DOCSLIB.ORG

Microstructure and Defect Chemistry of Yttrium Aluminium Garnet Ceramics

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text

Load more

INIS-mf—12558 NL89C1183 MICROSTRUCTURE AND DEFECT CHEMISTRY OF YTTRIUM ALUMINIUM GARNET CERAMICS IV I I Hb | Ilia efc • j — log pO, c _ LOTHAR H. SCHUH r \* Cover: The Defect Diagram Of Ca-Doped YAG MICROSTRUCTURE AND DEFECT CHEMISTRY OF YTTRIUM ALUMINIUM GARNET CERAMICS »•#i-*» MICROSTRUCTURE AND DEFECT CHEMISTRY OF YTTRIUM ALUMINIUM GARNET CERAMICS PROEFSCHRIFT ter verkrijging van de graad van doctor aan de Technische Universiteit Eindhoven, op gezag van de rector magnificus, prof. ir. H. Tels, voor een commissie aangewezen door het college van dekanen in het openbaar te verdedigen op vrijdag 25 augustus 1909 te 16.00 uur. door LOTHAR HKRBSBT SCHUH geboren te Hermülhelm (West-Duitsland) Dlt proefachrlit la goadfakaurd door da proaotoren Prof. dr. R. Hataelaar •n Prof. dr. a. de With CONTENT 1 INTRODUCTION. i 2 THE GARNET STRUCTURE 4 3 LITERATURE REVIEW: OErECT PROPERTIES OF OARNETS 7 3. 1 IRON GARNETS 7 3. 1. l Oxygen diffusion in YIG 8 3. 1. 2. Cation diffusion In YIG 10 3. 1. 3 Direct determination of oxygen vacancies in YIG 12 3. 1. 4 Electrical conductivity and thermo-electric power in YIG 13 3. 1. 5 Other iron garnets 15 3. 2 YTTRIUM ALUMINIUM AND OTHER GARNETS 15 3. 2. 1 Oxygen diffusion in YAG 16 3. 2. 2 Electrical conductivity in YAG and other non iron garnets 17 3. 3 SITE EXCHANGE EFFECTS IN GARNETS 19 4 LITERATURE REVIEW: COLOUR CENTRES AND PARAMAG- NETIC DErECTS IN OARNETS 23 4. 1 COLOUR CENTRES 23 4. 2 PARAMAGNETIC DEFECTS 26 5 SAMPLE PREPARATION AND EXPERIMENTAL SET UP. 32 5. 1 SAMPLE PREPARATION. 32 5. 2 SINTERING OF THE POWDERS 32 5. 2. 1 Evaporation effects during sintering 33 5. 3 SOLUBILITY OF Ca, Hg, Zr AND Hf IN YAG 36 5. 4 ELECTRICAL MEASUREMENTS 37 5. 4. 1 Electrodes and electrode effects 40 6 ANALYTICAL TECHNIQUES AND RESULTS 47 6. 1 ELEMENT ANALYSIS 47 6. 2 AUGER ANALYSES 47 7 AL-RICH INCLUSIONS 50 7. 1 CHEMICAL COMPOSITION OF THE INCLUSIONS 51 7. 2 THE SHAPE OF THE Al-RICH INCLUSIONS 52 7. 3 THERMAL STABILITY OF THE INCLUSIONS 54 8 6RAIN BOUNDARIES IN TAB INVESTIOATED BY TEM. 56 8. 1 EXPERIMENTAL 58 6. 2 RESULTS AND DISCUSSION 59 6. 3 TEM-STUDIES DESCRIBED IN LITERATURE 62 9 MICROSTRUCTURE AND MICROSTRUCTURAL CIMNBES INVEST I- SATED BX AC-DISPERSIVE MEASUREMENTS 63 9. 1 INTRODUCTION. 63 9. 2 AC-DISPERSIVE DETECTION OF 6RAIH BOUNDARY PHASES IN YAG-CERAMICS 66 I f 9. 2. 1 Experiments and discussion 66 9.3 NON-LINEAR LEAST SQUARES FIT (NLLSF) OF IMPEDANCE DATA 70 9. 4 TEMPERATURE DEPENDENCE OF GRAIN BOUNDARY AND BULK CONDUCTIVITY 74 9. 4. l Experiments and discussion 74 9. 5 A 240 HOURS ANNEAL EXPERIMENT 76 9. 5. 1 Experiments and discussion 77 9. A PROPERTIES OF YAG CERAMIC QUENCHED FROM 2020 K TO ROOM TEMPERATURE 81 9. 6. 1 Experiments and discussion 82 10 DCrCCT CHEMISTRr OT CA- AND MS-DOPED XAB 87 10. 1 SAMPLE CHARACTERISATION. 87 10. 2 DISPERSED PARTICLES IN A CONDUCTING MATRIX: WAGNERS MODEL 88 10. 3 RESULTS AND DISCUSSION 90 10. 