Strain Mechanisms in Lead-Free Ferroelectrics for Actuators (eBook)

Parts of this thesis have been published in the following journal articles:M. Acosta, N. Novak, G. A. Rossetti, Jr., and J. Rödel, ``Mechanisms of electromechanical response in (12212x)Ba(Zr0.2Ti0.8)O32212x(Ba0.7Ca0.3)TiO3 ceramics'', Applied Physics Letters 107, 142906 (2015).M. Acosta, L. A. Schmitt, L. Molina-Luna, M. C. Scherrer, M. Brilz, K. G. Webber, M. Deluca, H. J. Kleebe, J. Rödel, and W. Donner, ``Core-shell lead-free piezoelectric ceramics: current status and advanced characterization of the Bi1/2Na1/2TiO3-SrTiO3 system'', Journal of the American Ceramic Society, 98, 3405 (2015).M. Acosta, N. Khakpash, T. Someya, N. Novak, W. Jo, H. Nagata, G. A. Rossetti, Jr., and J. Rödel, ``Origin of the large piezoelectric activity in (1-x)Ba(Zr0.2Ti0.8)O3-x(Ba0.7Ca0.3)TiO3 ceramics'', Physical Review B 91, 104108 (2015).M. Acosta, N. Novak, W. Jo, and J. Rödel, ``Relationship between electromechanical properties and phase diagram in the (1-x)Ba(Zr0.2Ti0.8)O3-x(Ba0.7Ca0.3)TiO3 lead-free piezoceramic'', Acta Materialia 80, 48 (2014).M. Acosta, W. Jo, and J. Rödel, ``Temperature- and Frequency-Dependent Properties of the 0.75Bi1/2Na1/2TiO3-0.25SrTiO3 Lead-Free Incipient Piezoceramic'', Journal of the American Ceramic Society 97, 1937 (2014).W. Jo, R. Dittmer, M. Acosta, J. Zang, C. Groh, E. Sapper, K. Wang, and J. Rödel, ``Giant electric-field-induced strains in lead-free ceramics for actuator applications-status and perspective'', Journal of Electroceramics 29, 71 (2012). 6
Supervisor's Foreword 8
Acknowledgments 10
Contents 13
Abbreviations 15
1 Introduction 17
Bibliography 20
2 Theoretical Background 22
2.1 Dielectrics 22
2.2 Classification of Dielectrics 25
2.2.1 Ferroelectrics 29
2.2.2 Relaxor Ferroelectrics 35
2.2.2.1 General Description 35
2.2.2.2 Lead-Free Relaxor Ferroelectrics 40
2.3 Electromechanical Enhancements in Ferroelectrics 42
2.3.1 Composition Engineering 43
2.3.1.1 Phase Instabilities 43
2.3.1.2 Doping 47
2.3.2 Structure Engineering 48
2.3.2.1 Grain and Domain Engineering 48
2.3.2.2 Texturing 49
2.3.2.3 Design of Heterogeneous Materials 50
Bibliography 52
3 Literature Review: Piezoceramics for Actuator Applications 58
3.1 The (1 2212 x)Ba(Zr0.2Ti0.8)O3--x(Ba0.7Ca0.3)TiO3 System 61
3.1.1 Processing 61
3.1.2 Atomic Structure 62
3.1.3 Microstructure 64
3.1.4 Electromechanical Properties 66
3.2 The (1 2212 x)(Bi1/2Na1/2)TiO3--xSrTiO3 System 68
3.2.1 Processing 68
3.2.2 Atomic Structure 70
3.2.3 Microstructure 72
3.2.4 Electromechanical Properties 72
Bibliography 74
4 Experimental Procedure 79
4.1 Powder and Ceramic Processing 79
4.2 Structural Characterization 81
4.2.1 Atomic Characterization 81
4.2.1.1 X-Ray Diffraction 81
4.2.1.2 Neutron Diffraction 82
4.2.2 Microstructural Characterization 83
4.2.2.1 Scanning and Transmission Electron Microscopy 83
4.2.2.2 Density 84
4.3 Thermal Analysis 84
4.4 Electrical Characterization 85
4.4.1 Temperature- and Frequency-Dependent Dielectric Properties 85
4.4.2 Small Signal Properties 86
4.4.2.1 Temperature-Dependent Quasi-Static Characterization 86
4.4.2.2 Electric Field- and Temperature-Dependent Quasi-Static Characterization 86
4.4.2.3 Dynamic Characterization 87
4.4.3 Temperature- and Frequency-Dependent Quasi-Static Large Signal Properties 87
Bibliography 89
5 Results and Discussions 90
5.1 The (1 2212 x)Ba(Zr0.2Ti0.8)O3--x(Ba0.7Ca0.3)TiO3 System 90
5.1.1 Atomic Characterization 90
5.1.2 Microstructure Characterization 92
5.1.3 Electrical Characterization 94
5.1.3.1 Temperature- and Frequency-Dependent Dielectric Properties 94
5.1.3.2 Small Signal Properties 97
Temperature-Dependent Quasi-Static Small Signal Properties 97
Dynamic Properties 99
Bias-Field- and Temperature-Dependent Quasi-Static Small Signal Properties 104
5.1.3.3 Quasi-Static Large Signal Properties 111
5.1.4 Strain Mechanisms of the (1 2212 x)Ba(Zr0.2Ti0.8)O3--x(Ba0.7Ca0.3)TiO3 System 115
5.2 The (1 2212 x)(Bi1/2Na1/2)TiO3--xSrTiO3 System 124
5.2.1 Synthesis Study 124
5.2.2 Atomic Characterization 126
5.2.3 Microstructure Characterization 130
5.2.4 Electrical Characterization 135
5.2.4.1 Temperature- and Frequency-Dependent Dielectric Properties 135
5.2.4.2 Bias-Field- and Temperature-Dependent Quasi-Static Small Signal Properties 137
5.2.4.3 Quasi-Static Large Signal Properties 139
5.2.5 Effect of Microstructure on the Quasi-Static Large Signal Properties 147
5.2.6 Strain Mechanisms of the (1 2212 x)(Bi1/2Na1/2)TiO3--xSrTiO3 System 148
Bibliography 157
6 Conclusions 163
7 Remarks and Future Work 167
Bibliography 169
Appendix I Nomenclature for Core-ShellMicrostructures 170
Appendix II Electromechanical Equations 173
Appendix III Dielectric Relaxation in the (1 ? x)Ba(Zr0.2Ti0.8)O3–x(Ba0.7Ca0.3)TiO3 System 175
Appendix IV Cycling Reliability of the (1 ? x)(Bi1/2Na1/2)TiO3–xSrTiO3 System 177
Appendix V Application-Oriented Characterization 179
Summarized Curriculum Vitae 183