Growing Anatase and Rutile Titania on C-Cut Sapphire Using Pulsed-Laser Deposition

Total Page:16

File Type:pdf, Size:1020Kb

Growing Anatase and Rutile Titania on C-Cut Sapphire Using Pulsed-Laser Deposition Growing Anatase and Rutile Titania on c-cut Sapphire using Pulsed-Laser Deposition by Alexandra V. Gordienko, inener-fizik po special~nosti fizika kondensirovannogo sostoni vewestva i nanosistem A Thesis In Physics Submitted to the Graduate Faculty of Texas Tech University in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE Approved Anthony B. Kaye Chair of Committee David Lamp Charles Myles Mark Sheridan Dean of the Graduate School December, 2016 Copyright 2016, Alexandra Gordienko Texas Tech University, Alexandra V. Gordienko, December 2016 Acknowledgments This research made use of the TTU College of Arts & Sciences Microscopy Center. I would like to thank Dr. D. Unruh for his assistance with a number of aspects related to XRD. I would like to thank Keller Andrews for his thoughtful discussions, and Dr. A. Kaye for his mentorship and encouragement throughout the thesis process. Finally, I would like to thank Dennis and Brooke Harris as well as Vladimir and Svetlana Gordienko for their daily support. ii Texas Tech University, Alexandra V. Gordienko, December 2016 Contents Acknowledgments ................................ ii Abstract ...................................... v List of Tables ................................... vi List of Figures .................................. vii 1. Introduction .................................. 1 1.1 Introduction . 1 1.2 Overview . 3 1.3 My Contribution to the Field . 4 2. Producing the Different Phases of TiO2 ................ 6 2.1 Major Production Methodologies . 6 2.1.1 Techniques in Common . 6 2.1.2 Sol-gel techniques . 8 2.1.3 Sputtering . 10 2.1.4 Chemical Vapor Deposition . 11 2.1.5 Pulsed-Laser Deposition . 13 2.1.6 Other Techniques . 15 2.2 Film Growth Considerations . 17 2.2.1 Crystallographic Match and Cost . 18 2.3 A Brief Review of Titania Production Techniques . 22 2.4 Pulsed-Laser Deposition: Our System, Methods, and Results . 23 2.4.1 Our System . 23 iii Texas Tech University, Alexandra V. Gordienko, December 2016 2.4.2 Methodology . 24 2.4.3 Characterization . 28 2.4.3.1 Atomic Force Microscopy . 28 2.4.3.2 Scanning Electron Microscopy . 31 2.4.3.3 Raman Spectroscopy . 31 2.4.3.4 XRD . 35 2.4.4 Final Production Protocols . 39 3. Summary and Future Work ........................ 40 3.1 Summary . 40 3.2 Future Work . 40 Bibliography ................................... 42 iv Texas Tech University, Alexandra V. Gordienko, December 2016 Abstract In this thesis, I present a review of the growth of tetragonal phases of titanium dioxide on different substrates. I also report a pulsed-laser deposition growth proto- col that facilitates the growth of both anatase and rutile phases of titania without changing the substrate or target material. Finally, I also demonstrate the develop- ment of the first recipe for growth of anatase titania on a sapphire substrate. v Texas Tech University, Alexandra V. Gordienko, December 2016 List of Tables 2.1 Pulsed-Laser Deposition Variables . 14 2.2 Comparison of Thin-Film Growth Techniques . 16 2.3 Lattice Matches to Typical Substrate Materials . 20 2.4 Example Thin Film Results . 26 2.5 Raman Shift Peak Identification . 34 2.6 TiO2 film growth conditions . 39 vi Texas Tech University, Alexandra V. Gordienko, December 2016 List of Figures 2.1 The general process of film producing via the sol-gel technique . 9 2.2 Schematic of sputtering system used to create thin films. 10 2.3 Schematic of a typical low pressure hot wall chemical vapor deposition reactor used in coating silicon substrates. 12 2.4 Schematic representation of the fundamental transport and reaction steps underlying metalorganic chemical vapor deposition. 12 2.5 Schematic representation of the Kaye Research Group pulsed-laser depo- sition system. 14 2.6 Sketch of how an atomic force microscope works . 30 2.7 Raman spectra of thin-film samples. 33 2.8 X-ray diffraction patterns for the rutile (top, red) and anatase (bottom, blue) films. 36 2.9 X-ray diffraction pattern of the mixed-phase film from Sample 5. 38 vii Texas Tech University, Alexandra V. Gordienko, December 2016 Chapter 1. Introduction 1.1 Introduction Titanium dioxide (titania; TiO2) is a material that has been studied carefully over the last 100 years (Vegard, 1916). Since its first production, titania has become one of the most widely used white pigments. Pearlescent-effect pigments are based on TiO2, and when combined with metallic pigments, it is often used in car paints, since the combination of titania-based pearlescent pigments and metallic pigments creates an illusion of optical depth. Titania pigments are also used in decorative objects that are intended to imitate natural pearls, cosmetics, and in critical areas of security printing. Titania pigments are also used in almost all white paint and most red-colored candy. With so many applications, TiO2 has become a popular material to study. In 1972, Fujishima and Honda