bluuebunny/crossref_metadata_2025 huggingface dataset:
A Case Study Analysis of System Efficiency, Viability and Energy Values of SOFC Based Fuel Cell Micro-CHP for Office Buildings
Authors: Tesfai Alem Teklebrhan , Mylona Anastasia , Connor Paul , Cassidy Mark , Irvine John T. S.
Published: July 2015

The built environment is a large contributor to the greenhouse gas emissions. The first step in tackling environmental impact and fuel cost reduction is the minimization of energy losses through introduction of new and more efficient energy conversion technologies. In this study, the potential application of fuel cell micro-CHP in a typical office building is investigated. A 1.5 k Welfuel cell micro-CHP has been installed in an office building at CIBSE headquarters (HQ). The unit converts natural gas to electricity, using Solid Oxide Fuel Cell (SOFC) stack. The installation and data from the operation of the system is discussed. The data shows that the heat recovered from the SOFC stack covers most of the domestic hot water requirement of the office building, requiring minimal top-up from the immersion heater.
Microtubular SOFC (mSOFC) System in Truck APU Application
Authors: Kendall Kevin , Newton Jill , Kendall Michaela
Published: July 2015

The purpose of this paper is to discuss three novel ideas applied to the SOFC APU truck application:- replacing the planar stacks with microtubular SOFCs to give greater robustness; downsizing to 100We to allow more rapid evolution; and focusing on dual fuel trucks using Liquid Natural Gas (LNG) to avoid diesel reforming for the SOFC. An EU project was initiated in 2014 to develop these ideas under the heading SAFARI (Sofc Apus For Auxiliary Road-truck Installations) funded by FCH-JU with 6 partners in the UK, Switzerland, Spain and Poland. This paper describes results from the first 18 months of the project and shows that mSOFCs operating on LNG trucks could give significant impact.
Development of Micro Power Generator Using LPG-Fueled Microtubular Solid Oxide Fuel Cells
Authors: Sumi Hirofumi , Yamaguchi Toshiaki , Suzuki Toshio , Shimada Hiroyuki , Hamamoto Koichi , Fujishiro Yoshinobu
Published: July 2015

Solid oxide fuel cells (SOFCs) can, in principle, directly use hydrocarbon fuels such as methane and liquefied petroleum gas (LPG). It was previously found that nickel-gadolinia doped ceria (Ni-GDC) anode has high durability under LPG utilization in SOFCs. However, the performance under direct LPG utilization was low compared to hydrogen fuel, because anode polarization resistance increased by internal reforming. Carbon was slightly deposited on the Ni-GDC anode after direct LPG utilization for 100 h at 650 oC. In this work, a catalytic partial oxidation reformer was developed for LPG utilization, and high performance was obtained using reformate gas as well as hydrogen without carbon deposition on the Ni-GDC anode for 100 h at 650 oC. Furthermore, microtubular SOFC stacks were developed using mass production technologies, and a proto-type 200 W micro power generator was demonstrated via NEDO project entitled "Technology Development for Promoting SOFC Commercialization".
Status of Light Weight Cassette Design of SOFC
Authors: Margaritis Nikolaos , Blum Ludger , Batfalsky Peter , Bohmann Dirk , Ceschini Sergio , Fang Qingping , Federmann Dirk , Kroemer Joachim , Peters Roland , Steinberger-Wilckens Robert
Published: July 2015

Lightweight SOFC stacks are currently being developed especially for automotive applications such as APU and for portable devices. Within the EU funded project MMLCR=SOFC the Jülich lightweight so-called CS-design was improved concerning better suitability for glass sealing, reduced manufacturing effort and increased power. Based on modelling in combination with manufacturing experience, test results, and post-test analysis substantial changes of the previous CS-design were made. The manufacturing of single parts, particularly due to the improved design of sheet metal interconnects, as well as the assembling processes are suitable for low-cost mass manufacturing. The novel decal concept of glass-ceramic sealant screen printed on foil in order to produce green tapes is used for joining the stack layers offering an enormous potential for cost savings in industrial assembly process. First stack tests with the new CSV–design showed a comparable electrochemical performance to the previous CSIV design having at the same time a better thermo-mechanical behavior.
Thermal Integration of SOFC and Plate Heat Exchanger Desorber
Authors: Venkataraman Vikrant , Pacek Andrzej W , Steinberger-Wilckens Robert
Published: July 2015

