Advances in Solid OxideFuel Cells and

Electronic Ceramics

Advances in Solid OxideFuel Cells and

Electronic Ceramics

A Collection of Papers Presented at the39th International Conference on

Advanced Ceramics and CompositesJanuary 25–30, 2015

Daytona Beach, Florida

EditorsNarottam P. Bansal

Mihails KusnezoffKiyoshi Shimamura

Volume EditorsJingyang WangSoshu Kirihara

Copyright © 2016 by The American Ceramic Society. All rights reserved.

Published by John Wiley & Sons, Inc., Hoboken, New Jersey.Published simultaneously in Canada.

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Preface ix

Introduction xi

SOLID OXIDE FUEL CELLS

Effects of TiO2 Addition on Microstructure and Ionic Conductivity 3of Gadolinia-Doped Ceria Solid Electrolyte

M. C. F. Dias and E. N. S. Muccillo

Effect of Specific Surface Area and Particle Size Distribution on the 13Densification of Gadolinium Doped Ceria

K. Paciejewska, A. Weber, S. Kühn, and M. Kleber

Study on Sintering and Stability Issues of BaZr0.1Ce0.7Y0.1Yb0.1O3- 21Electrolyte for SOFCs

Armin Vahid Mohammadi and Zhe Cheng

Sintering, Mechanical, Electrical and Oxidation Properties of Ceramic 31Intermetallic TiC-Ti3Al Composites from Nano-TiC Particles

Zhezhen Fu, Kanchan Mondal, and Rasit Koc

Characteristics of Protective LSM Coatings on Cr-Contained Steels 45used as Metallic Interconnectors of Intermediated Temperature Solid Oxide Fuel Cells

Chun-Liang Chang, Chang-sing Hwang, Chun-Huang Tsai, Sheng-Fu Yang,Wei-Ja Shong, Zong-Yang Jhuang-Shie, and Te-Jung Daron Huang

Electrical and Microstructural Evolutions of La0.67Sr0.33MnO3 Coated 57Ferritic Stainless Steels after Long-Term Aging at 800°C

Chien-Kuo Liu, Peng Yang, Wei-Ja Shong, Ruey-Yi Lee, and Jin-Yu Wu

v

Contents

Structural and Electrochemical Performance Stability of Perovskite– 67Fluorite Composite for High Temperature Electrochemical Devices

Sapna Gupta and Prabhakar Singh

Durability of Lanthanum Strontium Cobalt Ferrite 75((La0.60Sr0.40)0.95(Co0.20Fe0.80)O3-x) Cathodes in CO2 and H2O Containing Air

Boxun Hu, Manoj K. Mahapatra, Vinit Sharma, Rampi Ramprasad, Nguyen Minh, Scott Misture, and Prabhakar Singh

Fabrication of the Anode-Supported Solid Oxide Fuel Cell with 83Composite Cathodes and the Performance Evaluation upon Long-Term Operation

Tai-Nan Lin, Yang-Chuang Chang, Maw-Chwain Lee, and Ruey-yi Lee

Development of Microtubular Solid Oxide Fuel Cells using 93Hydrocarbon Fuels

Hirofumi Sumi, Hiroyuki Shimada, Toshiaki Yamaguchi, Koichi Hamamoto,Toshio Suzuki, and Yoshinobu Fujishiro

Highly Efficient Solid Oxide Electrolyzer and Sabatier System 105Viswanathan Venkateswaran, Tim Curry, Christie Iacomini, and John Olenick

SINGLE CRYSTALLINE MATERIALS FOR ELECTRICAL AND OPTICAL APPLICATIONS

The Effects of Excess Silicon and Carbon in SiC Source Materials on 117SiC Single Crystal Growth in Physical Vapor Transport Method

Tatsuo Fujimoto, Masashi Nakabayashi, Hiroshi Tsuge, Masakazu Katsuno,Shinya Sato, Shoji Uhsio, Komomo Tani, Hirokastu Yashiro, Hosei Hirano,and Takayuki Yano