discovered the possibility to split water using TiO2 electrodes. Since its initial publication (Fujishima and Honda, 1972), the Fujishima and Honda paper has been cited over 18,000 times, and it has changed the landscape of photocatalytic science and industry: a whole range of new applications has now been discovered. Among new applications are: using TiO2 as self-cleaning coatings (i.e., when the coating breaks down the organic dirt after exposure to UV light and makes the surface hydrophilic so water spreads evenly on the glass (Roméas et al., 1999); as coatings that are used in environmental applications to clean both air and water (Di Fonzo et al., 2008; Lin et al., 2008); as components of various sensor devices (Bao et al., 2008; György et al., 2005); as a gate dielectric in MOSFET technologies 1 Texas Tech University, Alexandra V. Gordienko, December 2016 (Kim et al., 2006; Xie et al., 2010); and, as the basis for energy-efficient solar cells (Mincuzzi et al., 2009; Park et al., 2000). Titanium dioxide has three stable crystallographic forms, two of which, rutile and anatase, are tetragonal; the third phase (brookite) is orthorhombic. It is well established that properties of titania, and hence the performance of coatings and devices based on it, are different depending upon the crystallographic phase of the titania. For instance, the rutile phase is a more stable form and it scatters light more efficiently (Thiele and French, 1998). Anatase is used in production of solar cells because of its surface chemistry (Hoffmann et al., 1995; Park et al., 2000), and because this phase has roughly twice the photocatalytic power of the rutile phase (Luttrell et al., 2014). For that same reason, anatase is the preferred crystallographic phase for gas- sensing applications since photocatalytic activity is shown to enhance the sensitivity of gas sensors (Yang et al., 2003). Rutile titania could potentially become a better choice for use in solar cells because it is a less expensive material to produce [in fact, most production techniques of synthetic titania yield rutile as a result (Mo and Ching, 1995)], and it scatters light more effectively than anatase. However, the annealing procedure(s) can significantly affect the photocatalytic properties of rutile films (Luttrell et al., 2014), so the growth protocols and the substrate materials selected for the production of titania are critically important. Additionally, the dielectric properties of titania are directly related to the ratio between anatase and rutile phases present in the film. Specifically, dielectric constants increase with the increase of rutile to anatase ratio (Kim et al., 2006), which is significant when titania is used in MOSFET technologies. 2 Texas Tech University, Alexandra V. Gordienko, December 2016 1.2 Overview Over the last 100 years, a number of methods have been developed to produce titania, each one optimized for the final form required. Each of these methods will be summarized and compared to each other in Chapter 2., below. We used pulsed laser deposition as our growth method, and the principal goal of this study was to grow pure samples of both tetragonal phases of titania – anatase and rutile – using the same substrate and the same laser target. Because c-cut sapphire is one of the most commonly used in optical applications, and because sapphire is an excellent crystallographic match with rutile titania, we elected to use sapphire as our substrate. This obviously means that because the anatase phase has significantly different crystallographic parameters, it requires significantly different growth conditions compared to those used to grow the rutile phase. The impetus of this study was two-fold: First, a colleague has suggested growing layered films of TiO2, VO2, and TiO2 to studying how the optical and electrical properties of stack varied from simple VO2 films. From prior work, we know that c-cut sapphire is a substrate that shows both excellent switching amplitude and a very sharp (almost square) transition, so it was natural to choose this substrate for the production of the layered composite material. Since we do not know how each crystallographic phase of titania would affect the properties of the resulting system, we were interested in growing both phases of titania on this substrate. A literature review suggested that even though there are certain parameters that are known to be ideal for anatase and rutile growth on different substrates (e.g., glass, Si, and SiO2), growth of titania films on sapphire always lead the growth of the rutile phase. The second reason for this study was to test our understanding of crystallographic 3 Texas Tech University, Alexandra V. Gordienko, December 2016 growth using the pulsed-laser deposition technique, and specifically, if we were able to selectively grow each phase without changing the substrate or the laser target. Once proven, these techniques and procedures could be applied to other, more complex materials in which the crystallographic phase plays an even more critical role (e.g., La2CuO4 and similar materials).
