SYNTHESIS OF HIGHLY DENSE YTTERBIUM-DOPED LUTETIUM AND UNDOPED YTTRIUM OXIDE FOR HIGH POWERED LASING APPLICA- TIONS A Thesis Presented to The Academic Faculty By Bryan Vitale In Partial Fulfillment Of the Requirements for the Degree Doctor of Philosophy in Materials Science and Engineering Georgia Institute of Technology December 2015 Copyright © Bryan Vitale 2015 SYNTHESIS OF HIGHLY DENSE YTTERBIUM-DOPED LUTETIUM OXIDE AND ZIRCONIA-STABILIZED YTTRIUM OXIDE FOR HIGH POWERED LAS- ING APPLICATIONS Approved by: Dr. Robert F. Speyer, Adviser Dr. Thomas H. Sanders School of Materials Science and School of Materials Science and Engineering Engineering Georgia Institute of Technology Georgia Institute of Technology Dr. Rosario A. Gerhardt Dr. Angus Wilkinson School of Materials Science and School of Chemistry and Engineering Biochemistry Georgia Institute of Technology Georgia Institute of Technology Dr. Joe K. Cochran Date Approved: School of Materials Science and Engineering Georgia Institute of Technology October 16th, 2015 ACKNOWLEGDEMENTS I would like to thank my family and friends who have supported me during my stay at Georgia Tech. Without their support, this project would not have been possible to com- plete. I would first and foremost like to thank my advisor, Dr. Robert Speyer, whose sup- port and guidance allowed me to overcome many challenges during this work. I would also like to thank my brother and roommate, Adam Vitale, for his moral support and for allowing me to vocalize project ideas to him at any time. I would especially like to thank my parents, Stephen and Gail Vitale, who have always been highly supportive and emo- tionally nearby. I also express my great appreciation for the assistance of my lab partners Morris Satin and Joseph Eun as well as the various undergraduate research associates who contributed to the project in various ways for their numerous contributions and sug- gestions. Lastly, I thank the Air Force Office of Scientific Research, Contract FA9550- 12-1-0219, for funding the project work, and I appreciate the helpful suggestions and support of the contract monitor, Dr. Ali Sayir. iii TABLE OF CONTENTS ACKNOWLEGDEMENTS ............................................................................................... iii LIST OF TABLES ............................................................................................................ vii LIST OF FIGURES ......................................................................................................... viii SUMMARY ................................................................................................................... xviii I. INTRODUCTION ............................................................................................................1 II. LITERATURE REVIEW ................................................................................................7 2.1 Material Data .....................................................................................................7 2.1.1 Lutetium Oxide .........................................................................................7 2.1.2 Ytterbium Oxide .....................................................................................10 2.1.3 Yttrium Oxide .........................................................................................11 2.1.4 Zirconium Oxide .....................................................................................12 2.2 Laser Fundamentals .........................................................................................12 2.2.1 Rare Earth Spectroscopy .........................................................................21 3+ 2.2.2 Emission of the Yb ion .........................................................................23 2.3 Sintering and Ceramic Processing ...................................................................25 2.3.1 Pressing and Powder Consolidation........................................................26 2.3.2 Solid-State Sintering ...............................................................................34 2.3.3 Chemical Co-precipitation ......................................................................42 2.3.4 Ball Milling .............................................................................................45 2.3.5 Sonication and Sedimentation.................................................................48 2.3.6 Spray Drying ...........................................................................................52 2.3.7 Sintering of Traditional Nd:YAG Ceramics ...........................................54 2.4 Sintering of Sesquioxide Ceramics ..................................................................62 2.4.1 Hot Pressing of Y2O3 and Lu2O3 Ceramics ............................................65 2.4.2 Laser Synthesis of Y2O3 Ceramics .........................................................67 iv 2.4.3 Microwave and Combustion Reaction Sintering of Y2O3 Ceramics ................................................................................................70 2.4.4 Spark Plasma Sintering of Sesquioxide Ceramics ..................................75 2.4.5 Traditional Sintering of Sc2O3, Y2O3, and Lu2O3 ceramics ....................79 III. SINTERING OF AS RECEIVED COMMERCIAL POWDERS ...............................88 3.1 Experimental Procedures .................................................................................88 3.1.1 Consolidation and Sintering Procedure ..................................................88 3.1.2 Archemedes Density Measurements and Open/Closed Porosity ............89 3.1.3 Air Annealing and Polishing of Ceramic Samples .................................90 3.1.4 X-ray Diffraction Analysis Methodology ...............................................92 3.1.5 Optical and Spectroscopic Analysis........................................................93 3.2 Sintering Results ..............................................................................................95 3.3 X-ray Diffraction Results ...............................................................................104 3.4 Transmission and Emission Results...............................................................107 IV. SINTERING OF PROCESSED COMMERCIAL POWDERS ................................120 4.1 Experimental Procedures ...............................................................................122 4.1.1 Sintering of Co-precipitated Lu2O3 Powders ........................................123 4.1.2 Sonication and Sedimentation of Lu2O3 and Y2O3 Powders ................125 4.1.3 Sintering of Jet and Ball Milled Lu2O3 and Y2O3 Powders ..................127 4.1.4 Sintering of Spray Dried Lu2O3 and Y2O3 Powders .............................129 4.2 Sintering Results ............................................................................................132 4.2.1 Elevated Graphite Element Furnace Sintering Results .........................134 4.2.2 Processed Powder Graphite Element Sintering Results........................139 4.2.3 Processed Powder Tungsten Element Furnace Sintering Results .........170 4.2.4 Optimizing Plasticizer Content in Graphite/Tungsten Sintering Environments .......................................................................................176 4.2.5 Impurity Determination of Sintered Ceramics ......................................182 4.2.6 Achieving Near 100% Relative Density with Pure Lu2O3 Ceramics ..............................................................................................199 v V. CONCLUSIONS AND RECOMMENDATIONS .....................................................206 REFERENCES ................................................................................................................210 VITA ................................................................................................................................217 vi LIST OF TABLES Table 1: Transport mechanisms and the result of the microstructure of a ceramic during sintering[52, 54, 56]. ..................................................................................................34 Table 2: Comparison of microwave and vacuum sintering methods[81]. .............................71 Table 3: Comparison of fluorescence spectra between YAG[94], single crystal Yb:Lu2O3[95], and polycrystalline Yb:Lu2O3[51]. ................................................................86 Table 4: Initial sintering results of spray dried 5 mol% ZrO2-Y2O3. While samples were not of good quality, high sintered densities were identified with high dependence on sinter duration. ..............................................................................................166 vii LIST OF FIGURES Figure 1: Graphical representations of the bixbyite structure[29, 30]. ..................................8 Figure 2: The coordination of the two types of lutetium sites in Lu2O3[32]. ........................9 Figure 3: Simulated XRD pattern from micro-pulldown single crystal (bottom), experimental XRD pattern from grinded compound (top), and experimental XRD pattern from transparent ceramic (middle)[32]. .....................................................................10 Figure 4: Basic illustration of laser light emission[37]. .........................................................13 Figure 5: Two common energy level schemes for laser operation, the thick arrow illustrates stimulated emission, described below[37]. ...........................................................14