Recent Progress of GaN Substrates Manufactured by VAS Method 129Takehiro Yoshida, Takayuki Suzuki, Toshio Kitamura, Yukio Abe, HajimeFujikura, Masatomo Shibata, and Toshiya Saito

Coilable Single Crystal Fibers of Doped-YAG for High Power 139Applications

B. Ponting, E. Gebremichael, R. Magana, and G. Maxwell

Hydrothermal Crystal Growth and Applications 151M. Prakasam, O. Viraphong, O. Cambon, and A. Largeteau

Reactive Atmospheres for Oxide Crystal Growth 157Detlef Klimm, Steffen Ganschow, Zbigniew Galazka, Rainer Bertram, DetlevSchulz, and Reinhard Uecker

vi · Advances in Solid Oxide Fuel Cells and Electronic Ceramics

Discussion on Polycrystals over Single Crystals for Optical Devices 169Mythili Prakasam and Alain Largeteau

Terahertz Time-Domain Spectroscopy Application to Non- 177Destructive Quality Evaluation of Industrial Crystalline Materials

S. Nishizawa, T. Nagashima, M. W. Takeda, and K. Shimamura

Author Index 187

Advances in Solid Oxide Fuel Cells and Electronic Ceramics · vii

The 12th International Symposium on Solid Oxide Fuel Cells (SOFC): Materials,Science, and Technology and a Focused Session: Single Crystalline Materials forElectrical, Optical and Medical Applications were held during the 39th Internation-al Conference and Exposition on Advanced Ceramics and Composites in DaytonaBeach, FL, January 25–30, 2015. These symposia provided an international forumfor scientists, engineers, and technologists to discuss and exchange state-of-the-artideas, information, and technology on various aspects of solid oxide fuel cells andsingle crystal materials for electronic applications. This CESP issue contains 18 pa-pers submitted by authors of these two symposia for inclusion in the meeting pro-ceedings.

The editors wish to extend their gratitude and appreciation to all the authors fortheir contributions and cooperation, to all the participants and session chairs fortheir time and efforts, and to all the reviewers for their useful comments and sug-gestions. Financial support from The American Ceramic Society is gratefully ac-knowledged. Thanks are due to the staff of the meetings and publications depart-ments of The American Ceramic Society for their invaluable assistance.

Advice, help and cooperation of the following members of the international or-ganizing committee at various stages were instrumental in making this symposiumand focused session a great success.

12 International Symposium on SOCFs: Vincenzo Esposito, Tatsumi Ishihara,Ruey-Yi Lee, Nguyen Minh, Mogens Mogensen, Prabhakar Singh, FedericoSmeacetto, Jeffry Stevenson, Toshio Suzuki, and Sascha Kuhn Single Crystalline Materials: Noboru Ichinose, Robert Feigelson, Richard Moncorgé, Reinhard Uecker, Alain Largeteau, Mauro Tonelli

We hope that this volume will serve as a valuable reference for the engineers,scientists, researchers and others interested in the materials, science and technologyof solid oxide fuel cells and single crystal materials.

NAROTTAM P. BANSAL

NASA Glenn Research Center, USA

ix

Preface

MIHAILS KUSNEZOFF

Fraunhofer IKTS, GERMANY

KIYOSHI SHIMAMURA

National Institute for Materials Science, JAPAN

x · Advances in Solid Oxide Fuel Cells and Electronic Ceramics

xi

Introduction

This CESP issue consists of papers that were submitted and approved for the pro-ceedings of the 39th International Conference on Advanced Ceramics and Compos-ites (ICACC), held January 25–30, 2015 in Daytona Beach, Florida. ICACC is themost prominent international meeting in the area of advanced structural, functional,and nanoscopic ceramics, composites, and other emerging ceramic materials andtechnologies. This prestigious conference has been organized by the EngineeringCeramics Division (ECD) of The American Ceramic Society (ACerS) since 1977.

