Photoluminescent Zinc Sulfide Optical Ceramics

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New York State College of Ceramics at Alfred University. Kazuo Inamori School of Engineering.
Zinc sulfide is an attractive infrared (IR) optical ceramic material due to its desirable IR transmittance in the wavelength range of 8-12 μm. In this research, studies on the synthesis of ZnS powders and consolidation of ZnS ceramics were performed to understand the correlation between processing and property of ZnS optical ceramics. The photoluminescence characteristics of ZnS optical ceramics were also studied to provide rational discussions and interpretations of the phenomena. Four ZnS powders were synthesized via different wet chemical precipitation routes. Phase composition and microstructure analyses presented that they had pure cubic ZnS phases and finer particles with higher specific surface energy, compared with the commercial ZnS powders. In addition, it was found that the hot water bath route could contribute to slow and homogenous particle growth, resulting in synthesis of ZnS homogenous spherical particles. Second, the synthesized and commercial ZnS powders were consolidated by field assisted sintering technique (FAST) and vacuum hot pressing (VHP), respectively. It was revealed that the ZnS ceramics sintered by using the synthesized powders with homogenous particles had better densification and more desirable optical properties. Additionally, VHP was considered to be a more suitable sintering method to fabricate ZnS optical ceramics, due to the more sufficient densification and less carbon contamination. At last, the photoluminescence properties of the as-sintered undoped ZnS optical ceramics were measured. It was found that the blue emission was derived from the transfer of electrons from zinc vacancies to conduction band, and the green photoluminescence of the ZnS optical ceramics was due to the electron transfer in sulfur defects associated with elemental sulfur species. The increase of the green luminescence lifetime was attributed to processing conditions.
Advisory committee members: S.K. Sundaram, Dawei Liu. Dissertation completed in partial fulfillment of the requirements for the degree of Masters of Science in Ceramic Engineering at the Kazuo Inamori School of Engineering, New York State College of Ceramics at Alfred University