The effect of grain boundaries on scintillation in rare-earth doped transparent ceramics
Abstract/Contents
- Abstract
- The need for large-scale, low-cost, novel materials for the active component in nuclear detector systems has sparked an interest in optically transparent ceramic scintillators as an alternative to single crystals. Ceramics may be produced in large sizes and to near net shapes, using standard methods of ceramic forming and sintering. Additionally, bulk slabs of certain materials compositions that may not be accessible by single-crystal growth may be produced as ceramics. Although ceramic scintillators have been used in commercial CT scanners for some time now, in other applications, they have not reached the levels of performance that single-crystal scintillators have. Research into the properties of ceramic scintillators has been restricted to a small number of materials, processed under a limited number of conditions. Many studies on ceramic scintillators point to possible "defects at the boundaries" as a source of degraded scintillator performance and an origin of deep trapping, but the true effect of grain boundary defect states on scintillator performance has not been well-characterized. Additionally, the unique processing methods required to produce not only dense, but transparent ceramics had only been used on a handful of materials prior to 15 years ago, and limited work has been done on materials with non-cubic crystal structures. In order to address these two limitations, this dissertation focuses on the sintering and scintillation properties of ceramics of three model materials, Eu:Y2O3, Ce:Y3Al5O12 (Ce:YAG) and Eu:SrI2. Transparent ceramics of these materials were sintered, including non-cubic Eu:SrI2 for the first time by inducing grain texture in ceramics of the material. Eu:SrI2 ceramics were found to have as proportional a response as single crystals and a light yield of 25% of single crystals and 55% of Tl:NaI. Through parametric studies of ceramic processing parameters, grain size, and bulk scintillation, the effect of grain boundaries on scintillator performance was compared to that from other sources of charge carrier trapping and light yield degradation. Using models for charge carrier generation and transport in a ceramic and a new micro-scintillation technique, X-ray radioluminescence microscopy, the localized effect of grain boundaries on scintillation was also characterized. Based on these micro-scale studies, a greater understanding of the effect of grain boundaries on bulk scintillation was developed. Based on the conclusions of these sintering and scintillation studies, a number of criteria are suggested for identifying new and existing scintillator materials that may be of interest for further investigation as ceramics, because of their potential to maintain high levels of scintillator performance and optical transparency when fabricated in ceramic form.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2011 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Podowitz, Stephen R |
|---|---|
| Associated with | Stanford University, Department of Materials Science and Engineering |
| Primary advisor | Cui, Yi, 1976- |
| Primary advisor | Feigelson, Robert S, 1935- |
| Thesis advisor | Cui, Yi, 1976- |
| Thesis advisor | Feigelson, Robert S, 1935- |
| Thesis advisor | McIntyre, Paul Cameron |
| Advisor | McIntyre, Paul Cameron |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Stephen Podowitz. |
|---|---|
| Note | Submitted to the Department of Materials Science and Engineering. |
| Thesis | Ph.D. Stanford University 2011 |
| Location | electronic resource |
Access conditions
- Copyright
- © 2011 by Stephen R. Podowitz
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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