4 THE TEMPERATURE DEPENDENCE OF CONDUCTIVITY 100 10. 5 CONCLUSION 102 It DEFECT CHEMISTRr ©T ZR-DOPED XAB 103 11. 1 SAMPLE CHARACTERISATION 104 11. 2 RESULTS AND DISCUSSION 105 11. 2. 1 The defect model for Zr-doped YAG 106 11. 3 THE TEMPERATURE DEPENDENCE OF THE CONDUCTIVITY 109 11. 5 CONCLUSION. 110 12 UNDOPCD POLrCRySTAtL INC TAB 112 12. 1 SAMPLE CHARACTERISATION 112 12. 2 RESULTS AND DISCUSSION 112 12. 3 CONCLUSION 115 13 VNDOPED SINBLE CRYSTALLINE TAB 115 13. 1 SAMPLE CHARACTER I SAT I ON 115 13. 2 EXPERIMENT AND DISCUSSION 116 1 3. 3 CONCLUSION. 118 14 INTERACTION ©T TAB WITH HTDROBEN CONTAININB ATMOSPHERES 119 14. 1 INTRODUCTION. 119 14. 2 INFRARED BANDS IN ANNEALED SINGLE CRYSTALLINE YAG 120 14. 3 ELECTRICAL TRANSPORT PROPERTIES OF YAG IN A Hs/HpO AMBIENT 122 14.3. 1 The activation energies for a in YAG: Zr in H2/H20 123 14. 3. 2 The activation energies for o in undoped YAG in H2/H20 124 14.3.4 The complex impedance behaviour of polycrystal 1 lne YAG in a H2/H2O-atmosphere 126 14. 4 CONCLUSION. 127 15 SINTER ADDITIVES MMD MICROSTRUCTURE 129 15. 1 EXPERIMENTS 129 15. 2 RESULTS AND DISCUSSION 130 15. 3 EXAMPLE OF EXAGGERATED GRAIN GROWTH 133 v tti: tt > ^ 15. 4 CONCLUSION 135 16 COMPUTER SIMULATION Of IONIC DEFECTS 136 16. 1 THEORY OF DEFECT CALCULATIONS-A SKETCH 136 16. 2 THE PERFECT LATTICE PROPERTIES OF YAG 138 16. 3 THE BASIC POINT DEFECT FORMATION ENERGIES 140 16. 4 FOREIGN CATIONS IN YIG AND YAG 141 16. 5 OXIDATION/REDUCTION PROCESSES IN YAG AND YIG 142 16. 6 THE DISSOLUTION OF CaO IN YAG 146 16. 6. 1 The energy for substituting Y by Ca 146 16. 6. 2 The solution enthalpy of CaO In YAG 147 16. 6. 3 Clustering effects 149 16. 7 THE DISSOLUTION OF MgO IN YAG 149 1 6. 0 SADDLE POINT ENERGIES 160 16. 8. 1 Oxygen juaps 150 16. 8. 2 The spatial dependence of the saddle point energies 153 16. 8. 3 AlumlnluB Jumps 155 16. 9 CONCLUSION 155 APPENDIX 1 167 APPENDIX 2 165 SUMHART 166 SAMENVATTINB 168 CURRICULUM VITAE 169 STELLIHGEH 1. The opinion that sintering of solid particles is a vary alow process at room temperature hardly describes reality. S.R.Rao "Surface Phenomena", Hutchinson Educational Ltd., (1972), p. 70 2. The autors conclude that high meat western diet enhances the excretion of the trace element Hn; they did not pay attention to the fact that several components of this diet contain re- latively high amounts of this trace element. Furthermore, tes- ting only 14 men and women does not lead to reliable results. J. H. Johnson, dies, H. M. Fox, Hutr. Rep. Intern, ,3ft, (1966), 1299 3. "YAG-laser: abbreviation for yttrlum-argon-laser" - this statement is not true. Pschyrembel Kllnlsches wbrterbuch, p. 1827, 255. Auflage 1985, W. de Qruyter, Berlin 4. The authors give the temperature dependence of the di- electric from temperature for 92X pure alumina, con- cluding that this is the loss of alumina Itself. They do not take into consideration that liquid phases are presum- ably responsible for loss in highly Impure materials. H. FuKushlma, T. Tamanake, H. Hatsul, Hat. Res. Soc. Symp. Proc. , 121, (1966), 267 5. The extracts of Caplscum Annuum (chile pods), which was proved to serve as a D^-sensltlve coating for a piezo-crystal de- tector is in no way characterized. The speculation that vita- mine c plays an important role is is doubtful. L. H. Webber, a a. Oul 1 baul t, Anal. Cham. , 4ft, (1976). 