Ishihara T. (Ed.) Perovskite Oxide for Solid Oxide Fuel Cells (Fuel Cells and Hydrogen Energy)
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Perovskite Oxide for Solid Oxide Fuel Cells
FUEL CELLS AND HYDROGEN ENERGY
Series Editor:
Narottam P. Bansal
NASA Glenn Research Center
Cleveland, OH 44135
narottam.p.bansal@nasa.gov
Aims and Scope of the Series
During the plast couple of decades, notable developments have taken place in
the science and technology of fuel cells and hydrogen energy. Most of the
knowledge developed in this field is contained in individual journal articles,
conference proceedings, research reports, etc. Our goal in developing this series
is to organize this information and make it easily availab le to scientists, engi-
neers, technol ogists, designers, technical managers, and graduate students. The
book series is focused to ensure that those who are interested in this subject can
find the information quickly and easily without having to search through the
whole literature. The series includes all aspects of the materials, science, engi-
neering, manufacturing, modeling, and applications. Fuel reforming and pro-
cessing; sensors for hydrogen, hydrocarbons, and other gases will also be
covered within the scope of this series. A number of volumes edited/authored
by internationally respected researchers from various countries are planned for
publication during the next few years.
Titles in this series
Perovskite Oxide for Solid Oxide Fuel Cells
T. Ishihara, ed.
ISBN 978-0-387-77707-8, 2009
Nanomaterials for Solid State Hydrogen Storage
R.A. Varin, T. Czujko, and Z. S. Wronski
ISBN 978-0-387-77711-5, 2009
Modeling Solid Oxide Fuel Cells: Methods, Procedures and Tech niques
R. Bove and S. Ubertini, eds.
ISBN 978-1-4020-6994-9, 2008
Tatsumi Ishihara
Editor
Perovskite Oxide for Solid
Oxide Fuel Cells
13
Editor
Tatsumi Ishihara
Faculty of Engineering
Department of Applied Chemistry
Kyushu University
744 Motooka
Nishi-ku, Fukuoka
819-0395 JAPAN
ishihara@cstf.kyushu-u.ac.jp
ISBN 978-0-387-77707-8 e-ISBN 978-0-387-77708-5
DOI 10.1007/978-0-387-77708-5
Springer Dordrecht Heidelberg London New York
Library of Congress Control Number: 2008936301
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Preface
Fuel cell technology is quite promising for conversion of chemical energy of
hydrocarbon fuels into electricity without forming air pollutants. Ther e are
several types of fuel cells: polymer electrolyte fuel cell (PEFC), phosphoric acid
fuel cell (PAFC), molten carbonate fuel cell (MCFC), solid oxide fuel cell
(SOFC), and alkaline fuel cell (AFC). Among these, SOFCs are the most
efficient and have various advantages such as flexibility in fuel, high
reliability, simple balance of plant (BOP), and a long history. Therefore,
SOFC technology is attracting much attention as a power plant and is now
close to marketing as a combined heat and power generation system. From the
beginning of SOFC development, many perovskite oxides have been used for
SOFC components; for example, LaMnO
3
-based oxide for the cathode and
LaCrO
3
for the interconnect are the most well known materials for SOFCs. The
current SOFCs operate at temperatures higher than 1073 K. Howe ver, lowering
the operating temperature of SOFC s is an important goal for further SOFC
development. Reliability, durability, and stability of the SOFCs could be
greatly improved by decreasing their operating temperature. In addition, a
lower operating temperature is also beneficial for shortening the startup time
and decreasing energy loss from heat radiation. For this purpose, faster oxide
ion conductors are required to replace the conventional Y
2
O
3
-stabilized ZrO
2
electrolyte. A new class of electrolytes such as LaGaO
3
is considered to be
highly useful for intermediate-temperature SOFCs.