Recommended publications
  • Electroceramics: Characterization by Impedance Spectroscopy
    ADVANCED MATERIALS Ferroelectric Ceramics Electroceramics : Grain Boundary Capacitances Ceramic Electrolytes Characterization by Surface Layers on Glasses Impedance Spectroscopy Ferromagnetic Ceramics By John T. S. Irvine,* Derek C. Sinclair,* and Anthony R. West * Electroceramics are advanced materials whose properties In order to characterize the microstructures and properties and applicationsdepend on the close control of structure, com- of electroceramics, techniques are required that can probe or position, ceramic texture, dopants and dopant (or defect) dis- distinguish between the different regions of a ceramic. Elec- tribution. Impedance spectroscopy is a powerful technique for tron microscopy with an analytical facility is, of course, the unravelling the complexities of such materials, which functions most direct method fo r both microstructural characteriza- by utilizing the different frequency dependences of the constit- tion and for determining compositional variations within a uent components for their separation. Thus, electrical inhomo- solid. Corresponding measurements of microscopic electri- geneities in ceramic electrolytes, electrode/electrolyte inter- cal properties are possible in principle, as shown by the ele- faces, surface layers on glasses, ferroelectricity, positive gant work of Dimos et al. on the effect of grain orientation temperature coefficient of resistance behavior and even ferri- mismatch on critical current densities in ceramic supercon- magnetism can all be probed, successfully, using this tech- ductor~.[~]Such
    [Show full text]
  • Piezoelectric Crystal Experiments for High School Science and En- Gineering Students
    Paper ID #14540 MAKER: Piezoelectric Crystal Experiments for High School Science and En- gineering Students Mr. William H. Heeter, Porter High School Engineering Dept. My name is William (Bill) Heeter. I graduated from Texas A&M with an Engineering degree in 1973. I worked in Industrial Distribution for over 30 years before becoming a high school pre-engineering teacher. I have been teaching engineering and technology for the past 13 years. I have been a Master Teacher for ”Project Lead the Way”, CTE co-Director, CTE Building Chair, Technology Teacher. My students have received many awards and college scholarships. One group of students received a provisional U.S. Patent. Several students have seen their work actually produced by industry, including the ordering touch screens used by Bucky’s. Dr. Sheng-Jen ”Tony” Hsieh, Texas A&M University Dr. Sheng-Jen (”Tony”) Hsieh is a Professor in the Dwight Look College of Engineering at Texas A&M University. He holds a joint appointment with the Department of Engineering Technology and the De- partment of Mechanical Engineering. His research interests include engineering education, cognitive task analysis, automation, robotics and control, intelligent manufacturing system design, and micro/nano manufacturing. He is also the Director of the Rockwell Automation laboratory at Texas A&M University, a state-of-the-art facility for education and research in the areas of automation, control, and automated system integration. Dr. Jun Zou, Department of Electrical and Computer Engineering, Texas A&M University Jun Zou received his Ph.D. degree in electrical engineering from the University of Illinois at Urbana- Champaign in 2002.