2244 6. Jeh and Sacks report that they have sintered fine grained alumina powders to 99.5Z density at 1160°C with average grain size of 0.25 pm after 2h sintering time. Hlcrostructural analysis was done on samples which were thermally etched at 116O°C for 4 h. So they investigated samples which were sintered In fact 6 h. T. S. Yeh, H. D. Sacks, J. Am. Ceram. Soc. , H, (1966), 644 7. Die Autonomle, die sle (die Kunst) erlangte, nachitem. sle lhre kultlsche Funktlon und dessen Hachbllder abschilttelte, zehrt von der Idee der Humanltat - Theodor V. Adorno, "Asthe- tlsche Theorle", Suhrkamp Verlag, 1977. In this stage In the development of arts In Hunan society It Is commercialisation and not humanity which acts as a "fertilizer". 8. Sintering behaviour of an alumina powder with a maximum particle diameter of 0. 2 pm is compared with the unclassi- fied powder. Ho particle size distribution of the unclassi- fied powder Is given. T. R. Gattuso, H. E. Bowen, Adv. Cer. , 1£, (1987), 644 9. The electrical conductivity of AlB containing various oxide additives was investigated by dc-methods. Ho frequency dis- persion is given. Due to the fact that AlH-gralns are covered by a highly insulating alumlna-fllm, these results are doubt- ful. H. Zufelquar, A. Kumar, J. Hater. Scl. ,££, (1967), 4056 10. It is not plausible that the misfit strain of a Ca2+-lon on a Al3*-position in AI2O3 Is about 1.5 eV/atom as stated by Cook and Schrott. It must be much higher because the defect Ca^t/ has a charge. R. F. Cook. A. Q. Schrott, J. Am. Ceram. Soc. H, (1966), SO 11. C00K and Schrott considered the segregation of Ca to grain boundaries In alumina; they conclude that the misfit strain Is the driving force for this process. The authors should better consider the solution enthalpy of CaO In alumina as well as the difference In energy for CaA]'(bulk) and CaAJ (grain boundary) R. P. Cook, A. fl. Schrott, J. Am. Ceram. Soc. , 2i, (1966). 50 12. Rotman and Tuller do not consider the possibility that at low oxygen pressure Zr** is reduced. S. R. Rotman, H« L. Tul ler, Hat. Res. Soc. Symp. Proc. £0_, (1966) 413 13. The diffusion In KgSiO3 Is considered at a 3750 K (I) and 37 QPa; a perfect lattice simulation may not lead to accurate results. B. Kapusta, H. (Millope, Phil. Hag. A 3ft, (1966) 6O9 14. The fact that Ahmed et al. found slightly different trans- ition temperatures of 90 and 93 I for conventionally and microwave sintered 1-2-3 superconductors is far from being significant. 1. Ahmed, <3. T. Chandler, D,B. Clark, Hat. Res. Soc. Symp. Proc. 124. (1986), 239. INTRODUCTION Tills thesis is centered around the synthetic garnets, a class of materials with the same crystallographic structure as the natu- rally occurring garnet minerals.
Recommended publications
  • CHAPTER 8: Diffusion