Although a number of books on fuel cells have been published, a book
focused on the materials aspects of SOFCs is not yet available. This book
provides comprehensive and up-to-date information on the properties and
performance of perovskite oxides for SOFCs. Individual chapters have been
written by internationally renown ed researchers in their respective fields. The
book is primarily intended for use by researchers, engineers, managers, and
other technical people working in the field of SOFCs. Also, the information
contained in most of the chapters is fundamental enough for the book to be
useful even as a text for a SOFC technology course at the graduate level. I hope
that this book is able to contribute to the development of SOFCs from the
material aspects. At present, global war ming and the energy crisis are the most
v
serious problems for sustained development of human society. I belie ve that
SOFC technology would contribute in solving these issues.
I am grateful to Dr. Narottam Bansal, NASA Glenn Research Center, for
the opportunity to edit this book and for proofreading the text. The support of
Dr. Taner Akbay, Mitsubishi Materials Co. Ltd., in improving the quality of
each chapter is also highly appreciated. Finally, I thank all the authors for their
kind cooperation in spit e of their busy schedules.
Fukuoka, Japan Tatsumi Ishihara
August 2008
vi Preface
Contents
1 Structure and Properties of Perovskite Oxides.................. 1
Tatsumi Ishihara
1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Structure of Perovskite Oxides . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3 Typical Properties of Perovskite Oxides. . . . . . . . . . . . . . . . . . 7
1.4 Preparation of Perovskite Oxide . . . . . . . . . . . . . . . . . . . . . . . 12
1.5 Perovskite Oxides for Solid Oxide Fuel Cells (SOFCs) . . . . . . 15
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2 Overview of Intermediate-Temperature Solid Oxide Fuel Cells ..... 17
Harumi Yokokawa
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.2 Characteristic Features of Solid Oxide Fuel Cells . . . . . . . . . . 18
2.2.1 Merits and Demerits of SOFCs . . . . . . . . . . . . . . . . . . . 18
2.2.2 Issues for Intermediate-Temperature SOFCs . . . . . . . . 20
2.2.3 Stack Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
2.3 Development of Intermediate Temperature SOFC Stacks/
Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
2.3.1 Kyocera/Osaka Gas. . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
2.3.2 Mitsubishi Materials Corporation . . . . . . . . . . . . . . . . 37
2.3.3 Micro SOFCs by TOTO . . . . . . . . . . . . . . . . . . . . . . . . 38
2.4 Perspective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
2.4.1 Applications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
2.4.2 Fuel Flexibility and Reliability in Relationship
to Intermediate-Temperature SOFCs . . . . . . . . . . . . . . 41
2.4.3 Hybrid Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
2.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
3 Ionic Conduction in Perovskite-Type Compounds ............... 45
Hiroyasu Iwahara
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
3.2 Conduction Behavior of Perovskite-Type Compounds . . . . . . 46
vii
3.3 Early Studies on Ionic Conduction in Perovskite-Type
Oxides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
3.4 Oxide Ion Conduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
3.5 Proton Conduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
3.6 Lithium Ion Conduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
3.7 Halide Ion Conduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
3.8 Silver Ion Conduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
4 Oxide Ion Conductivity in Perovskite Oxide for SOFC
Electrolyte ............................................. 65
Tatsumi Ishihara
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
4.2 Oxide Ion Conductivity in Oxi de . . . . . . . . . . . . . . . . . . . . . . . 66
4.3 Oxide Ion Conductivity in Per ovskite Oxides . . . . . . . . . . . . . 68
4.4 LaGaO
3
-Based Oxide Doped with Sr and Mg (LSGM)
as a New Oxide Ion Conductor . . . . . . . . . . . . . . . . . . . . . . . . 71
4.4.1 Effects of Dopant for La and Ga Site . . . . . . . . . . . . . . 71
