Perovskite Oxide for Solid Oxide Fuel Cells (eBook)

Preface 6
Contents 8
Contributors 15
Structure and Properties of Perovskite Oxides 17
1.1 Introduction 17
1.2 Structure of Perovskite Oxides 18
1.3 Typical Properties of Perovskite Oxides 23
1.4 Preparation of Perovskite Oxide 28
1.5 Perovskite Oxides for Solid Oxide Fuel Cells (SOFCs) 31
References 32
Overview of Intermediate-Temperature Solid Oxide Fuel Cells 33
2.1 Introduction 33
2.2 Characteristic Features of Solid Oxide Fuel Cells 34
2.2.1 Merits and Demerits of SOFCs 34
2.2.2 Issues for Intermediate-Temperature SOFCs 36
2.2.2.1 Electrolytes and Conversion Efficiency 37
2.2.2.2 Cathode 41
Relationship with YSZ and Cr Poisoning 41
Compatibility with LSGM 44
2.2.2.3 Anode 44
Nickel Anode 45
Nickel Anode with LSGM Electrolyte 47
Oxide Anodes 48
2.2.2.4 Metal Interconnects 48
2.2.3 Stack Design 51
2.3 Development of Intermediate Temperature SOFC Stacks/Systems 52
2.3.1 Kyocera/Osaka Gas 52
2.3.2 Mitsubishi Materials Corporation 53
2.3.3 Micro SOFCs by TOTO 54
2.4 Perspective 54
2.4.1 Applications 54
2.4.2 Fuel Flexibility and Reliability in Relationship to Intermediate-Temperature SOFCs 57
2.4.3 Hybrid Systems 57
2.5 Summary 58
References 58
Ionic Conduction in Perovskite-Type Compounds 60
3.1 Introduction 60
3.2 Conduction Behavior of Perovskite-Type Compounds 61
3.3 Early Studies on Ionic Conduction in Perovskite-Type Oxides 64
3.4 Oxide Ion Conduction 67
3.5 Proton Conduction 70
3.6 Lithium Ion Conduction 74
3.7 Halide Ion Conduction 75
3.8 Silver Ion Conduction 76
References 77
Oxide Ion Conductivity in Perovskite Oxide for SOFC Electrolyte 79
4.1 Introduction 79
4.2 Oxide Ion Conductivity in Oxide 80
4.3 Oxide Ion Conductivity in Perovskite Oxides 82
4.4 LaGaO3-Based Oxide Doped with Sr and Mg (LSGM) as a New Oxide Ion Conductor 85
4.4.1 Effects of Dopant for La and Ga Site 85
4.4.2 Transition Metal Doping Effects on Oxide Ion Conductivity in LSGM 88
4.5 Basic Properties of the LSGM Electrolyte System 91
4.5.1 Phase Diagram of La-Sr-Ga-Mg-O 91
4.5.2 Reactivity with SOFC Component 91
4.5.3 Thermal Expansion Behavior and Other Properties 92
4.5.4 Behavior of Minor Carrier 93
4.5.5 Diffusivity of Oxide Ion 96
4.6 Performance of a Single Cell Using LSGM Electrolyte 98
4.7 Preparation of LaGaO3 Thin-Film Electrolytes for Application at Temperatures Lower Than 773 K 101
4.8 Oxide Ion Conductivity in the Perovskite-Related Oxides 103
4.9 Summary 106
References 106
Diffusivity of the Oxide Ion in Perovskite Oxides 108
5.1 Introduction 108
5.1.1 Definitions of Diffusion Coefficients 109
5.1.2 The Oxygen Tracer Diffusion Coefficient 109
5.1.3 The Surface Exchange Coefficient 111
5.1.4 Defect Chemistry and Oxygen Transport 112
5.1.5 Defect Equilibria 112
5.2 Diffusion in Mixed Electronic-Ionic Conducting Oxides (MEICs) 115
5.2.1 Effect of A-Site Cation on Oxygen Diffusivity 116
5.2.2 The Effect of B-Site Cation on Oxygen Diffusivity 117
5.2.3 The Effect of A-Site Cation Vacancies on Oxygen Diffusivity 118
5.2.4 Temperature Dependence of the Oxygen Diffusion Coefficient 118
5.2.5 The Effect of Oxygen Pressure 121