    CHAPTER 8: Diffusion

    1 Chapter 8 CHAPTER 8: Diffusion Diffusion and ion implantation are the two key processes to introduce a controlled amount of dopants into semiconductors and to alter the conductivity type. Figure 8.1 compares these two techniques and the resulting dopant profiles. In the diffusion process, the dopant atoms are introduced from the gas phase of by using doped-oxide sources. The doping concentration decreases monotonically from the surface, and the in-depth distribution of the dopant is determined mainly by the temperature and diffusion time. Figure 8.1b reveals the ion implantation process, which will be discussed in Chapter 9. Generally speaking, diffusion and ion implantation complement each other. For instance, diffusion is used to form a deep junction, such as an n-tub in a CMOS device, while ion implantation is utilized to form a shallow junction, like a source / drain junction of a MOSFET. Boron is the most common p-type impurity in silicon, whereas arsenic and phosphorus are used extensively as n-type dopants. These three elements are highly soluble in silicon with solubilities exceeding 5 x 1020 atoms / cm3 in the diffusion temperature range (between 800oC and 1200oC). These dopants can be introduced via several means, including solid sources (BN for B, As2O3 for As, and P2O5 for P), liquid sources (BBr3, AsCl3, and POCl3), and gaseous sources (B2H6, AsH3, and PH3). Usually, the gaseous source is transported to the semiconductor surface by an inert gas (e.g. N2) and is then reduced at the surface. 2 Chapter 8 Figure 8.1: Comparison of (a) diffusion and (b) ion implantation for the selective introduction of dopants into a semiconductor substrate.
  • Improving the Scintillation Performance of Ksr2i5:Ce3+ Through Exploration of Activator Concentration and Growth Conditions

    Improving the Scintillation Performance of Ksr2i5:Ce3+ Through Exploration of Activator Concentration and Growth Conditions

    University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Masters Theses Graduate School 5-2019 Improving the Scintillation Performance of KSr2I5:Ce3+ through Exploration of Activator Concentration and Growth Conditions Eleanor Paige Comer University of Tennessee, [email protected] Follow this and additional works at: https://trace.tennessee.edu/utk_gradthes Recommended Citation Comer, Eleanor Paige, "Improving the Scintillation Performance of KSr2I5:Ce3+ through Exploration of Activator Concentration and Growth Conditions. " Master's Thesis, University of Tennessee, 2019. https://trace.tennessee.edu/utk_gradthes/5414 This Thesis is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Masters Theses by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a thesis written by Eleanor Paige Comer entitled "Improving the Scintillation Performance of KSr2I5:Ce3+ through Exploration of Activator Concentration and Growth Conditions." I have examined the final electronic copy of this thesis for form and content and recommend that it be accepted in partial fulfillment of the equirr ements for the degree of Master of Science, with a major in Nuclear Engineering. Charles L. Melcher, Major Professor We have read this thesis and recommend its acceptance: Mariya Zhuravleva, Eric Lukosi Accepted for the Council: Dixie L. Thompson Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) Improving the Scintillation Performance of KSr2I5:Ce3+ through Exploration of Activator Concentration and Growth Conditions A Thesis Presented for the Master of Science Degree The University of Tennessee, Knoxville Eleanor Paige Comer May 2019 Copyright © 2019 by Eleanor P.
  • Contactless, Nondestructive Determination of Dopant Profiles Of

    Contactless, Nondestructive Determination of Dopant Profiles Of

    www.nature.com/scientificreports OPEN Contactless, nondestructive determination of dopant profles of localized boron-difused regions in Received: 11 November 2018 Accepted: 9 July 2019 silicon wafers at room temperature Published: xx xx xxxx Hieu T. Nguyen , Zhuofeng Li, Young-Joon Han , Rabin Basnet, Mike Tebyetekerwa , Thien N. Truong , Huiting Wu, Di Yan & Daniel Macdonald We develop a photoluminescence-based technique to determine dopant profles of localized boron- difused regions in silicon wafers and solar cell precursors employing two excitation wavelengths. The technique utilizes a strong dependence of room-temperature photoluminescence spectra on dopant profles of difused layers, courtesy of bandgap narrowing efects in heavily-doped silicon, and diferent penetration depths of the two excitation wavelengths in silicon. It is fast, contactless, and nondestructive. The measurements are performed at room temperature with micron-scale spatial resolution. We apply the technique to reconstruct dopant profles of a large-area (1 cm × 1 cm) boron-difused sample and heavily-doped regions (30 μm in diameter) of passivated-emitter rear localized-difused solar cell precursors. The reconstructed profles are confrmed with the well- established electrochemical capacitance voltage technique. The developed technique could be useful for determining boron dopant profles in small doped features employed in both photovoltaic and microelectronic applications. An attractive approach for improving light-to-electricity power conversion efciencies of crystalline silicon (c-Si) solar cells is to minimize surface areas of heavily-doped layers. Tis is due to the high recombination-active nature of the heavily-doped layers, causing a signifcant loss of photo-induced electrons and holes. Several solar cell designs employing this concept have been proved to achieve efciencies over 24% such as interdigitated back-contact (IBC)1–3 and passivated-emitter rear localized-difused (PERL)4–6 cell structures.
  • (YAG) Laser Capsulotomy Reference Number: CP.VP.65 Coding Implications Last Review Date: 12/2020 Revision Log

