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. Lead zirconate titanate (PZT) monophase perovskite powder with the composition of Pb(Zr0.52Ti0.48)O3 was prepared via sol–gel route. The band gap was calculated for the samples using UV-vis diffused reflectance spectroscopy. The lanthanum doped lead zirconate titanate (PLZT) ceramics with nominal composition Pb1- xLax(Zr0.52Ti0.48)O3 (where x=0, 0.05, 0.10) were synthesized and studied to understand the effect of lanthanum substitution on the dielectric and the ferroelectric properties. The electrical properties of the prepared PLZT ceramics were investigated as a function of frequency for various temperatures using complex impedance spectroscopy (CIS). The values of activation energy of the samples were calculated from the slopes of the Arrhenius plots. The remnant polarization (Pr) and coercive electric field (Ec) were calculated from the ferroelectric hysteresis loop. Perovskite lead zirconate titanate nanostructured (PZT) thin films with Zr/Ti ratio of 52/48 were deposited on Pt/TiO2/SiO2/Si(100) substrate using pulsed laser deposition (PLD) method. For the measurement of ferroelectric property, metal/ferroelectric/metal (MFM) structure with gold as top electrode was used. The results of the ferroelectric properties of the film were illustrated. The voltage dependent Polarization vs. Electric field hysteresis measurements of PZT (52/48) pellet showed a well-defined hysteresis loop with a fairly high remnant polarization (Pr) and low coercive field (Ec). The optical properties of PZT thin film coated on SiO2/Si(100) were investigated using spectroscopic ellipsometry (SE). Spectra of ellipsometric parameters such as ψ and Δ were measured as a function of energy at room temperature. The refractive index (n), extinction coefficient (k), absorption coefficient (α) and the dielectric constants (εr and εi) of the thin film were obtained as a function of wavelength in the range from 200 nm to 900 nm and discussed. v ACKNOWLEDGEMENT First of all, I am truly grateful to my vibrant supervisor Dr. I. B. Shameem Banu, Dean (School of Science and Humanities) and Professor of Physics, B. S. Abdur Rahman University, Vandalur, Chennai who has been tremendously cooperative throughout my research. My sincere thanks to the Doctoral Committee members Dr. Sitaram Das, Scientist, Materials Science Division, Indira Gandhi Center for Atomic Research, Kalpakkam and Dr. R. Vasanthakumari, Professor, Department of Polymer Technology, B. S. Abdur Rahman University, Vandalur, Chennai for their critical comments and suggestions for my research work. I express my thanks to Dr. M. Basheer Ahamed, Professor and Head, Department of Physics, B. S. Abdur Rahman University, Vandalur, Chennai. It is my great pleasure to know Dr. M. S. Ramachandra Rao, Professor, Department of Physics, Indian Institute of Technology Madras and I am thankful to him for the utilization of the equipment in his esteemed laboratory. I am truly grateful to Dr. techn. Murthy Chavali, Professor and Head, Department of Nanotechnology, Noorul Islam University and I am thankful to him for the very useful discussions. It is my great pleasure to know Dr. A. Chandra Bose, Associate Professor and Head, Department of Physics, NIT Trichy and I am thankful to him for the utilization of the equipment in his esteemed laboratory. Let me take this opportunity to acknowledge some of my friends; R. Muthukumar, S. Prabu, K. K. Balan, T. Arun, S. Gobalakrishnan, R. Devaraj, and Dr. K. Karthikeyan for their pleasant company on different occasions. I wish to express my thanks to my juniors, all research scholars and staff members in Department of Physics. I must mention the huge encouragement I received from my family on a regular basis, which has been a constant source of energy for me. M. PRABU vi TABLE OF CONTENTS CHAPTER NO. TITLE PAGE NO. ABSTRACT v ACKNOWLEDGEMENT vi LIST OF TABLES x LIST OF FIGURES xi LIST OF SYMBOLS xv 1. INTRODUCTION 1 1.1 BACKGROUND AND MOTIVATION 1 1.2 AIM AND OBJECTIVE 2 1.3 OUTLINE OF THE THESIS 3 2. LITERATURE OVERVIEW 