The 39th ICACC hosted more than 1,000 attendees from 40 countries and over800 presentations. The topics ranged from ceramic nanomaterials to structural relia-bility of ceramic components which demonstrated the linkage between materialsscience developments at the atomic level and macro level structural applications.Papers addressed material, model, and component development and investigatedthe interrelations between the processing, properties, and microstructure of ceramicmaterials.

The 2015 conference was organized into the following 21 symposia and ses-sions:

Symposium 1 Mechanical Behavior and Performance of Ceramics and Composites

Symposium 2 Advanced Ceramic Coatings for Structural, Environmental, and Functional Applications

Symposium 3 12th International Symposium on Solid Oxide Fuel Cells (SOFC): Materials, Science, and Technology

Symposium 4 Armor Ceramics: Challenges and New DevelopmentsSymposium 5 Next Generation Bioceramics and BiocompositesSymposium 6 Advanced Materials and Technologies for Energy Generation and

Rechargeable Energy StorageSymposium 7 9th International Symposium on Nanostructured Materials and

Nanocomposites Symposium 8 9th International Symposium on Advanced Processing &

Manufacturing Technologies for Structural & Multifunctional Materials and Systems (APMT), In Honor of Prof. Stuart Hampshire

Symposium 9 Porous Ceramics: Novel Developments and ApplicationsSymposium 10 Virtual Materials (Computational) Design and Ceramic GenomeSymposium 11 Advanced Materials and Innovative Processing ideas for the

Industrial Root TechnologySymposium 12 Materials for Extreme Environments: Ultrahigh Temperature

Ceramics (UHTCs) and Nanolaminated Ternary Carbides and Nitrides (MAX Phases)

Symposium 13 Advanced Ceramics and Composites for Sustainable Nuclear Energy and Fusion Energy

Focused Session 1 Geopolymers, Chemically Bonded Ceramics, Eco-friendly and Sustainable Materials

Focused Session 2 Advanced Ceramic Materials and Processing for Photonics andEnergy

Focused Session 3 Materials Diagnostics and Structural Health Monitoring of Ceramic Components and Systems

Focused Session 4 Additive Manufacturing and 3D Printing Technologies Focused Session 5 Single Crystalline Materials for Electrical, Optical and Medical

ApplicationsFocused Session 6 Field Assisted Sintering and Related Phenomena at High

TemperaturesSpecial Session 2nd European Union-USA Engineering Ceramics Summit Special Session 4th Global Young Investigators Forum

The proceedings papers from this conference are published in the below sevenissues of the 2015 CESP; Volume 36, Issues 2-8, as listed below.

Mechanical Properties and Performance of Engineering Ceramics and Composites X, CESP Volume 36, Issue 2 (includes papers from Symposium 1)Advances in Solid Oxide Fuel Cells and Electronic Ceramics, CESP Volume 36,Issue 3 (includes papers from Symposium 3 and Focused Session 5)Advances in Ceramic Armor XI, CESP Volume 36, Issue 4 (includes papers from Symposium 4)Advances in Bioceramics and Porous Ceramics VIII, CESP Volume 36, Issue 5 (includes papers from Symposia 5 and 9)Advanced Processing and Manufacturing Technologies for Nanostructured and Multifunctional Materials II, CESP Volume 36, Issue 6 (includes papers from Symposia 7 and 8 and Focused Sessions 4 and 6)Ceramic Materials for Energy Applications V, CESP Volume 36, Issue 7 (includes papers from Symposia 6 and 13 and Focused Session 2)Developments in Strategic Ceramic Materials, CESP Volume 36, Issue 8 (includes papers from Symposia 2, 10, 11, and 12; from Focused Sessions 1 and 3); the European-USA Engineering Ceramics Summit; and the 4th Annual Global Young Investigator Forum

The organization of the Daytona Beach meeting and the publication of these pro-ceedings were possible thanks to the professional staff of ACerS and the tireless

xii · Advances in Solid Oxide Fuel Cells and Electronic Ceramics

dedication of many ECD members. We would especially like to express our sincerethanks to the symposia organizers, session chairs, presenters and conference atten-dees, for their efforts and enthusiastic participation in the vibrant and cutting-edgeconference.