    (YAG) Laser Capsulotomy Reference Number: CP.VP.65 Coding Implications Last Review Date: 12/2020 Revision Log

    Clinical Policy: Yttrium Aluminium Garnet (YAG) Laser Capsulotomy Reference Number: CP.VP.65 Coding Implications Last Review Date: 12/2020 Revision Log See Important Reminder at the end of this policy for important regulatory and legal information. Description This policy describes the medical necessity requirements for yttrium aluminium garnet (YAG) laser capsulotomy. Policy/Criteria I. It is the policy of health plans affiliated with Centene Corporation® (Centene) that YAG laser capsulotomy is medically necessary for the following indications: A. Posterior capsular opacification following cataract surgery resulting in best corrected visual acuity of 20/30 or worse associated with symptoms of blurred vision, visual distortion or glare affecting activities of daily living; B. Contraction of the posterior capsule with resulting displacement of the intraocular lens; C. Posterior capsular opacification resulting in best corrected visual acuity of 20/25 or worse, reducing the ability to evaluate and treat retinal detachment. Background YAG capsulotomy is the incision of an opaque posterior lens capsule in an aphakic or pseudophakic eye. This incision allows the capsule to retract and no longer serve as an obstruction to the passage of light through the media to the retina. The incision is performed with YAG laser. The eye examination must confirm the diagnosis of posterior capsular opacification and excludes other ocular causes of functional impairment by one of the following methods: The eye examination should demonstrate decreased light transmission (visual acuity worse than 20/30 or 20/25 if the procedure is performed to assist in the diagnosis and treatment of retinal detachment). Manifest refraction must be recorded with decrease in best-corrected visual acuity.
  • O/M Ratio Measurement in Pure and Mixed Oxide Fuels-Where Are We Now?

    O/M Ratio Measurement in Pure and Mixed Oxide Fuels-Where Are We Now?

    FR0200369 K -_£*- to 0/M RATIO MEASUREMENT IN PURE AND MIXED OXIDE FUELS - WHERE ARE WE NOW? J. RUBIN (1), K. CHIDESTER (2), M. THOMPSON (2), Los Alamos National Laboratory (1) Mail Stop E-574, (2) Mail Stop E530, Los Alamos, New Mexico 87545-USA E-mail: [email protected] KEYWORDS: Chemistry, Methods, Fuel INTRODUCTION The scale-down in the US and Russian nuclear weapons stockpiles has produced a surplus of weapons grade plutonium and highly enriched uranium. According to a recent National Academy of Sciences Report "Some 10,000-20,000 warheads in the United States and at least a similar number in the former Soviet Union are likely to fall into this [excess] category, depending on the ultimate scope of reductions and decisions concerning the size of non-deployed reserves. These excess nuclear weapons on the two sides could contain well over 100 metric tons of plutonium, and perhaps 1,000 metric tons of HEU, much of which may also be declared excess to military needs."[1] This excess weapons Pu is considered to be a threat for potential proliferation and various disposal options have been examined. The currently favored disposition routes for surplus weapons-grade Pu are (1) incorporation into mixed-oxide fuel (MOX), and "burning" in civilian nuclear reactors, and (2) immobilization of the Pu together with intensely radioactive fission products in glass. The use of MOX as a nuclear reactor fuel is well established, particularly in Europe and Japan. There are, however, no MOX fuel fabrication facilities in the US, owing to the fact that there are no domestic electricity generators using MOX fuel.
  • Colourless Gemstones

