Seminar: "Transparent Nd:YAG Ceramics", Dr. Adam Stevenson CREOL 102 Thursday, August 19, 2010 / 11:00am - 12:00pm
Adam Stevenson
Department of Materials Science and Engineering The Pennsylvania State University
Abstract:
Nd:YAG transparent ceramics have the potential to replace Czochralski grown single crystals in high power laser applications. However, after more than 20 years of development, there has been only limited application of these potentially revolutionary materials. In order to improve the processing and properties of Nd:YAG transparent ceramics and facilitate increased adoption, this presentation explores the effects of sintering aids on defects, densification and single crystal conversion
(SCC) of Nd:YAG ceramics. To explore the role of SiO2 doping in densification and microstructure development of Nd:YAG transparent ceramics,29Si magic-angle spinning nuclear magnetic resonance, high resolution transmission electron microscopy and sintering kinetics are used to show that SiO2 enhances densification and grain growth through a solid state mechanism. SiO2 content is shown to affect sintering trajectory and, therefore, the average grain size of highly transparent Nd:YAG ceramics can be controlled (2.8 μm - 18 μm) in highly transparent ceramics. Optical absorption spectroscopy and electron spin resonance are used to study the effects of SiO2 doping on color center formation in Nd:YAG transparent ceramics. F-centers are shown to be the primary color centers present after sintering and their concentration is controlled by impurity ions rather than SiO2 content. Finally, exaggerated grain growth in highly SiO2 doped 1 at% Nd:YAG ceramics is used to grow highly transparent Nd:YAG single crystals at 1600oC by the single crystal conversion process.
Biography:
Adam J. Stevenson received a BS in Materials Science and Engineering from the University of Illinois at Urbana-Champaign in 2003. After graduation, he joined Technology Assessment and Transfer, Inc. in Annapolis, MD as a Materials Engineer where his duties included developing green forming and sintering processes for transparent ceramic
MgAl2O4 hemispherical domes. In January 2005, Adam began graduate studies at The Pennsylvania State University under Professor Gary L.
Messing and will graduate with a Ph.D. in Materials Science and Engineering in December 2010. At Penn State, Adam’s studies focused on the effects of sintering aids on processing and properties of transparent Nd:YAG ceramics. Adam’s academic honors include the Arthur L. Friedberg Award for Academic Excellence, Leadership, and Involvement in Student Activities, the Arnulf I. Muan Fellowship in the College of Earth and Mineral Sciences, and the Graduate Student Award for Academic Excellence in Materials Science and Engineering. In September 2010, Adam will join Ecole National Superieur de Chimie de Paris as a post-doctoral scholar and researcher where he will develop processing and sintering methods for transparent Yb:CaF2 laser ceramics.
For More Information:
Martin C. Richardson
407-823-6819
No comments:
Post a Comment