    [Show full text]
  • Impact of Ferroelectricity
    erroelectric materials are ubiq- Fuitous in electrical and elec- tromechanical components and systems. Ferroelectricity is associated with large dielectric and piezoelectric coefficients, particularly when the composition is adjusted to position the solid near a phase boundary. This characteristic allows high volumetric efficiency dielec- tric charge storage, as well as high dis- placement actuators at modest voltages. The ability to reorient the spontaneous polarization between crystallographically- defined states is essential in allowing poling of ceramic materials to obtain net Impact of piezoelectric or pyroelectric responses. Capacitors The largest industrial use of ferroelectric materials is in ferroelectricity multilayer ceramic capacitors. The poor availability of mica- based crystals during World War II spurred development of By Susan Trolier-McKinstry air- and moisture-stable, high volumetric efficiency dielec- trics. The subsequent dawn of the electronics age led to pro- duction of several trillion BaTiO3-based capacitors around Since the discovery of ferroelectricity 100 years ago, the world on an annual basis, with hundreds to thousands used in each current generation smart phone or computer. ferroelectric materials are everywhere in our electronics-based The size of this market is approximately $6 billion. Among society. Learn how they drive a $7 billion industry. the major capacitor suppliers around the world are Murata, Taiyo Yuden, Samsung Electromechanics, Kyocera (AVX), TDK, Yageo, and Kemet. Medical ultrasound is the second most widely adopted imaging modality in medicine. It works thanks to ferroelectric materials. 22 www.ceramics.org | American Ceramic Society Bulletin, Vol. 99, No. 1 The relatively closely-spaced ferroelectric phase transitions in BaTiO3 enable a high relative permittivity over a broad Before temperature range.
    [Show full text]
  • Electroceramics XIII June, 24Th-27Th 2012 University of Twente, Enschede, the Netherlands
    Electroceramics XIII June, 24th-27th 2012 University of Twente, Enschede, The Netherlands Welcome It’s our pleasure to welcome you to the Electroceramics XIII conference, held in Enschede, the Netherlands, from June 24 – 27, 2012. We wish you a pleasant stay during the conference, which is hosted by the University of Twente. This booklet provides information about your participation in the scientific and social activities of the conference. The aim of this conference is to provide an interdisciplinary forum for researchers, theorists as well as experimentalist on the design, fabrication, theory, analysis and applications of functional materials and (epitaxial) thin films. Electroceramics materials and applications thereof have become an important field of research within materials science. Major breakthroughs in the synthesis of electroceramic materials, in bulk and (epitaxial) thin films, as well as the understanding of the structure-property relation of these materials have been realized in the last decades. This has led to many exciting new concepts, which are nowadays used in many technological applications. The series of Electroceramics conferences have become an important forum to discuss recent advances and emerging trends in this developing field. New research areas have been adopted, such as the epitaxial thin film research, and it is the aim to further develop the field by adopting other interesting research fields. We hope that you will enjoy the presentations and will also take the opportunity to attend the conference reception and banquet. On behalf of the international advisory board, the national organizing committee, the local organizing committee, and the many volunteers —Welcome to the University of Twente, Enschede.
    [Show full text]
  • MSE 422 – Electrical Ceramics Spring 2021
    MSE 422: Electrical Ceramics Spring 2021 Course Syllabus Instructor: Nicola H. Perry MSE 422 – Electrical Ceramics Spring 2021 Instructor: Prof. Nicola H. Perry Nominal Class Time: MWF 9:00-9:50AM Note: For the online version of this course, the nominal 150 minutes of in-class time per week will be split between synchronous discussions (on Zoom) and asynchronous pre-recorded lectures (on Compass). I will endeavor to not go over the allocated total time so that the online version does not end up being more work than an in-person class. This means that our Zoom discussions will not typically take up the full 9:00-9:50 AM slot. Discussions on Zoom will include: answering your questions about lecture content, summarizing the important points, presenting case studies and real-world examples of the material from lectures (e.g., news/research highlights or example questions), and student presentations. The purpose of discussions is like office hours: to help you understand and apply the lecture material and connect it to relevant applications. Email: [email protected] (however, please use discussion board for communications) Office Hours: By Zoom – during the MWF 9am slot (group office hours) or after it (individual) Course Website: Compass (https://compass2g.illinois.edu/webapps/login/) Lectures: Posted on Compass (asynchronous – watch when it’s convenient for you) Study Guides: Posted on Compass Extra Readings: Posted on Compass Presentation Guide: Posted on Compass Calendar: Posted on Compass Syllabus: Posted on Compass Other Platforms: Links will be provided through the Compass site for every other platform we use for class meetings, assignments, discussion boards, etc.