A Plate Heat Exchanger (PHE) desorber is thermally integrated with an SOFC stack via a specially designed tube in tube heat exchanger with internal fins in which thermal oil is heated to the required desorber temperature and then serves as the coupling fluid in the PHE desorber. A modelling approach has been adopted where the PHE desorber is solved for heat and mass transfer using MATLAB & EES and the tube in tube heat exchanger with internal fins has been modelled and optimized using COMSOL multiphysics. The results show that the PHE desorber is able to produce the required quantity of refrigerant needed for a 1 kW cooling load. The use of PHEs as desorbers not only gives a high heat transfer surface area but also leads to considerable reduction in desorber volume when compared to conventional falling film desorbers.
Thermodynamic Performance of a High Efficient Power Plant Based on Faecal Biomass Gasification, Solid Oxide Fuel Cells and Micro Steam Turbine
Authors: Recalde Mayra , Woudstra Theo , Liu Ming , Aravind P.V.
Published: July 2015

Affordable sanitation around the world with the recovery of valuable energy and clean water from faecal biomass in an off-grid system is a challenge. A novel small scale combined heat and power (CHP) toilet system concept has been optimized which generate power very efficiently and produce clean water. The system combines a dryer, a plasma gasifier, and a gas cleaning unit with an ambient pressure solid oxide fuel cell (SOFC) stack and a micro steam turbine (MST). The gasifier uses additional heat supplied from the combustion of stack depleted fuel. With this concept, syngas with high heating value can be produced which can be efficiently converted in a SOFC system. This is reflected by the net electrical efficiency of the integrated system configuration of the order of 40%. Additional power is produced combining it with an MST and an efficiency increase of the order of 20% is achieved.
Analysis of Performance Limiting Factors in Solid-Oxide Iron-Air Redox Battery Operated with Different Redox Couples
Authors: Jin Xinfang , Zhao Xuan , White Ralph E. , Huang Kevin
Published: July 2015

The present computational study investigates the factors limiting the performance of a newly developed solid oxide iron-air redox battery (SOMARB) operated at 800 and 500oC, thus with different redox couples, viz. Fe/FeO for 800oC and Fe/Fe3O4 for 550oC. The multiphysics model established is considered high fidelity since it has been validated by experimental data obtained under conditions similar to the simulations. The effects of current density, initial porosity of redox cycle unit (RCU), distance between Reversible Solid Oxide Fuel Cell (RSOFC) and RCU, and depth of discharge on the battery’s performance have been systematically studied. It is found that the performance limiting factor is the electrolysis electro-kinetics of RSOFC for the 800oC-battery and Fe3O4-reduction kinetics of RCU for the 550oC-battery, respectively. Strategies with the goal of achieving a balanced energy capacity and cycle efficiency are also proposed.
Integrated Air Preheater and Anode Off-Gas Oxidizer
Authors: De Vos Yves , Janssens Jean-Paul
Published: July 2015

The performance of a cathode air preheater with internal off-gas oxidation is presented. It is a plate heat exchanger, handling both injection and oxidation of depleted anode gas in the hot cathode flow. The gas mixture oxidizes in the heat exchanger, and the reaction heat is used to preheat cathode air. We describe a system consisting of a close coupled injector and a catalytically coated plate heat exchanger. The performance was constrained by reaction kinetics: the off-gas and cathode mixture ignites within 5 – 10 ms at mixture temperatures above 750°C, causing overheating of the exchanger walls. The integrated component consists of an internal injector, which delivers the anode gas to each cathode flow path between pairs of heat exchanging plates. The injection occurs adjacent to a catalytically coated zone in the heat exchanger. The CFD effort covers the combined effects of injection, mixing, generation of reaction heat and heat exchange.
Thermodynamic Evaluation of Integrated Heat-Pipe Reformer SOFC System
Authors: Herrmann Stephan , Jimenez Arreola Manuel , Gaderer Matthias , Spliethoff Hartmut
Published: July 2015

Optimized integration of SOFC and gasification offers the potential for highly efficient electricity generation from renewable solid feedstock. In the presented integration approach heat pipes are used to transport heat from the SOFC to a biomass gasifier. Combined with further system optimization measures an electrical efficiency of 61.2% is achieved.
Analysis of a Solid Oxide Fuel Cell System with Low Temperature Anode Off-Gas Recirculation
Authors: Engelbracht Maximilian , Peters Roland , Blum Ludger , Stolten Detlef
Published: July 2015

