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A Study of Crystallization Behavior in Phase Separated Chalcogenide Glasses

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Date Issued:
2016
Abstract/Description:
Chalcogenide glasses (ChG) are known for their wide transmission ranges in the infrared and for their high refractive indices. However, applications for ChG are often limited by their poor thermal/mechanical properties. Precipitating a secondary crystalline phase in the glass matrix can improve these properties, but too much crystallization and/or large or multiple phase crystallites can lead to a loss in infrared (IR) transmission. Controlled crystallization can be used to tune the properties of these glasses. This work examines the crystallization behavior in phase separated chalcogenide glasses in the GeSe2-As2Se3-PbSe glass system.Specifically, the research presented in this thesis work has investigated the crystallization behavior in the 20GeSe2-60As2Se3-20PbSe (20 PbSe) and 15GeSe2-45As2Se3-40PbSe (40 PbSe) glasses for an IR optical system operating in the 3 to 5 (&)#181;m range. While both of these glasses were found to have droplet-matrix phase separation, the morphology differed from each other in two key ways. First, the droplets seen in the 20 PbSe glass (100-130 nm) are roughly twice as big as those in the 40 PbSe glass (35-45 nm). The droplet sizes seen in the base glass directly affect the short wavelength cutoff of the two glasses where the 20 PbSe glass (1.993 (&)#181;m) has a longer wavelength cutoff than the 40 PbSe (1.319 (&)#181;m). Secondly, the 20 PbSe glass has Pb-rich droplets and the 40 PbSe glass has a Pb-rich matrix, impacting where the initial stages of crystallization are initiated. Crystallization occurs in the Pb-rich phase and affects the glass-ceramic properties differently depending on whether the Pb-rich phase is the minority phase (20 PbSe) or the majority phase (40 PbSe). When the crystallization occurs in the majority phase, it greatly affects the hardness, density, and refractive index. When the crystallization occurs in the minority phase, the hardness and density change negligibly while the refractive index still shows significant change. While both glasses show an effective index change and 3-5 (&)#181;m transmission in their base form, only the 40 PbSe maintains the transmission window after the heat-treatments used in this study.The work reported in this thesis has shown how the crystallization process can be used to develop a gradient refractive index (GRIN) component in an IR optical system. While the composition and crystallization protocols are not optimized for further transfer of the technology to commercial products, the basis of this work shows the process of developing a glass-ceramic for the application.
Title: A Study of Crystallization Behavior in Phase Separated Chalcogenide Glasses.
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Name(s): Buff, Andrew, Author
Richardson, Kathleen, Committee Chair
Sohn, Yongho, Committee Member
Gaume, Romain, Committee Member
Fargin, Evelyne, Committee Member
University of Central Florida, Degree Grantor
Type of Resource: text
Date Issued: 2016
Publisher: University of Central Florida
Language(s): English
Abstract/Description: Chalcogenide glasses (ChG) are known for their wide transmission ranges in the infrared and for their high refractive indices. However, applications for ChG are often limited by their poor thermal/mechanical properties. Precipitating a secondary crystalline phase in the glass matrix can improve these properties, but too much crystallization and/or large or multiple phase crystallites can lead to a loss in infrared (IR) transmission. Controlled crystallization can be used to tune the properties of these glasses. This work examines the crystallization behavior in phase separated chalcogenide glasses in the GeSe2-As2Se3-PbSe glass system.Specifically, the research presented in this thesis work has investigated the crystallization behavior in the 20GeSe2-60As2Se3-20PbSe (20 PbSe) and 15GeSe2-45As2Se3-40PbSe (40 PbSe) glasses for an IR optical system operating in the 3 to 5 (&)#181;m range. While both of these glasses were found to have droplet-matrix phase separation, the morphology differed from each other in two key ways. First, the droplets seen in the 20 PbSe glass (100-130 nm) are roughly twice as big as those in the 40 PbSe glass (35-45 nm). The droplet sizes seen in the base glass directly affect the short wavelength cutoff of the two glasses where the 20 PbSe glass (1.993 (&)#181;m) has a longer wavelength cutoff than the 40 PbSe (1.319 (&)#181;m). Secondly, the 20 PbSe glass has Pb-rich droplets and the 40 PbSe glass has a Pb-rich matrix, impacting where the initial stages of crystallization are initiated. Crystallization occurs in the Pb-rich phase and affects the glass-ceramic properties differently depending on whether the Pb-rich phase is the minority phase (20 PbSe) or the majority phase (40 PbSe). When the crystallization occurs in the majority phase, it greatly affects the hardness, density, and refractive index. When the crystallization occurs in the minority phase, the hardness and density change negligibly while the refractive index still shows significant change. While both glasses show an effective index change and 3-5 (&)#181;m transmission in their base form, only the 40 PbSe maintains the transmission window after the heat-treatments used in this study.The work reported in this thesis has shown how the crystallization process can be used to develop a gradient refractive index (GRIN) component in an IR optical system. While the composition and crystallization protocols are not optimized for further transfer of the technology to commercial products, the basis of this work shows the process of developing a glass-ceramic for the application.
Identifier: CFE0006271 (IID), ucf:51032 (fedora)
Note(s): 2016-08-01
M.S.M.S.E.
Engineering and Computer Science, Materials Science Engineering
Masters
This record was generated from author submitted information.
Subject(s): Chalcogenide -- Glass -- Crystallization -- Glass-ceramic -- Phase Separation -- Nucleation -- Growth
Persistent Link to This Record: http://purl.flvc.org/ucf/fd/CFE0006271
Restrictions on Access: public 2016-08-15
Host Institution: UCF

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