ACerS and the ECD invite you to attend the Jubilee Celebration of the 40th In-ternational Conference on Advanced Ceramics and Composites (http://www.ceram-ics.org/daytona2016) January 24-29, 2016 in Daytona Beach, Florida.

To purchase additional CESP issues as well as other ceramic publications, visitthe ACerS-Wiley Publications home page at www.wiley.com/go/ceramics.

JINGYANG WANG, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, China

SOSHU KIRIHARA, Osaka University, Osaka, Japan

Volume EditorsJuly 2015

Advances in Solid Oxide Fuel Cells and Electronic Ceramics · xiii

Solid Oxide Fuel Cells

3

EFFECTS OF TiO2 ADDITION ON MICROSTRUCTURE AND IONIC CONDUCTIVITY OF GADOLINIA-DOPED CERIA SOLID ELECTROLYTE M. C. F. Dias and E. N. S. Muccillo Energy and Nuclear Research Institute PO Box 11049, Pinheiros, S. Paulo, 05422-970, SP, Brazil ABSTRACT

Ceria containing trivalent rare-earth is a solid electrolyte with higher ionic conductivity than the yttria fully-stabilized zirconia standard ionic conductor. This feature turns these ceria-based ionic conductors promising materials for application in solid oxide fuel cells operating at intermediate temperatures (500-700ºC). One of the most utilized approaches to optimize the electrical conductivity and other properties of these materials is the introduction of a second additive. In this work, ceria-20 mol% gadolinia with additions of TiO2 was prepared by solid state reaction. The main purpose was to investigate the effects of the additive on densification, microstructure and electrical conductivity of the solid electrolyte. Sintered pellets were characterized by evaluating apparent density, X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and electrical conductivity by impedance spectroscopy. The additive was found to influence all studied properties. Increase of densification was obtained with TiO2 addition. This additive promotes increase of the blocking of charge carriers at the grain boundaries due to solute exsolution and formation of the pyrochlore Gd2Ti2O7 phase at grain boundaries for contents in excess of the solubility limit. INTRODUCTION

Polycrystalline ceramics based on cerium dioxide have attracted much attention over the last decades from both theoretical and experimental point of views, due to their wide range of applications. Some of the well know applications of cerium-based ceramics are as catalysts for chemical reactions 1, mechanical polishing media in microelectronics 2, as gas sensor 3, as solid electrolyte and electrode in solid oxide fuel cells 4, luminescent material 5 and as ultraviolet filter and blocker 6,7.

Additives in cerium dioxide have been used for changing a specific property. The addition of trivalent rare earth, for example, results in a substantial increase of the ionic conductivity. The highest increase of the ionic conductivity in cerium dioxide based solid solutions has been obtained with samarium and gadolinium. The ionic conductivity of Gd-doped ceria at 800ºC is similar to that of yttria-stabilized zirconia at 1000ºC 8. Thus, these solid solutions have been considered for possible application in solid oxide fuel cells operating at intermediate temperatures (600-800ºC) 8.

Other additives to cerium oxide ceramics have been considered to aid the sintering process allowing for increasing the sinterability of this material along with a better microstructural design and control. Few reports may be found concerning the addition of TiO2 to doped ceria ceramics, probably because the partial substitution of Ce4+ for Ti4+ do not change the concentration of oxygen vacancies. Consequently, no influence of this additive on the ionic conductivity is expected. Jurado 9 showed that titanium oxide addition do gadolinia-doped ceria introduces a low resistivity intergranular phase, thereby the blocking of charge carriers at the grain boundaries is reduced. Cutler 10 and Pikalova 11 observed an increased densification of doped ceria with this additive. The latter also observed that a pirochlore phase with composition Gd2Ti2O7 was formed depending on the content of TiO2.