At Forschungszentrum Jülich an SOFC system with anode off-gas recirculation loop operating at temperatures up to 160 °C is simulated. To analyze the effect of anode off-gas recirculation, a dynamical system model was implemented in Matlab/Simulink®. The results show, that the recirculation rate has a significant effect on the electrical efficiency. In principle, at constant current density high recirculation rates decrease the cell voltage and increase the power demand of the recirculation blower. Therefore, the highest electrical efficiency can be reached with high system fuel utilization, low recirculation rate and in consequence high stack fuel utilization. On the other hand less amount of steam is available for the reforming reaction at low recirculation rates. Therefore, the minimum recirculation rate is determined by the risk of carbon formation. An optimal operation range to avoid carbon formation and to ensure a high electrical efficiency requires recirculation rates between 65 and 70 % and system fuel utilizations above 90 %.
Numerical Simulation of SOFC System Performance at 90% Fuel Utilization with or without Anode Off-Gas Recycle for Enhancing Efficiency
Authors: Tanaka Yohei , Terayama Takeshi , Momma Akihiko , Kato Tohru
Published: July 2015

To investigate possibility to enhance electrical efficiency, performance of methane-fueled 10 kW SOFC systems was numerically simulated with calculated voltage-current-density curves at 750ºC of a single cell with a bipolar plate, which approximated a stack performance. Operation at 90 % fuel utilization (U
f) with anode off-gas recycle (AGR) and with steam reforming (no recycle) led to 75-67 %-LHV and 72-66 %-LHV DC electrical efficiency at 0.05-0.40 A/cm2, respectively. System simulations considering heat loss from a stack clarified that 750ºC stack temperature can be maintained at 0.12-0.40 A/cm2 and 64-59 % and 63-59 % net AC electrical efficiency will be attainable at U
f = 90% with and without AGR, respectively. Furthermore, enhancement of net AC efficiencies was found to be 10 percentage points at those current densities against ones of a conventional system using steam reforming at U
f = 73 %.
Effects of SOFC Exhaust Gas Recirculation on Performance of Solid Oxide Fuel Cell-Gas Turbine Hybrid System Utilizing Renewable Fuels
Authors: Saebea Dang , Authayanun Suthida , Patcharavorachot Yaneeporn , Arpornwichanop Amornchai
Published: July 2015

The use of biogas and ethanol as fuel for solid oxide fuel cell-gas turbine (SOFC-GT) hybrid system needs of the external steam reformer. As the steam reformer and air preheater are units that require high external energy input, the efficient heat management of the SOFC system is necessary. Thus, the aim of this study is to analyze the recycling of the SOFC exhaust gas in the SOFC-GT hybrid system supplying fuels as ethanol and biogas. The effect of the recirculation ratio of the anode exhaust gas on the performance of SOFC-GT hybrid system, i.e., the SOFC efficiency, the turbine to SOFC power ratio, and the overall efficiency of hybrid system was firstly investigated. Additionally, the recirculation of both anode gas and cathode gas in the SOFC-GT hybrid system was studied.
Analysis of Transient Behavior of Fuel Reformer to Fuel Supply Variation in Solid Oxide Fuel Cell Systems with Anode Off-Gas Recycle
Authors: Terayama Takeshi , Momma Akihiko , Tanaka Yohei , Kato Tohru , Hoshi Nobukazu
Published: July 2015

In the case of increasing fuel supply to solid oxide fuel cell (SOFC) systems, mass transport delay generally occurs in reformers and SOFCs. Therefore, heat used for fuel reforming becomes larger than heat supplied to reformers, and reformer heat tends to be absorbed. In this paper, transient behavior of reformers in SOFC systems with anode off-gas recycle, in the case of increasing fuel supply, is analyzed by numerical simulation. As a result, it is suggested that reformer temperature decreases from several to several tens of K, when heat is absorbed from the reformer, which is small scale, lightweight and has low heat capacity, for several seconds. In addition, methane flow rate outputted from the reformer increases, and carbon deposition occurs, depending on conditions. This paper will present details of these results and discuss methods to prevent carbon deposition and increase of CH4 output from the reformer.
Assessment of Possibilities for Operation of Ni-Catalyst Partial Oxidation Reformers in SOFC Systems after Soot Formation
Authors: Baskakov Albert Pavlovich , Plotnikov Nikita , Wang W. , Peng J. , Volkova Yulia , Dong Z , Lu X , Luo Q
Published: July 2015