    Colourless Gemstones

    GEMS THE gem DeteCTIVE: COLOURLess gemstONes superseded in the 1970s by a man-made gemstone called cubic zirconia that is still the most popular and common diamond imitation in modern jewellery due to its low cost, high dispersion and good hardness (8.5 on Mohs scale). Another man-made gemstone called synthetic Moissanite was introduced as a diamond simulant in the late 1990s. Although TED A synthetic Moissanite tests positive on a FFILI A diamond tester, it is easily distinguished from diamond by a property called double refraction, detected using a 10x loupe. This property is also displayed by zircon, a natural CCREESH, O’NEILS O’NEILS CCREESH, gemstone with a sub-adamantine lustre. M N N A Complicating the process of identification are treatments that may affect the value of gemstones. For example, a laser may be used to drill down to a dark diamond inclusion and remove it using acid in a process called GE COURTESY OF BREND OF COURTESY GE laser drilling. Also common is fracture filling, ma I where a high refractive-index lead glass is used to fill surface-reaching fractures to make Sparkling, colourless gemstones may People love to assume that their great ALTHOUGH them less visible. Fortunately, both of these appear similar to the naked eye but they grandma’s solitaire engagement ring SYNTHETIC treatments are easily identified using a loupe can vary significantly in identity, rarity contained a natural diamond by virtue MOISSANITE or microscope. TESTS POSITIVE and value. Making such distinctions of its age but they should think again. Some off-coloured diamonds may be ON A DIamOND requires the detective skills of a qualified Synthetically-produced sapphire, spinel and TESTER, IT CAN BE whitened using High Pressure High gemmologist.
  • Gain in Polycrystalline Nd-Doped Alumina: Leveraging Length Scales to Create a New Class of High-Energy, Short Pulse, Tunable Laser Materials Elias H

    Gain in Polycrystalline Nd-Doped Alumina: Leveraging Length Scales to Create a New Class of High-Energy, Short Pulse, Tunable Laser Materials Elias H

    Penilla et al. Light: Science & Applications (2018) 7:33 Official journal of the CIOMP 2047-7538 DOI 10.1038/s41377-018-0023-z www.nature.com/lsa ARTICLE Open Access Gain in polycrystalline Nd-doped alumina: leveraging length scales to create a new class of high-energy, short pulse, tunable laser materials Elias H. Penilla1,2,LuisF.Devia-Cruz1, Matthew A. Duarte1,2,CoreyL.Hardin1,YasuhiroKodera1,2 and Javier E. Garay1,2 Abstract Traditionally accepted design paradigms dictate that only optically isotropic (cubic) crystal structures with high equilibrium solubilities of optically active ions are suitable for polycrystalline laser gain media. The restriction of symmetry is due to light scattering caused by randomly oriented anisotropic crystals, whereas the solubility problem arises from the need for sufficient active dopants in the media. These criteria limit material choices and exclude materials that have superior thermo-mechanical properties than state-of-the-art laser materials. Alumina (Al2O3)isan ideal example; it has a higher fracture strength and thermal conductivity than today’s gain materials, which could lead to revolutionary laser performance. However, alumina has uniaxial optical proprieties, and the solubility of rare earths (REs) is two-to-three orders of magnitude lower than the dopant concentrations in typical RE-based gain media. We present new strategies to overcome these obstacles and demonstrate gain in a RE-doped alumina (Nd:Al2O3) for the first time. The key insight relies on tailoring the crystallite size to other important length scales—the wavelength of 1234567890():,; 1234567890():,; 1234567890():,; 1234567890():,; light and interatomic dopant distances, which minimize optical losses and allow successful Nd doping.
  • Catalysis Science of Bulk Mixed Oxides Israel E