    [Show full text]
  • University of Cincinnati
    UNIVERSITY OF CINCINNATI Date:___________________ I, _________________________________________________________, hereby submit this work as part of the requirements for the degree of: in: It is entitled: This work and its defense approved by: Chair: _______________________________ _______________________________ _______________________________ _______________________________ _______________________________ High Strain Functionally Graded Barium Titanate and its Mathematical Characterization A dissertation submitted to the Division of Research and Advanced Studies of the University of Cincinnati In partial fulfillment of the requirements for the degree of Masters of Science In the Department of Chemical and Materials Engineering of the College of Engineering 27th September, 2004 By Rajesh Surana B.E., Govt. College of Engineering, Pune, 2000 Committee Chair: Dr. Relva C. Buchanan. Abstract: Ferroelectric materials are used in variety of sensor and actuator applications These are generally piezoelectric or electrostrictive, polycrystalline ceramics. The behavior of conventional materials is characterized by good high frequency response and low hysteresis, though the strains are limited to 0.1 %. A variety of methods have been developed for creating large displacement actuators by using monomorph or bimorph benders, RAINBOW, single crystals, relaxor based systems such as PMN-PT, formulated near the morphotropic phase boundary etc. In unimorphs and bimorphs; the bonding interface has low strength. Also large stress discontinuity and concentration
    [Show full text]
  • Barium Titanate and Barium Strontium Titanate Thin Films Were Deposited on Base Metal Foils Via Chemical Solution Deposition and Radio Frequency Magnetron Sputtering
    ABSTRACT AYGÜN, SEYMEN MURAT. Processing Science of Barium Titanate. (Under the direction of Jon-Paul Maria.) Barium titanate and barium strontium titanate thin films were deposited on base metal foils via chemical solution deposition and radio frequency magnetron sputtering. The films were processed at elevated temperatures for densification and crystallization. Two unifying research goals underpin all experiments: 1) To improve our fundamental understanding of complex oxide processing science, and 2) to translate those improvements into materials with superior structural and electrical properties. The relationships linking dielectric response, grain size, and thermal budget for sputtered barium strontium titanate were illustrated. (Ba0.6Sr0.4)TiO3 films were sputtered on nickel foils at temperatures ranging between 100-400 °C. After the top electrode deposition, the films were co-fired at 900 °C for densification and crystallization. The dielectric properties were observed to improve with increasing sputter temperature reaching a permittivity of 1800, a tunability of 10:1, and a loss tangent of less than 0.015 for the sample sputtered at 400 °C. The data can be understood using a brick wall model incorporating a high permittivity grain interior with low permittivity grain boundary. However, this high permittivity value was achieved at a grain size of 80 nm, which is typically associated with strong suppression of the dielectric response. These results clearly show that conventional models that parameterize permittivity with crystal diameter or film thickness alone are insufficiently sophisticated. Better models are needed that incorporate the influence of microstructure and crystal structure. This thesis next explores the ability to tune microstructure and properties of chemically solution deposited BaTiO3 thin films by modulation of heat treatment thermal profiles and firing atmosphere composition.