Solid oxide fuel cells (SOFCs) allow us to directly convert the chemical energy of fuel into electricity. With their emissions consisting mainly of Н2О and СО2, SOFC-based power generation systems are highly efficient (with efficiency up to 70%) and friendly to the environment, which makes them increasingly attractive for the use in stationary power generation systems. The mixture of CO and H2 (synthesis gas) supplied to the SOFC anode can be produced from the natural gas using the dry or steam reforming or the partial oxidation methods. The partial oxidation of methane, which is typically done with Ni catalysts, seems the best option for start-up systems of power plants with the anode gas recirculation or other applications where no water supply can be arranged. In this case, carbon deposition on the parts of reformer can be a problem, particularly, where the air-gas mixture supply system works abnormally.
Sensitivity Analysis for the Efficiency Improvement of a Light Integrated Gasification Fuel Cell Power Plant
Authors: Taufiq Bin Nur , Kikuchi Yasunori , Ishimoto Takayoshi , Honda Kuniaki , Koyama Michihisa
Published: July 2015

The solid oxide fuel cell (SOFC) is recognized as one of high efficiency plants of electricity generation for a sustainable future system with low environmental impact. In term of fuel flexibility, SOFC is suitable for direct use of syngas from a coal gasification plant. The application of integrated SOFC in coal gasification based power plant, such as a light integrated gasification fuel cell (L-IGFC) power plant, could be one of the most promising coal energy conversions system providing high electrical efficiency with low CO2 emitted to the atmosphere. The system consists of a coal gasifier and SOFC module on the top of a steam turbine. The sensitivity analyses of major operating parameters were performed using the developed model. The results indicated that the L-IGFC plant could achieve electrical efficiency in the range of 46.35- 60.32% in lower heating value.
Catalytic Total Oxidation of SOFC Exhaust Gas on Cu-Mn Catalysts
Authors: Sung Jae Gi , Song Ki Hun , Chung Jong Shik , Sammes Nigel Mark
Published: July 2015

SOFC exhaust gas oxidation technology will contribute to reducing the pollutants and providing economically feasible SOFC systems. The Cu-Mn based materials, known as CO and H2 oxidation catalysts, were tested as novel metal-free SOFC exhaust gas oxidation catalysts. Catalysts are prepared with incipient wetness impregnation method using metal nitrate precursors on γ-Al2O3. Various Cu-Mn catalysts are also prepared to study the effect of CuO-MnO ratio on catalytic activity. The feed gas was synthesized as similar composition of SOFC exhaust gas. The optimized conversion was obtained when CuO and MnO had the same weight ratio(CuO/MnO wt. ratio = 1). The conversion of CO, H2 and CH4 is 43.4, 36.1 and 58.0, repectively.
Synthesis, Characterization and Performance of Calcium and Samarium Co- doped Ceria Electrolytes for Low and Intermediate Temperature Solid Oxide Fuel Cells
Authors: Pandey Dyuti , Basu Suddhasatwa
Published: July 2015

Three different compositions of samarium and calcium co-doped ceria were synthesized by cation-complexation process. The calcium content in co-doped Ce0.8Sm0.2-xCaxO2-δ varied from x=0.5 to 0.15. The effects of variation in calcium content on phase, crystallite size and morphology of the synthesized powders were investigated by XRD, SEM and TEM analyses. All synthesized powders were fluorite-type ceria nano-solutions. The particle size of Ce0.8Sm0.15Ca0.05O2-δ was around 10-17 nm as seen in TEM. To evaluate the electrochemical behavior the synthesized powders were die-pressed into pellets and sintered at 1450 °C for 10 hours. At 550°C, out of the three synthesized compositions, Ce0.8Sm0.15Ca0.05O2-δ showed the highest conductivity of 0.013 S/cm. Half cells, Ce0.8Sm0.2-xCaxO2-δ /NiO-Ce0.8Sm0.2-xCaxO2-δ have been fabricated and tested for the purpose of investigating their potential use in low and intermediate temperature SOFCs.
Characterization of Terbium and Samarium Co-Doped Ceria Films as SOFC Electrolyte Prepared by Using Ultrasonic Spray Pyrolysis Method
Authors: Vestli Mihkel , Nurk Gunnar
Published: July 2015