    Catalysis Science of Bulk Mixed Oxides Israel E

    Perspective pubs.acs.org/acscatalysis Catalysis Science of Bulk Mixed Oxides Israel E. Wachs* and Kamalakanta Routray Operando Molecular Spectroscopy and Catalysis Laboratory, Department of Chemical Engineering, Lehigh University, Bethlehem, Pennsylvania 18015, United States ABSTRACT: Bulk mixed oxide catalysts are widely used for various applications (selective oxidation catalysts, electro- catalysts for solid oxide fuel cells, and solid oxide electrolyzers for the production of hydrogen), but fundamental under- standing of their structure−performance relationships have lagged in the literature. The absence of suitable surface composition and surface structural characterization techniques and methods to determine the number of catalytic active sites, with the latter needed for determination of specific reaction rates (e.g., turnover frequency (1/s)), have hampered the development of sound fundamental concepts in this area of heterogeneous catalysis. This Perspective reviews the traditional concepts that have been employed to explain catalysis by bulk mixed oxides (molybdates, vanadates, spinels, perovskites, and several other specific mixed oxide systems) and introduces a modern perspective to the fundamental surface structure−activity/selectivity relationships for bulk mixed oxide catalysts. The new insights have recently been made available by advances in surface characterization techniques (low-energy ion scattering, energy-resolved XPS, and CH3OH-IR) that allow for direct analysis of the outermost surface layer of bulk mixed metal oxide catalysts. The new findings sound a note of caution for the accepted hypotheses and concepts, and new catalysis models need to be developed that are based on the actual surface features of bulk mixed oxide catalysts. KEYWORDS: catalysts, oxides, bulk, one component, mixed, vanadates, molybdates, spinels, perovskites, spectroscopy, in situ, Raman, IR, TPSR, LEIS, SIMS, XPS I.
  • Toxicological Profile for Zinc

    Toxicological Profile for Zinc

    TOXICOLOGICAL PROFILE FOR ZINC U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES Public Health Service Agency for Toxic Substances and Disease Registry August 2005 ZINC ii DISCLAIMER The use of company or product name(s) is for identification only and does not imply endorsement by the Agency for Toxic Substances and Disease Registry. ZINC iii UPDATE STATEMENT A Toxicological Profile for Zinc, Draft for Public Comment was released in September 2003. This edition supersedes any previously released draft or final profile. Toxicological profiles are revised and republished as necessary. For information regarding the update status of previously released profiles, contact ATSDR at: Agency for Toxic Substances and Disease Registry Division of Toxicology/Toxicology Information Branch 1600 Clifton Road NE Mailstop F-32 Atlanta, Georgia 30333 ZINC vi *Legislative Background The toxicological profiles are developed in response to the Superfund Amendments and Reauthorization Act (SARA) of 1986 (Public law 99-499) which amended the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA or Superfund). This public law directed ATSDR to prepare toxicological profiles for hazardous substances most commonly found at facilities on the CERCLA National Priorities List and that pose the most significant potential threat to human health, as determined by ATSDR and the EPA. The availability of the revised priority list of 275 hazardous substances was announced in the Federal Register on November 17, 1997 (62 FR 61332). For prior versions of the list of substances, see Federal Register notices dated April 29, 1996 (61 FR 18744); April 17, 1987 (52 FR 12866); October 20, 1988 (53 FR 41280); October 26, 1989 (54 FR 43619); October 17, 1990 (55 FR 42067); October 17, 1991 (56 FR 52166); October 28, 1992 (57 FR 48801); and February 28, 1994 (59 FR 9486).
  • Effects of Dopant Additions on the High Temperature Oxidation Behavior of Nickel-Based Alumina- Forming Alloys

    Effects of Dopant Additions on the High Temperature Oxidation Behavior of Nickel-Based Alumina- Forming Alloys

    Effects of Dopant Additions on the High Temperature Oxidation Behavior of Nickel-based Alumina- forming Alloys by Talia L. Barth A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Materials Science and Engineering) in the University of Michigan 2020 Doctoral Committee: Professor Emmanuelle Marquis, Chair Assistant Professor John Heron Professor Krishna Garikipati Professor Alan Taub Talia L. Barth [email protected] ORCID iD: 0000-0001-8266-7447 © Talia L. Barth 2020 ACKNOWLEDGEMENTS I would like to first offer my heartfelt thanks to my advisor, Professor Emmanuelle Marquis, without whom this work would not have been possible. Her exceptional mentorship has had an immense impact on my development as a researcher and a person, and her support and guidance along my journey have been invaluable. I would also like to express my appreciation for the rest of my committee, Professor Alan Taub, Assistant Professor John Heron, and Professor Krishna Garikipati for providing valuable advice and support for the completion of this work. I am grateful to the staff at the Michigan Center for Materials Characterization (MC)2, especially to Allen Hunter, Bobby Kerns, Haiping Sun, and Nancy Muyanja whose training enabled me to work confidently on the characterization instruments essential to this dissertation, and were always eager to lend their expertise with data collection and analysis. My colleagues in the Marquis group over the years were also important to this work and to my professional and personal development. I would like to thank Kevin Fisher, Ellen Solomon, Elaina Reese, and Peng-Wei Chu for getting me up to speed in the lab and for being there as mentors and friends in my first years as a grad student.
  • Crystal Preferred Orientations of Garnet