4 · Advances in Solid Oxide Fuel Cells and Electronic Ceramics

Effects of TiO2 Addition on Microstructure and Ionic Conductivity

In this work, the effects of TiO2 on the densification, microstructure and ionic conductivity of gadolinia-doped ceria was investigated, for additive contents below and above its solubility limit. EXPERIMENTAL

Ce0.8Gd0.2O2- , CGO (>99.5%, Fuel Cell Materials) and TiO2 (99.95%, Alfa Aesar) were used as starting materials. Solid solutions containing 1, 2.5 and 5 mol% TiO2 were prepared by solid state reaction. The starting materials were first dried in an oven. Afterwards they were mixed in alcoholic medium in the stoichiometric proportions. After drying, the mixtures were pressed into discs of 10 mm diameter and 2-3 mm thickness. Sintering was performed in a box type furnace (Lindberg BlueM) heating at a rate of 3 ºC.min-1 up to 1100ºC and at 5 ºC.min-1 from 1100 to 1500ºC with 3 h holding time. For comparison purposes, specimens without the additive were also prepared under the same experimental conditions.

Characterization of the sintered specimens was carried out by density measurements using the immersion method. The porosity of the sintered materials was estimated according to ASTM C20-00. The phases were characterized by Raman spectroscopy (Renishaw, InVia Raman Microscope) with a He-Ne laser with 633 nm wavelength in the 200-800 cm-1 spectral range. The microstructure of polished and thermally etched surfaces was evaluated by scanning electron microscopy (Philips, XL30) with secondary electrons. The electrical conductivity was determined by impedance spectroscopy measurements (HP 4192A) in the 5 Hz-13 MHz frequency range. Silver was used as electrode material. RESULTS AND DISCUSSION

All sintered specimens attained high density values as shown in Table 1. Addition of TiO2 allowed for increasing further the density, turning negligible the apparent porosity.

Table 1. Values of relative density and apparent porosity of sintered specimens.

Material Relative density

(%)

Porosity

(%)

CGO 97.5 0.1

CGO + 1% TiO2 99.8 ~ 0

CGO + 2.5% TiO2 98.7 ~ 0

CGO + 5% TiO2 ~ 100 ~ 0

The linear shrinkage up to 1500ºC (not shown here) is similar for both specimens (with and without titanium oxide) and amounts 23%. In addition, the additive does not change the initial temperature of shrinkage.

Figure 1 shows Raman spectra of the investigated specimens.

Advances in Solid Oxide Fuel Cells and Electronic Ceramics · 5

Effects of TiO2 Addition on Microstructure and Ionic Conductivity

0 300 600 900

Inte

nsit

y

Raman shift (cm-1)

CGO+TiO2

2.5%

1%

5%

*

Figure 1. Raman spectra of sintered specimens containing TiO2.

The Raman spectra consist of a predominant band centered at 465 cm-1 attributed to the

triple degenerated F2g mode of the fluorite lattice. Low intensity Raman bands at 550 and 650 cm-1 are usually assigned to the extrinsic oxygen vacancies created by partial substitutions 12. In the Raman spectrum of the specimen containing 5 mol% TiO2, other low intensity band at ~ 312 cm-1 is observed (indicated by *). This band is ascribed to Gd2Ti2O7 phase, which displays about six allowed Raman modes 13. This result evidences then the formation of the pirochlore phase in specimens with 5 mol% TiO2. Moreover, the formation of this crystalline secondary phase reveals that when the concentration of the additive exceeds the solubility limit in the ceria matrix, it induces the exsolution of the dopant (gadolinium) from the solid solution. It is worth noting that no other phase than the cubic fluorite characteristic of ceria was detected by conventional X-ray diffraction measurements, possibly due to the experimental limitations of that technique.

Figure 2 shows a scanning electron microscopy micrograph (a) and an impedance spectroscopy diagram of the base material after sintering at 1500ºC for 3 h.