Tb and Sm cations binary co-doped ceria films were deposited using the ultrasonic atomizing spray pyrolysis method. The crack-free homogenous films with different dopant concentration were deposited and thereafter annealed at fixed temperatures 900, 1200 and 1300 °C, respectively. The Ce0.9Sm0.1-xTbxO2-δ films formed were analyzed using X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy, atomic force microscopy and four probe dc technique. It was demonstrated that several microstructural parameters of oxide films are controlled by the sintering temperature and Tb dopant ions. Electrical properties like activation energies of ionic and electronic conductivity of the Ce0.9Sm0.1-xTbxO2-δ films were also influenced by the film composition.
Praseodymium Doped Ceria: The Role of 4f-Electrons of Pr Dopant in Doped Ceria
Authors: Alaydrus Musa , Sakaue Mamoru , Linh Nguyen Hoang , Aspera Susan Meñez , Wungu Triati Dewi Kencana , Kasai Hideaki
Published: July 2015

Oxides like ceria (CeO2) are very promising for solid electrolyte materials when doped by suitable aliovalent dopants, as they introduce high oxygen ion conduction leading to intermediate to low temperature operations (T ≤ 800°C ). Over the past decades, engineering new compositions aiming at high ionic conductivity at lower operating temperatures has been a key issue of developing solid oxide fuel cells. However, the understanding over the underlying physics on the oxygen ion conduction in this system remains unclear. In this work, we discuss our DFT+U study on the effect of the 4f-electrons on Pr-doped CeO2. We found that, regardless of their localized nature tendency, we found significant contributions from the Pr-dopant 4f-electrons to the oxygen vacancy formation energy as well as the preferential site of the oxygen vacancy formation in comparison with the model of fully localized 4f-electrons, though the geometrical properties for each local minimum structure remain unaffected.
High Temperature Strength and Elastic Properties of Doped Ceria under Various Oxygen Partial Pressures
Authors: Taguchi Takahiro , Watanabe Satoshi , Sato Kazuhisa , Hashida Toshiyuki
Published: July 2015

Fracture strength and Young’s modulus of cerias doped with 10 mol.% Gd and 10, 20 and 30 mol.% Y and yttria stabilized zirconia were investigated by means of small punch testing method under controlled the temperature (1073 K) and the oxygen partial pressure (log((p(O2)/atm)= -1.1, 17.5, -21.4, -22.0). Under the reducing conditions, the color of fractured doped ceria specimen changed from pale yellow to gray, by contrast, no oxygen partial pressure dependence of changes in color were observed on yttria stabilized zirconia. It is therefore indicated that oxygen nonstoichiometry affects mechanical properties of the doped ceria. Compared with the high oxygen partial pressure (log(p(O2)/atm)= -1.1), under the low oxygen partial pressure the Young’s modulus of all the specimens decreased monotonically. The fracture strength, by contrast, increased at log(p(O2)/atm) = -17.5, and under the lower oxygen partial pressure, different variation trends showed each yttria doped cerias with Y contents. From scanning electron microscopy (SEM) observation, an increasing transgranular fracture was observed in the specimen at the fracture strength increasing region. The oxygen partial pressure dependence of the fracture strength of doped ceria could be arranged as a function of the reduction expansion of the lattice constant a/a
0, it has a maximum value at around a/a
0 = 0.30 %. It is suggested that there is a trade-off between weakening electrostatic bonding force caused by chemical expansion of lattice constant and strengthening caused by inhomogeneous structural change resulting from partial reduction of Ce4+ to Ce3+.
Effects of Copper Oxide Addition on the Electrochemical Properties of Samarium Doped Ceria Electrolyte for Intermediate Temperature Solid Oxide Fuel Cells
Authors: Toor Sannan Yousaf , Croiset Eric
Published: July 2015

