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There is now a CONTENT FREEZE for Mercury while we switch to a new platform. It began on Friday, March 10 at 6pm and will end on Wednesday, March 15 at noon. No new content can be created during this time, but all material in the system as of the beginning of the freeze will be migrated to the new platform, including users and groups. Functionally the new site is identical to the old one. webteam@gatech.edu
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MSE PhD Defense – Bryan Vitale
Date: Friday, October 16
Time: 3:30 pm
Location: Love Bldg, Rm. 295
Committee:
Dr. Robert F. Speyer, Adviser, MSE
Dr. Rosario A. Gerhardt, MSE
Dr. Joe K. Cochran, MSE
Dr. Thomas H. Sanders, MSE
Dr. Angus Wilkinson, Chemistry
Title: Synthesis of Higher Dense Ytterbium-Doped Lutetium and Undoped Yttrium Oxide for High Powered Lasing Application
Abstract: Utilizing transparent polycrystalline ceramics as laser host media offers many advantages over more conventional single crystal counterparts; improvements in scalability, higher dopant concentrations, and lower cost is achievable through these materials, and equivalent lasing efficiency and transparency can also be obtained. Polycrystalline sesquioxide ceramics offer the advantage of high room temperature thermal conductivity, and Yb3+-doped Lu2O3 specifically demonstrates minimal effect of solid-solution based phonon scattering via introduction of the lasing dopant. Such a material is an ideal candidate for a highly doped high-power laser operation with minimal thermal degradation. Yb3+-doped Lu2O3 disks were prepared by pressureless sintering and hot isostatic pressing (HIPing) mixed powder compacts. By selecting optimized sintering soak temperatures/times, HIPed specimens of theoretical density and good transparency were obtained. Discolorations and dispersed defects were minimized using air annealing treatments at 1100°C between sintering and HIPing, and using the minimum sintering soak temperature needed to achieve a closed-porosity state. A Yb2O3 solubility limit of between 8 and 10 mol% was indicated. Effects of sintering environment and HIPing schedule are also discussed, while optimized processing parameters, infrared transmittance, and lasing efficiencies are described. Y2O3 ceramics with ZrO2-3Y additions were also similarly evaluated as possible ceramic materials to be produced in this fashion.