5 2.1 INTRODUCTION 5 2.2 LEAD ZIRCONATE TITANATE (PZT) 6 2.3 LANTHANUM DOPED LEAD ZIRCONATE TITANATE (PLZT) 9 2.4 LEAD ZIRCONATE TITANATE (PZT) THIN FILM 11 3. EXPERIMENTAL 16 3.1 SYNTHESIS OF LANTHANUM DOPED LEAD ZIRCONATE TITANATE 16 3.1.1 Materials 16 3.1.2 Methods 16 3.2 PREPARATION OF PELLET FOR ELECTRICAL CHARACTERIZATION 17 3.3 PREPARATION OF THIN FILM BY PULSED LASER DEPOSITION 17 3.4 CHARACTERIZATIONS 19 vii CHAPTER NO. TITLE PAGE NO. 4. ELECTRICAL AND OPTICAL CHARACTERIZATIONS OF LEAD ZIRCONATE TITANATE (PZT) CERAMICS 21 4.1 INTRODUCTION 21 4.2 RESULTS AND DISCUSSION 22 4.2.1 Structural and morphological studies 22 4.2.2 Optical study 25 4.2.3 Dielectric properties 27 4.2.4 Impedance analysis 28 4.2.5 DC conductivity studies 30 4.2.6 Ferroelectric properties 31 4.3 CONCLUSION 32 5. ELECTRICAL CHARACTERIZATIONS OF LANTHANUM DOPED PZT (PLZT) CERAMICS 34 5.1 INTRODUCTION 34 5.2 RESULTS AND DISCUSSION 35 5.2.1 Structural and morphological studies 35 5.2.2 Dielectric properties 39 5.2.3 Impedance analysis 43 5.2.4 DC conductivity studies 47 5.2.5 Ferroelectric properties 48 5.3 CONCLUSION 50 6. ELECTRICAL CHARACTERIZATIONS OF PZT THIN FILM PREPARED BY PULSED LASER DEPOSITION (PLD) METHOD 51 6.1 INTRODUCTION 51 6.2 RESULTS AND DISCUSSION 51 viii CHAPTER NO. TITLE PAGE NO. 6.2.1 Structural and morphological studies 51 6.2.2 Ferroelectric properties 54 6.2.3 I-V characteristic studies 56 6.3 CONCLUSION 57 7. OPTICAL STUDIES OF PULSED LASER DEPOSITED PZT THIN FILM BY SPECTROCOPIC ELLIPSOMETRY 58 7.1 INTRODUCTION 58 7.2 RESULTS AND DISCUSSION 59 7.2.1 Structural and morphological studies 59 7.2.2 Optical studies of PZT thin films 61 7.3 CONCLUSION 70 8. CONCLUSION 72 9. SCOPE FOR FURTHER WORK 76 REFERENCES 77 APPENDIX 1 (BASIC CONCEPTS) 88 APPENDIX 2 (PREPARATION TECHNIQUES) 95 APPENDIX 3 (CHARACTERIZATION TECHNIQUES) 104 TECHNICAL BIOGRAPHY 113 ix LIST OF TABLES TABLE NO. TITLE PAGE NO. 3.1 Deposition parameters for PZT (52/48) thin film prepared by pulsed laser deposition method 19 4.1 Crystallite size, lattice parameter and band gap of PZT (52/48) powders for different calcined powders 27 4.2 Remnant polarization (Pr) and saturation polarization (Ps) and coercive field (Ec) determined from the measured hysteresis loop for PZT (52/48) ceramics 32 5.1 Saturation (Ps) and remnant (Pr) polarization and coercive fields (Ec) determined from the measured hysteresis loops for every studied sample 49 6.1 Remnant (Pr) and saturation (Ps) polarization and coercive field (Ec) determined from the measured hysteresis loop for PZT (52/48) ceramics 55 7.1 Comparison of refractive index values of ceramics and thin films with the pulsed laser deposited PZT (52/48) thin film 66 7.2 Comparison of energy gap (Eg) of ceramics and thin films with the pulsed laser deposited PZT (52/48) thin film 69 x LIST OF FIGURES FIGURE NO. TITLE PAGE NO. 2.1 The crystal structure of the barium titanate, BaTiO3 6 2.2 Crystal structure of the lead zirconate titanate (PZT) perovskite (ABO3) structure 7 2.3 Various applications of ferroelectric thin films 12 3.1 Flow chart for sol-gel auto-combustion method for PLZT synthesize 17 4.1 XRD patterns of PZT powders calcined at different temperatures 23 4.2 XRD pattern of the PZT (powder) calcined at 850 °C for 3 hrs 23 4.3 TGA/DTA curve for the PZT powders synthesized by sol-gel route 24 4.4 SEM image of the PZT (a) powder and (b) pellet 25 4.5 UV-vis DRS spectra of PZT powders calcined at 850 °C and 900 °C for 3 hrs 26 4.6 (a) Dielectric constant vs. temperature, (b) Dielectric loss vs. temperature of PZT(52/48) ceramics for various frequencies (100 Hz- 1MHz). 28 4.7 (a) & (b) Complex impedance spectrum of PZT (52/48) ceramic material as a function of frequency for various temperatures. 29 4.8 Variation of imaginary part of impedance as a function of frequency for PZT (52/48) ceramics 29 4.9 Activation energy (Ea) of perovskite PZT (52/48) ceramics derived by fitting to the Arrhenius equation 30 4.10 (a) & (b) Hysteresis loop behavior of the PZT (52/48) ceramic for various applied electric fields 31 xi FIGURE NO.