Low temperature sintering of samarium doped ceria (Sm0.2Ce0.8O1.9, SDC) can help in incorporation of metal as a support in low temperature solid oxide fuel cells. Sintering aids (mostly transition metal oxides) can be used to substantially reduce the sintering temperature which also has an effect on the overall electrochemical process. Here, 0-10 mol% of copper oxide is added to the ceria solid solution through glycine nitrate combustion process and sintered at different temperatures ranging between 1000 and 1450°C. Hebb-Wagner polarization method and Electrochemical Impedance Spectroscopy (EIS) are used to separately characterize total, ionic and electronic conductivities. Results show that the 5% CuO/SDC sintered at 1100°C leads to similar total conductivity as pure SDC sintered at 1450°C, while reducing by about one-third the electronic conductivity, which is expected to contribute to reducing the mixed ionic/electronic nature of the SDC electrolyte.
Advanced Impedance Spectroscopy Study of the Influence of the Crystalline Structure on the Ionic Conduction of Thin Solid-State Electrolytes
Authors: Fernandez Macia Lucia , Van Laethem Dries , Van Steenberge Sigelinde , Depla Diederik , Deconinck Johan , Hubin Annick
Published: July 2015

In this work, an experimental and modeling approach that considers the crystalline nature of the material is used to u the electrical behavior of thin film solid state electrolytes. In this research, the complex electrical properties at different temperatures of nanocrystal yttrium-doped ceria (YDC) are determined by electrochemical impedance spectroscopy (EIS). The impedance modeling provides a description of the electrical behavior of the material. The influence of the geometry of the electrodes in the electrical measurements is investigated by finite element simulations for different electrode spacing. The combined analysis represents a strong approach to elucidate the experimental evidence that is not explained by the available physical models.
Effect of Ceria Content of CeScSZ Powder on the Phase Stability and Electrical Conductivity of SOFC Electrolyte
Authors: Choi Seung-Woo , Kim Kyeong-Joon , Kim Min-Young , Lim Jinsub , Yang Seung-Hoon , Kim Yu Sin , Kim Ho-Sung
Published: July 2015

The CeScSZ powders with ceria-doped content were synthesized by the co-precipitation process. The crystal lattice parameter and XRD peak pattern of powders were investigated with the increase of calcination temperature and the change of ceria-doped content at a certain calcination temperature. Moreover, ionic conductivities of the CeScSZ powders were also studied at the range of 500 to 900 °C. Electrolyte film was fabricated using the synthesized 1Ce10ScSZ powder and single cell of SOFC with anode-supported electrolyte was fabricated by a tape casting and co-sintering process. As a result, the SOFC cell showed power density of 1.2 W/cm2 at 2 A/cm2, 800 °C with low ohmic resistance of under 0.1 Ω·cm2.
Effect of Bismuth Oxide as Sintering Aid for Gadolinia-doped Ceria at 1050°C
Authors: De Marco Vincenzo , Sglavo Vincenzo Maria
Published: July 2015

The addition of small amount of metal oxides can increase the sinterability of Gadolinia-doped Ceria, thus reducing the temperature necessary for its densification. Here, the effect of bismuth oxide as sintering aid is studied by means of dilatometry, porosity and density measurement on samples obtained by uniaxial pressing, with the aim of achieving a microstructure with no interconnected porosity, suitable for realizing a gas tight electrolyte for SOFC. The effect of Bi2O3 load and holding time at high temperature was studied. The most promising doping concentration (6 mol%) is identified and the densification was accomplished more than 400°C below the sintering temperature of GDC10, this allowing the cosintering with copper-based cermet anode.
Single Cubic Phase Scandia-Stabilized Zirconia: Stabilization and Aging at 600oC
Authors: Santos Emanuelle Zangerolame , Muccillo R.
Published: July 2015

ZrO2:10 mol% Sc2O3 was mixed to MnO2 to evaluate its effect on cubic phase stabilization, oxide ion conductivity and aging at 600oC. Pressed ceramic pellets of zirconia stabilized with 10 mol% scandia with addition of 1.0, 2.0 and 2.5 mol% MnO2 were sintered at 1500 °C/2 h. In situ high temperature X-ray diffraction data were collected to follow the rhombohedral-to-cubic transition. Polished and thermally etched surfaces of the sintered pellets were observed in scanning electron microscope. Impedance spectroscopy measurements were carried out. The single cubic structure is achieved for the specimen with 2 mol% MnO2 nominal addition. The electrical conductivity of this specimen was monitored at 600 oC for 100 days. The ionic conductivity value remained constant, suggesting its use as solid electrolyte in SOFCs operating at that temperature.
Fabrication of Thin-Film Yttria-Stabilized Zirconia Electrolyte by Aerosol-Assisted Chemical Vapor Deposition
Authors: Jang Dong Young , Kim Manjin , Kim Hyun Joong , Bae Kiho , Kim Jun Woo , Shim Joon Hyung
Published: July 2015