    Crystal Preferred Orientations of Garnet

    Journal of Structural Geology 26 (2004) 2089–2102 www.elsevier.com/locate/jsg Crystal preferred orientations of garnet: comparison between numerical simulations and electron back-scattered diffraction (EBSD) measurements in naturally deformed eclogites David Mainpricea,*,Je´roˆme Bascoua, Patrick Cordierb, Andre´a Tommasia aLaboratoire de Tectonophysique, CNRS & Universite´ Montpellier II, France bLaboratoire de Structure et Proprie´te´s de l’Etat Solide, CNRS & Universite´ Lille I, France Received 26 March 2003; received in revised form 8 April 2004; accepted 24 April 2004 Available online 10 July 2004 Abstract Observations of dislocations, sub-grains and elongated crystal shapes support plastic deformation of garnet in laboratory experiments and naturally deformed eclogites. To evaluate the crystal preferred orientations (CPO) of garnet formed in axial shortening, pure shear and simple shear, we performed numerical simulations of CPO development during plastic flow using the visco-plastic self-consistent model. As input for the models we use the slip systems determined by transmission electron microscopy using experimentally deformed specimens. Although in garnet 66 slip systems are available, slip on the k111l{110} system provides over 86% of the total strain in the simulations. Characteristic CPO distributions are produced for the three deformation paths, with the CPO being strongest for axial shortening and weakest for simple shear. Compared with low-symmetry minerals, the pole figure densities of garnet, which has cubic symmetry, are weak. k100l axes tend to align with the shortening direction in all three deformation modes. The simulations are compared with CPO of naturally deformed garnet from nine eclogite samples from the Alps, Norway, and Mali, which contain 20–40% garnet.
  • Pulsed Laser Deposition of High-Quality Μm-Thick YIG Films on YAG

    Pulsed Laser Deposition of High-Quality Μm-Thick YIG Films on YAG

    Pulsed laser deposition of high-quality μm-thick YIG films on YAG A. Sposito,1,* T. C. May-Smith,1 G. B. G. Stenning,2 P. A. J. de Groot,2 and R. W. Eason1 1Optoelectronics Research Centre, University of Southampton, SO17 1BJ, Southampton, United Kingdom 2Physics and Astronomy, University of Southampton, SO17 1BJ, Southampton, United Kingdom *[email protected] Abstract: We report the epitaxial growth of high-quality μm-thick yttrium iron garnet (YIG) films on yttrium aluminium garnet (YAG) substrates by pulsed laser deposition (PLD). The effects of substrate temperature and oxygen pressure on composition, crystallinity, optical transmission and ferromagnetic resonance (FMR) linewidth have been investigated. An FMR linewidth as low as 1.75 mT at 6 GHz was achieved by depositing YIG on YAG substrates with (100) orientation at a substrate temperature of ~1600 K and with oxygen pressure of ~1 Pa. ©2013 Optical Society of America OCIS codes: (160.3820) Magneto-optical materials; (310.1860) Deposition and fabrication. References and links 1. R. W. Eason, Pulsed Laser Deposition of Thin Films – Applications-led Growth of Functional Materials (Wiley Interscience, 2007). 2. N. A. Vainos, C. Grivas, C. Fotakis, R. W. Eason, A. A. Anderson, D. S. Gill, D. P. Shepherd, M. Jelinek, J. Lancok, and J. Sonsky, “Planar laser waveguides of Ti:sapphire, Nd:GGG and Nd:YAG grown by pulsed laser deposition,” Appl. Surf. Sci. 127-129, 514–519 (1998). 3. H. Dötsch, N. Bahlmann, O. Zhuromskyy, M. Hammer, L. Wilkens, R. Gerhardt, P. Hertel, and A. F. Popkov, “Applications of magneto-optical waveguides in integrated optics: review,” J.