5.3 Oxygen Diffusion in Ionic Conducting Perovskites 121
5.4 Oxygen Diffusion in Perovskite-Related Materials 123
5.5 Correlations Between Oxygen Diffusion Parameters 123
5.6 Conclusions 125
References 126
Structural Disorder, Diffusion Pathway of Mobile Oxide Ions, and Crystal Structure in Perovskite-Type Oxides and Related Materials 130
6.1 Introduction 130
6.2 High-Temperature Neutron Powder Diffractometry 131
6.3 Data Processing for Elucidation of the Diffusion Paths of Mobile Oxide Ions in Ionic Conductors: Rietveld Analysis, Maximum Entropy Method (MEM), and MEM-Based Pattern Fitting (MPF) 133
6.4 Diffusion Path of Oxide Ions in the Fast Oxide Ion Conductor (La0.8Sr0.2)(Ga0.8Mg0.15Co0.05)O2.8 [10] 134
6.4.1 Introduction 134
6.4.2 Experiments and Data Processing 134
6.4.3 Results and Discussion 135
6.5 Diffusion Path of Oxide Ions in an Oxide Ion Conductor, La0.64(Ti0.92Nb0.08)O2.99, with a Double Perovskite-Type Structure [11] 139
6.5.1 Introduction 139
6.5.2 Experiments and Data Processing 139
6.5.3 Results and Discussion 140
6.6 Crystal Structure and Structural Disorder of Oxide Ions in Cathode Materials, La0.6Sr0.4CoO3-delta and La0.6Sr0.4Co0.8Fe0.2O3-delta, with a Cubic Perovskite-Type Structure [12, 13] 144
6.6.1 Introduction 144
6.6.2 Experiments and Data Processing 144
6.6.3 Results and Discussion 145
6.6.3.1 Crystal Structure and Disorder of La0.6Sr0.4CoO3-delta 145
6.6.3.2 Crystal Structure and Disorder of La0.6Sr0.4Co0.8Fe0.2O3-delta 147
6.7 Structural Disorder and Diffusion Path of Oxide Ions in a Doped Pr2NiO4-Based Mixed Ionic-Electronic Conductor (Pr0.9La0.1)2(Ni0.74Cu0.21Ga0.05)O4+delta with a K2NiF4-Type Structure [15] 150
6.7.1 Introduction 150
6.7.2 Experiments and Data Processing 151
6.7.3 Results and Discussion 151
6.8 Conclusions 154
References 156
Perovskite Oxide for Cathode of SOFCs 159
7.1 Introduction 159
7.2 Properties Required for a Cathode Material 160
7.2.1 Catalytic Activity 160
7.2.2 Electronic Conductivity 161
7.2.3 Oxygen Transport (Bulk or Surface) 163
7.2.4 Chemical Stability and Compatibility 164
7.2.5 Morphological Stability 164
7.3 General Description of Cathode Reaction and Polarization 165
7.3.1 Oxygen Electrode Process 165
7.3.2 Equivalent Circuit for a Cathode-Electrolyte Interface 166
7.4 Cathode for High-Temperature SOFC: (La, Sr)MnO3 168
7.4.1 Transport Properties and Electrochemical Reaction 168
7.4.2 Chemical and Morphological Stability of LSM 170
7.5 Cathode for Intermediate-Temperature SOFC: (La, Sr)CoO3, (La, Sr)(Co, Fe)O3 172
7.5.1 General Features of Co-Based Perovskite Cathode 172
7.5.2 Electrochemical Reaction of a Model Electrode: A (La,Sr)CoO3 Dense Film 173
7.5.3 Electrochemical Response of (La, Sr)CoO3 on Zirconia with and Without Ceria Interlayer 175
7.6 Summary 176
References 177
Perovskite Oxide Anodes for SOFCs 179
8.1 Introduction 179
8.2 Anode Materials for SOFCs 180
8.3 Perovskite Chemistry 181
8.4 Doping, Nonstoichiometry, and Conductivity 182
8.5 Perovskite Anode Materials 185
8.6 A(B,B’)O3 Perovskites 189
8.7 Tungsten Bronze Anode Materials 190