In this work, fully dense yttria stabilized zirconia (YSZ) electrolyte films under thickness of 1 μm are successfully fabricated on the anode-supported solid oxide fuel cells (SOFCs) by aerosol assisted chemical vapor deposition (AACVD), which is a type of chemical vapor deposition but conducted in an open atmospheric air not requiring expensive vacuum processes. SOFCs with thin film AACVD YSZ electrolytes marked 720 mW/cm2 at 650°C as the maximum power in our test with open circuit voltage over 1 V. We expect that this result will contribute to cost-effective production of high performance low temperature SOFCs.
Dominant Factors Influencing the Electrochemical Performance of Plasma-Sprayed LSGM Electrolyte
Authors: Zhang Shan-Lin , Li Cheng-Xin , Li Chang-Jiu
Published: July 2015

Atmospheric plasma spraying (APS) is promising to fabricate functional layers for solid oxide fuel cells (SOFCs). In this article, the factors dominating the performance of APS Mg/Sr-doped lanthanum gallate (LSGM) electrolyte for intermediate-temperature SOFCs will be introduced based on our recent systematic investigation. It is found that the evaporation of Ga during plasma spraying is significantly influenced by spray particle size, which remarkably affects the properties of plasma-sprayed LSGM deposit. Moreover, it is revealed that the application of the critical deposition temperature concept to the deposition of LSGM results in the fabrication of a dense LSGM with excellent lamellar bonding. The dense LSGM electrolyte exhibits an ionic conductivity of ~80% sintered bulk LSGM. The electrochemical performance test confirms that the SOFC cell assembled with APS LSGM electrolyte shows high performance with a maximum output power density of 710 mW/cm2 at 800oC using H2/air. Thus, it is possible to prepare superior LSGM electrolyte membranes by APS.
Grain Size Effect on Conductivity of LSGM Thin Film Electrolyte for Solid Oxide Fuel Cell
Authors: Endo Yoichi , Dempoh Akishi , Terai Takayuki , Suzuki Akihiro
Published: July 2015

The grain size effect of La0.9Sr0.1Ga0.8Mg0.2O3-δ (LSGM) electrolyte thin film was investigated in order to clarify the mechanism of the change of ion conductivity of thin film. The film was deposited on a LaSrGaO4 (LSGO) substrate by radio frequency magnetron sputtering and then annealed at 900 oC or 1100 oC to change the grain size in the film. The mean grain size in the films annealed at 900 oC and 1100 oC was 80 nm and 281 nm, respectively. The ion conductivity was measured by electrochemical impedance spectroscopy (EIS). The ion conductivity values of the film of the mean grain size of 80 and 281 nm at 800oC were σ=1.34×10-2 and 1.81×10-2 S/cm, respectively. The activation energy value of both films was 1.08 eV. The grain boundary conductivity obtained by applying the Brick-layer model was nearly two orders of magnitude lower than the bulk conductivity. The activation energy value of the grain boundary conductivity was 1.33 eV. The resistance to transport the ions across the grain boundary should be high. The higher conductivity of the 1100 oC annealed film derives from the decrease of the high resistive grain boundary density.
Influence of Substrate on Conductivity of Sr and Mg Doped Lanthanum Gallate Thin Film Electrolyte for Solid Oxide Fuel Cell
Authors: Dempoh Akishi , Endo Yoichi , Terai Takayuki , Suzuki Akihiro
Published: July 2015

