium lanthanum sulfide ceramic and result in a transparent ceramic in the mid-to-longwave infrared spectral regime. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria. NSF Award ID: 2516156 | Program: 01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Parag Banerjee | Institution: The University of Central Florida Board of Trustees, ORLANDO, FL | Award Amount: $450,000 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2516156 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2516156.html