8.8 Anode Materials for All-Perovskite Fuel Cells 191
8.9 Conclusions 192
References 192
Intermediate-Temperature Solid Oxide Fuel Cells Using LaGaO3 195
9.1 Introduction 195
9.2 Cell Development 196
9.2.1 Electrolyte 196
9.2.1.1 Doped Lanthanum Gallate 196
9.2.2 Anode 197
9.2.2.1 Nickel/Rare Earth Metal-Doped Ceria Cermet 197
9.2.3 Cathode 200
9.2.3.1 Strontium-Doped Samarium Cobaltite 201
9.2.3.2 Lanthanum-Doped Barium Cobaltite 201
9.3 Stack Development 202
9.4 Module Development 204
9.4.1 A 1-kW Class Single-Stack Module 204
9.4.2 A 10-kW Class Multi-Stack Module 207
9.5 System Development 208
9.6 Stack Modeling 210
References 214
Quick-Start-Up Type SOFC Using LaGaO3-Based New Electrolyte 216
10.1 Introduction 216
10.2 Micro-Tubular Cell Development 217
10.3 Rapid Thermal Cycling 222
10.4 Fuel Flexibility 222
10.5 Stack Development 225
10.6 Summary 227
References 227
Proton Conductivity in Perovskite Oxides 228
11.1 Introduction 228
11.2 Proton Conductivity in Acceptor-Doped Perovskites 230
11.2.1 Protons in Oxides 230
11.2.2 Hydration of Acceptor-Doped Perovskites 230
11.2.3 Proton Diffusion 233
11.2.4 Charge Mobility and Conductivity of Protons 235
11.2.5 Proton Conductivity in Acceptor-Doped Simple Perovskites, ABO3 236
11.2.6 Effects of Defect-Acceptor Interactions 239
11.2.7 Grain Boundaries 240
11.3 Proton Conduction in Inherently Oxygen-Deficient Perovskites 241
11.3.1 Hydration of Ordered Oxygen Deficiency 241
11.3.2 Nomenclature and Hydration of Disordered Intrinsic Oxygen Deficiency 242
11.3.3 Order-Disorder Reactions Involving Hydrated Inherently Oxygen-Deficient Perovskites (Oxyhydroxides) 243
11.4 Hydration of Undoped Perovskites 244
11.5 Proton Conductivity in Selected Classes Of Non-Perovskite Oxides and Phosphates 244
11.6 Developments of Proton-Conducting SOFCs 247
11.7 Conclusions 248
References 249
Proton Conduction in Cerium- and Zirconium-Based Perovskite Oxides 253
12.1 Introduction 253
12.2 Conductivity 255
12.3 Activation/Deactivation of Electrodes 257
12.4 Stability 258
12.5 Dopant 261
12.6 Proton Hole Mixed Conduction 265
References 268
Mechanisms of Proton Conduction in Perovskite-Type Oxides 270
13.1 Introduction 270
13.2 Proton Sites 271
13.3 Mechanisms of Proton Conduction (Undoped, Cubic Perovskites) 273
13.4 Complications (Symmetry Reduction, Doping, Mixed Site Occupancy) 277
13.5 Implications for the Development of Proton-Conducting Electrolytes for Fuel Cell Applications 279
References 280
Intermediate-Temperature SOFCs Using Proton-Conducting Perovskite 282
14.1 Introduction 282
14.2 Preparation of Fuel Cells 286
14.3 Characterization of Fuel Cells 286
14.4 Operation and Evaluation of Fuel Cells 288
14.5 Conclusion 291
References 292
LaCrO3-Based Perovskite for SOFC Interconnects 293
15.1 Introduction 293
15.2 Sintering Properties and Chemical Compatibility with the Other Components 294
15.3 Electronic Conductivity 295
15.4 Defect Chemistry and Oxygen Electrochemical Leak 297
15.5 Lattice Expansion During Reduction and Temperature Change 301
15.6 Mechanical Strength 301
15.7 Summary 302
References 303
Index 305