    [Show full text]
  • Studies of Pure and Doped Lead Zirconate Titanate Ceramics and Pulsed Laser Deposited Lead Zirconate Titanate Thin Films
    STUDIES OF PURE AND DOPED LEAD ZIRCONATE TITANATE CERAMICS AND PULSED LASER DEPOSITED LEAD ZIRCONATE TITANATE THIN FILMS A THESIS REPORT Submitted by M. PRABU Under the guidance of Dr. I. B. SHAMEEM BANU in partial fulfillment for the award of the degree of DOCTOR OF PHILOSOPHY in DEPARTMENT OF PHYSICS B.S.ABDUR RAHMAN UNIVERSITY (B.S. ABDUR RAHMAN INSTITUTE OF SCIENCE & TECHNOLOGY) (Estd. u/s 3 of the UGC Act. 1956) www.bsauniv.ac.in FEBRUARY 2013 i ii iii B.S.ABDUR RAHMAN UNIVERSITY (B.S. ABDUR RAHMAN INSTITUTE OF SCIENCE & TECHNOLOGY) (Estd. u/s 3 of the UGC Act. 1956) www.bsauniv.ac.in BONAFIDE CERTIFICATE Certified that this thesis report STUDIES OF PURE AND DOPED LEAD ZIRCONATE TITANATE CERAMICS AND PULSED LASER DEPOSITED LEAD ZIRCONATE TITANATE THIN FILMS is the bonafide work of PRABU. M (RRN: 0990202) who carried out the thesis work under my supervision. Certified further, that to the best of my knowledge the work reported herein does not form part of any other thesis report or dissertation on the basis of which a degree or award was conferred on an earlier occasion on this or any other candidate. SIGNATURE SIGNATURE Dr. I. B. SHAMEEM BANU Dr. M. BHASHEER AHMED RESEARCH SUPERVISOR HEAD OF THE DEPARTMENT Professor & Dean (SPCS) Professor & Head Department of Physics Department of Physics B. S. Abdur Rahman University B. S. Abdur Rahman University Vandalur, Chennai – 600 048 Vandalur, Chennai – 600 048 iv ABSTRACT The thesis presents the studies of pure and doped lead zirconate titanate ceramics and pulsed laser deposited lead zirconate titanate thin films.
    [Show full text]
  • I Ceramic Material Classes
    I Ceramic Material Classes Ceramics Science and Technology Volume 2: Properties. Edited by Ralf Riedel and I-Wei Chen Copyright Ó 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim ISBN: 978-3-527-31156-9 j3 1 Ceramic Oxides Dušan Galusek and Katarína Ghillanyova 1.1 Introduction Ceramic oxides represent the most extensive group of ceramic materials produced today. Traditionally, but rather artificially, the oxide ceramics are divided into traditional and advanced groups. The traditional ceramics include mostly silica-based products prepared from natural raw materials (clays), including building parts (bricks, tiles), pottery, sanitary ware, and porcelain, but also ceramics with other main components (e.g., alumina, magnesia), which are applied in the field of electroceramics (insulators), or industrial refractories. Advanced ceramics require a much higher quality and purity of raw materials, as well as the careful control of processing conditions and of the materials micro- structure. They usually comprise oxides, which do not quite fall within the traditional understanding of the term silicate materials and ceramics. Oxides found in these ceramics include mostly oxides of metals such as aluminum, zirconium, titanium, and rare earth elements. Originally investigated mainly as materials for structural applications (especially alumina and zirconia), ceramic materials (and not only oxides) partly failed to meet the expectations, mainly due to problems with reliability and high production costs. In recent years, therefore, a significant shift has been observed in pursuing and utilizing the functional properties of ceramic materials, especially chemical (high inertness), optical, electrical, and magnetic properties. Another area of research which has been pursued in recent years is the refinement of microstructure to the nanolevel.
    [Show full text]
  • (PZT) Piezoelectric Ceramics Ching-Chang Chung University of Connecticut - Storrs, [email protected]
    University of Connecticut OpenCommons@UConn Doctoral Dissertations University of Connecticut Graduate School 1-13-2014 Microstructural Evolution in Lead Zirconate Titanate (PZT) Piezoelectric Ceramics Ching-Chang Chung University of Connecticut - Storrs, [email protected] Follow this and additional works at: https://opencommons.uconn.edu/dissertations Recommended Citation Chung, Ching-Chang, "Microstructural Evolution in Lead Zirconate Titanate (PZT) Piezoelectric Ceramics" (2014). Doctoral Dissertations. 293. https://opencommons.uconn.edu/dissertations/293 Microstructural Evolution in Lead Zirconate Titanate (PZT) Piezoelectric Ceramics Ching-Chang Chung, Ph.D. University of Connecticut, 2014 Solid solutions of lead zirconate titanate [PbZr1-xTixO3 (PZT)] are extensively used in electromechanical transducers. A maximum in dielectric and piezoelectric response is observed near the morphotropic phase boundary (MPB) separating rhombohedral and tetragonal ferroelectric phases. The origin of the enhanced properties near the MPB remains controversial and has been variously attributed to coexisting rhombohedral and tetragonal ferroelectric phases, to the formation of nanodomains, and/or to lower symmetry monoclinic phases. Hence, the phase diagram of PZT in the region of the MPB remains open to debate. In this work, dense polycrystalline PZT ceramics prepared by chemical methods were subjected to different time-temperature histories to investigate the origins of the two-phase coexistence and to determine the influence of thermal history on structure, microstructure and dielectric properties. Long annealing (240 hours) above the Curie temperature (Tc) revealed a slow relaxation process that was manifested in changes of structural properties. The changes in structural properties were accompanied by changes in the behavior of the paraelectric to ferroelectric phase transition, the domain structure, and the extrinsic contributions to dielectric permittivity.
