Impedance Spectroscopy and NMR Studies of Fast Ion Conducting Chalcogenide Glasses Hitendra Kumar Patel Iowa State University
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Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1993 Impedance spectroscopy and NMR studies of fast ion conducting chalcogenide glasses Hitendra Kumar Patel 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 Patel, Hitendra Kumar, "Impedance spectroscopy and NMR studies of fast ion conducting chalcogenide glasses " (1993). Retrospective Theses and Dissertations. 10850. https://lib.dr.iastate.edu/rtd/10850 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]. 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Ann Arbor, MI 48106 Impedance spectroscopy and NMR studies of fast ion conducting chalcogenide glasses by Hitendra Kumar Patel A Dissertation Submitted to the Graduate Faculty in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY Department: Materials Science and Engineering Major: Ceramic Engineering Approved: Members of the Committee: Signature was redacted for privacy. In Charge of Major Work Signature was redacted for privacy. Signature was redacted for privacy. For The K^or Department Signature was redacted for privacy. For tKe Graduate College Iowa State University Ames, Iowa 1993 Copyright © Hitendra K. Patel, 1993. All rights reserved. 11 TABLE OF CONTENTS CHAPTER 1. INTRODUCTION 1 1.1. Objective of the Dissertation 5 1.2. Outline of the Dissertation 6 CHAPTER 2. BACKGROUND 9 2.1. d.c. Conductivity (a^J 9 2.1.1. Anderson-Stuart (AS) Model 12 2.2.2. Weak Electrolyte Theory 14 2.2. a.c. Conductivity 17 2.2.1. Almond-West (AW) formalism 17 2.2.2. Conductivity relaxation 23 2.2.3. Compositional Contributions To Non-Exponentiality 32 2.3. Far-IR and IR Absorption 36 2.4. Nuclear Spin Lattice Relaxation (NSLR) 37 2.5. Relationships Between Nuclear Magnetic Resonance and Ionic Conductivity 42 2.6. Selection of Fast Ion Conducting Glass Systems 51 2.7. Proposed Plan of Study 53 CHAPTERS. EXPERIMENTAL METHODS 56 3.1. Low Frequency (1 Hz -1 MHz) Impedance Spectroscopy Workstation 56 3.1.1. Problems In The Original Design 58 3.1.2. Conductivity Cell Improvements 62 3.1.3. Characterization of the Optimized Conductivity Cell 63 Ill 3.2. High Frequency (1 MHz -1 GHz) Impedance Spectroscopy Workstation 69 3.2.1. Principles of Reflectance Measurements 70 3.2.2. Instrumentation Hardware 82 3.2.3. Conductivity Cell Design and Setup 92 3.2.4. Temperature Characterization and Control 105 3.2.5. Automation Software 113 3.2.6. Data Analysis Software 118 3.2.7. Workstation Performance 121 3.3. NSLR Measurements 132 3.4. Glass Preparation 134 3.3.1. B^S] Glasses 134 3.3.2. MjS + BjSj Glasses 141 3.3.3. MjS + SiSj Glasses 142 3.3.4. Sample Preparation 142 CHAPTER 4: CONDUCTIVITY RESULTS 145 4.1. Summary of Results 145 4.2. Conductivity Parameters 149 4.2.1. d.c. Conductivity Parameters 149 4.2.2. Dielectric Parameters 154 4.2.3. Almond-West Model Parameters 160 4.3.2. Electrical Modulus and KWW relaxation fiinction (P) 166 CHAPTER 5; COMPOSITIONAL CONTRIBUTION TO THE CONDUCTIVITY 172 5.1. MjS + B2S3 Glasses 173 5.1.1. d.c. Conductivity 174 5.1.2. Conductivity Relaxation 193 5.1.3. Conclusions 214 I iv CHAPTER 6: RELATIONS BETWEEN NSLR AND CONDUCTIVITY 217 6.1. NSLR (4 MHz - 40 MHz) Results 219 6.2. High Frequency (I Hz- 200 MHz) Conductivity Results 226 6.3. Results 236 6.4. Relations between NSLR and Conductivity 237 6.4.1. Activation Energies For The Two Processes 237 6.4.2. Correlation Functions 237 6.5. Conclusions 245 CHAPTER 7: ELECTRICAL MODULUS FORMALISM 248 7.1. Fundamentals of the Electrical modulus Formalism 250 7.1.1. Existence of a M" Peak For Constant a and e' 259 7.1.2. Relationship Between M" Peak Frequency and Ion-Hopping Frequency 260 7.1.3. Frequency Dependence of M" at