4.4.2 Transition Metal Doping Effects on Oxide Ion
Conductivity in LSGM . . . . . . . . . . . . . . . . . . . . . . . . . 74
4.5 Basic Properties of the LSGM Electrolyte System. . . . . . . . . . 77
4.5.1 Phase Diagram of La-Sr-Ga-Mg-O. . . . . . . . . . . . . . . . 77
4.5.2 Reactivity with SOFC Component . . . . . . . . . . . . . . . . 77
4.5.3 Thermal Expansion Behavior and Other Properties . . . 78
4.5.4 Behavior of Minor Carrier . . . . . . . . . . . . . . . . . . . . . . 79
4.5.5 Diffusivity of Oxide Ion . . . . . . . . . . . . . . . . . . . . . . . . 82
4.6 Performance of a Single Cell Using LSGM Electrolyte . . . . . . 84
4.7 Preparation of LaGaO
3
Thin-Film Electrolytes
for Application at Tem peratures Lower Than 773 K . . . . . . . 87
4.8 Oxide Ion Conductivity in the Perovskite-Related
Oxides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
4.9 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
5 Diffusivity of the Oxide Ion in Perovskite Oxides ............... 95
J. A. Kilner, A. Berenov, and J. Rossiny
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
5.1.1 Definitions of Diffusion Coefficients . . . . . . . . . . . . . . 96
5.1.2 The Oxygen Tracer Diffusion Coefficient . . . . . . . . . . . 96
5.1.3 The Surface Exchange Coefficient. . . . . . . . . . . . . . . . . 98
5.1.4 Defect Chemistry and Oxygen Transport . . . . . . . . . . . 99
5.1.5 Defect Equilibria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
5.2 Diffusion in Mixed Electronic-Ionic Conducting Oxides
(MEICs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
5.2.1 Effect of A-Site Cation on Oxygen Diffusivity . . . . . . . 103
viii Contents
5.2.2 The Effect of B-Sit e Cation on Oxygen Diffusivity. . . . 104
5.2.3 The Effect of A-Site Cation Vacancies on Oxygen
Diffusivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
5.2.4 Temperature Dependence of the Oxygen Diffusion
Coefficient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
5.2.5 The Effect of Oxygen Pressure . . . . . . . . . . . . . . . . . . . 108
5.3 Oxygen Diffusion in Ionic Conducting Perovskites . . . . . . . . . 108
5.4 Oxygen Diffusion in Perovskite-Related Materials . . . . . . . . . 110
5.5 Correlations Between Oxygen Diffusion Parameters. . . . . . . . 110
5.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
6 Structural Disorder, Diffusion Pathway of Mobile Oxide Ions,
and Crystal Structure in Perovski te-Type Oxides and Related
Materials .............................................. 117
Masatomo Yashima
6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
6.2 High-Temperature Neutron Powder Diffractometry. . . . . . . . 118
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) . . . . . . . . . . . . . . . . . 120
6.4 Diffusion Path of Oxide Ions in the Fast Oxide Ion
Conductor (La
0.8
Sr
0.2
)(Ga
0.8
Mg
0.15
Co
0.05
)O
2.8
[10] . . . . . . . . . 121
6.4.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
6.4.2 Experiments and Data Processing. . . . . . . . . . . . . . . . . 121
6.4.3 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . 122
6.5 Diffusion Path of Oxide Ions in an Oxide Ion Conductor,
La
0.64
(Ti
0.92
Nb
0.08
)O
2.99
, with a Double Perovskite-Type
Structure [11] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
6.5.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
6.5.2 Experiments and Data Processing. . . . . . . . . . . . . . . . . 126
6.5.3 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . 127
6.6 Crystal Structure and Structural Disorder of Oxide Ions
in Cathode Materials, La
0.6
Sr
0.4
CoO
3–
and
La
0.6
Sr
0.4
Co
0.8
Fe
0.2
O
3–
, with a Cubic Perovskite-Type
Structure [12, 13] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
6.6.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
6.6.2 Experiments and Data Processing. . . . . . . . . . . . . . . . . 131
6.6.3 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . 132
6.7 Structural Disorder and Diffusion Path of Oxide Ions in a
Doped Pr
2
NiO
4
-Based Mixed Ionic-Electronic Conductor
(Pr
0.9
La
0.1
)
2
(Ni
0.74
Cu
0.21
Ga
0.05
)O
4+
with a K
2
NiF
4
-Type
Structure [15] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
6.7.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
Contents ix