    [Show full text]
  • Phase Transitions in Sn-Modified Lead Zirconate Titanate Antiferroelectric Ceramics Hui He Iowa State University
    Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 2007 Phase transitions in Sn-modified lead zirconate titanate antiferroelectric ceramics Hui He Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Condensed Matter Physics Commons, and the Materials Science and Engineering Commons Recommended Citation He, Hui, "Phase transitions in Sn-modified lead zirconate titanate antiferroelectric ceramics" (2007). Retrospective Theses and Dissertations. 15923. https://lib.dr.iastate.edu/rtd/15923 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Phase transitions in Sn-modified lead zirconate titanate antiferroelectric ceramics by Hui He A dissertation submitted to the graduate faculty in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Major: Materials Science and Engineering Program of Study Committee: Xiaoli Tan, Major Professor Ashraf F. Bastawros Matthew J. Kramer R. William McCallum Joerg Schmalian Iowa State University Ames, Iowa 2007 Copyright © Hui He, 2007. All rights reserved. UMI Number: 3274865 Copyright 2007 by He, Hui All rights reserved. UMI Microform 3274865 Copyright 2007 by ProQuest Information and Learning Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. ProQuest Information and Learning Company 300 North Zeeb Road P.O. Box 1346 Ann Arbor, MI 48106-1346 ii Dedicated to my parents and Hang Yan for their love and support during my education iii Table of Contents Abstract …………………………………………...…………………………………….vi 1.
    [Show full text]
  • 1. Introduction Barium Titanate (Batio3) Has Been of Practical
    1. Introduction Barium titanate (BaTiO3) has been of practical interest for more than 60 years because of its attractive properties. Firstly, because it is chemically and mechanically very stable, secondly, because it exhibits ferroelectric properties at and above room temperature, and finally because it can be easily prepared and used in the form of ceramic polycrystalline samples [1]. Due to its high dielectric constant and low loss characteristics, barium titanate has been used in applications. The properties of BaTiO3 have been reported in a number of papers. Barium titanate is a member of a large group of compounds which is called the perovskite family. Ceramic materials with a perovskite structure are very significant electronic materials. 1.1. Ferroelectric materials in general The phenomenon of ferroelectricity was discovered in single-crystal materials of Rochelle salt (sodium tartarate tetrahydrate, NaKC4H4O6 · 4H2O) in 1921. The two conditions necessary in a material to classify it as a ferroelectric are (1) the existence of spontaneous polarization and (2) a demonstrated reorienting of the polarization [2]. Spontaneously polarized regions, with a single direction of polarization, are called domains. Orientation relationships between domains are governed by the crystal symmetry. The most outstanding feature of a ferroelectric ceramic is its hysteresis loop (i.e. a plot of polarization versus electric field, P-E). Fig.1.1 illustrates a typical hysteresis loop. 1 Fig.1.1. A typical P-E hysteresis loop in ferroelectrics [3] When we apply an electric field, dipoles which are already oriented in the direction of the field will remain so aligned, but those which are oriented in the opposite direction will show a tendency to reverse their orientation, on the hysteresis loop that is a linear relationship between P and E and crystal behaves like a normal dielectric.
    [Show full text]