High Frequencies 260 7.1.4. Compositional Contribution to Non-Exponentiality 261 7.1.5. Reasons For The Failure Of The KWW Function 268 7.2. Conclusions 273 CHAPTER 8: CONCLUSIONS 276 BIBLIOGRAPHY 278 ACKNOWLEDGMENTS 287 APPENDIX A. AutoCad DRAWINGS 289 APPENDIX B. SOFTWARE ALGORITHMS 294 1 CHAPTER 1. INTRODUCTION The discovery of fast ion conduction in oxide glasses by Otto in 1960 [I] and the energy crisis of the eariy 1970s stimulated much interest in using glasses as solid state electrolytes in advanced battery systems. A considerable research effort led to the synthesis of glasses with room temperature d.c. conductivities as high as 10'^ (Qcm)''. Much of the success in choos ing the chemical compositions, leading to glasses with high d.c. conductivities, may be attrib uted to the predictive nature of the Anderson-Stuart (structural) model [2] and the Ravine-Souquet weak electrolyte (thermodynamic) model [3]. The microscopic mechanisms responsible for ion conduction in glass, however, are still not well understood due to the diffi culty in independently determining the carrier concentration and mobility. Further compari sons of experimental data to predictions of the d.c. conductivity models are necessary before either model is widely accepted, modified or even replaced by newer models. Less attention has been given to understanding the a.c. conductivity, a(a}), although most d.c. conductivity data are obtained from a complex plane analysis of frequency depend ent impedance measurements. The frequency dependence of the real part of the complex conducti\dty for ion conducting glasses is similar to that observed for most disordered materi als and exhibits the "universal dielectric response", first reported by Jonscher [4,5]. This spectrum, shown in Figure 1.1, exhibits three features: (1) a frequency independent conduc tivity ("d.c. plateau") observed at low frequencies and/or highest temperatures, (2) an in crease in conductivity at higher frequencies and/or lower temperatures, and (3) a temperature independent resonant absorption peak at very high frequencies (Far-IR). The three regions are briefly described below and the conductivity mechanisms thought to be operating in each region are described in more detail in the next chapter. 2 1 iii| 1 nil 1 iii{ 1 nil 1 iii| 1 nil 1 III 1 nil 1 iiij 1 nil 11 ii{ 1 nil 1 iii| 1 m 10 Audio Radio Micro FIR IR -2 10 =- a T Inc. o — H ^ ^ "O0 o oo o -4 = I 10 a - - - - > -6 10 Slope = 1 a oooooaooo / -8 : y 10 ;5cxxxxxxxx^^++ .;++++++++" y 1 ml 1 nil i/iil 1 nil 1 ml m 1 nil 1 ml Mill 1 1 il 1 mi 1 III! 1 ITT 10 11ll 10 12 14 10 10 10 10 10 10 10 10 Frequency (Hz) Figure 1.1: Universal frequency response of conductivity in all disordered materials. Fea tures defined in the three regions are (1) frequency independent conductivity ("d.c. plateau") observed at low frequencies an^or highest temperatures, (2) an increase in conductivity at higher frequencies and/or lower temperatures, and (3) a temperature independent resonant absorption peak at very high (Far-IR) The value of the conductivity in the frequency independent region is defined as the ionic conductivity. Values for the d.c. conductivity from wide temperature conductivity isotherms are plotted against temperature to determine the temperature dependence of the conductivity. The conductivity dispersion in region 2 is observed for all glasses. In 1957, Stevels de scribed this feature qualitatively using a random potential energy model [6]. In the eariy 1970's, Macedo et al. [7] were first to suggest that the conductivity dispersion was a conse quence of the conductivity relaxation in the time domain. They introduced the concept of the electrical modulus and modeled the conductivity dispersion/relaxation using a single relaxation 3 time exponential correlation function (Debye).