For the precise in-field identification of dangerous radioisotopes, the desire for higher resolution, cheaper, and more rugged gamma-ray scintillator detectors has pushed the materials science community to investigate new compounds and processing techniques. One particular solution is Eu:BaCl2 transparent ceramics processed by the novel phase-change sintering technique. Typically, optical transparency in BaCl2 would be limited by birefringence scattering at grain boundaries due to mismatch in refractive index. Traditional ceramic processing routes would also predispose this volatile and hygroscopic material to the formation of defects, which interrupt the energy transfer in the scintillation process. Literature shows that these challenges have prevented halide gamma-ray scintillator ceramics, including Ce:LaBr3, Eu:SrI2, and Ce:Cs2LiYCl6, from reaching the performance of their single-crystalline counterparts. The sintering method explored in this thesis utilizes a polymorphic orthorhombic to cubic phase transition followed by plastic deformation. The experimental implementation of this method necessitated the design of a unique airtight hot-pressing device, capable of developing conditions for this phase conversion, and the synthesis of high purity powders. Systematic experiments on powder synthesis and on densification were carried out to demonstrate the feasibility of this approach and understand the conditions for phase-change sintering. These experiments, supported by characterizations including x-ray diffraction, electron microscopy, and thermal analysis, lead to the production of optically isotropic cubic barium chloride ceramic samples. Finally, the optical and scintillation properties of Eu:BaCl2 ceramic samples were investigated, revealing an energy resolution of 6% at 662 keV, an unprecedented value for a halide ceramic scintillator.
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Doctor of Philosophy (Ph.D.)
College of Engineering and Computer Science
Materials Science Engineering
Materials Science and Engineering
Length of Campus-only Access
Doctoral Dissertation (Open Access)
Shoulders, William, "Stress-induced Phase Change Sintering: A Novel Approach to the Fabrication of Barium Chloride Transparent Ceramic Scintillators" (2016). Electronic Theses and Dissertations. 5628.