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.