In order to reveal the influence of substrate on the conductivity change of La0.9Sr0.1Ga0.8Mg0.2O3-δ (LSGM) thin film from the bulk, we prepared LSGM thin films on the sapphire and the quartz substrates by radio frequency magnetron sputtering, and evaluated the crystallinity, the microstructure, and the conductivity. The lattice constant of 0.6 μm thick film was different between the substrates. Compared with the bulk, the lattice constant of the thin film on the sapphire substrate was decreased 1.3%, and that on the quartz substrate was increased 0.7%. The grains in the thin film on the quartz substrate were approximately 0.2 μm in size, and those on the sapphire substrate were approximately 0.1 μm in size. The conductivity was measured at 710 °C by electrochemical impedance spectroscopy. The conductivity of the thin film on the quartz substrate was σ = 2.2 × 10-3 Scm-1 and that on the sapphire substrate was 9.0 × 10-4 Scm-1. The reason why the thin film on the quartz substrate had higher ion conductivity than that on the sapphire substrate can be attributed to the higher density of the grain boundaries which govern the total resistivity of the film on the quartz substrate than that on the sapphire substrate.
Understanding the Aging Degradation of Doped Barium Cerate Proton Conductor in Ambient Air at Room Temperature
Authors: Yan Ning , Gao Tong , Wang Wei , Luo Jing-Li
Published: July 2015

In this work, we report that doped barium cerate proton conductor was prone to a gradual decomposition in ambient air at room temperature under atmospheric CO2 and low humidity level. Via using a variety of materials characterization techniques including XRD, SEM, TEM, STEM-EDX and TGA-DSC, it was confirmed that the adsorbed H2O initiated and promoted the decomposition of the doped cerate, subsequently leading to the formation of BaCO3 nanorods as the major impurity, presumably following a microcrucible mechanism. The influences of the sintering temperature, Zr doping ratio and air relative humidity of were also investigated.
Influence of Sintering Additive on the Electrical Conductivity, Chemical Stability and Sinterability of BaCe0.55Zr0.3Y0.15O3-δ
Authors: An Hyegsoon , Shin Dongwook , Choi Sung-Min , Hong Jongsup , Yoon Kyung Joong , Son Ji-Won , Kim Byung-Kook , Lee Jong-Ho
Published: July 2015

In this study, BaCe0.55Zr0.3Y0.15O3-δ was synthesized via solid state reaction (SSR) method and successfully sintered at relatively low temperature below 1400 oC using various types of nickel oxide additives (simple oxide form, NiO and compound form, BaY2NiO5). In order to compare the effect of different form of sintering additives, we investigate the electrical conductivity, chemical stability and sinterability via dilatometery, DC 4-probe conductivity measurement, XRD and TG analysis. In addition to the experimental results, possibility and limitation of compound form of sintering aid will also be addressed in this paper.
Comparative Study of BaY0.1Ce0.9O3-δ Membrane with BaY0.1Zr0.9O3-δ Protective Layers Synthesized with Spray Pyrolysis and Magnetron Sputtering Methods
Authors: Maide Martin , Korjus Ove , Vestli Mihkel , Romann Tavo , Nurk Gunnar
Published: July 2015

Chemically stable BaY0.1Zr0.9O3-δ (BZY) layers were deposited onto the BaY0.1Ce0.9O3-δ (BCY) substrate using reactive magnetron sputtering and spray pyrolysis method. Dense supportive BCY substrates with good phase purity were made from BCY nanopowder synthesized from nitrate salt solutions using 2.4 MHz ultrasonic particle generator. Protective BZY layer deposited using magnetron sputtering method was approximately 0.7 mm thick, highly dense, with good phase purity and with no cracks. Spray pyrolyzed BZY layer was approximately 2-3 mm thick, with good phase purity and with some closed porosity. Electrochemical properties of BCY membrane with and without protective BZY layers were studied. Lowest activation energy (0.35 eV) was obtained for pure BCY membrane based system. Membranes with magnetron sputtered BZY coating have activation energy equal to 0.35 eV and 0.40 eV for spray pyrolized layer. Studied membranes were exposed to CO2 at 700 °C and found to be protective for the BCY.
Low Temperature Synthesis of Sub-micrometer Yttria-doped Barium Zirconate Thin Films by Modified Chemical Solution Deposition Technique
Authors: Biswas Mridula , Xie Hanlin , Su Pei-Chen
Published: July 2015

Yttria-doped barium zirconate (BZY) electrolyte films with sub-micrometer thickness were prepared using a modified chemical solution deposition (CSD) technique at very low sintering temperature of 800 °C without sintering aid. Pure perovskite BZY phase without barium carbonate associated with low calcination temperature was successfully obtained with no obvious barium (Ba) evaporation to deviate the stoichiometry composition. This cost effective and scalable method for BYZ as compared to the other reported vacuum-based thin film deposition techniques such as pulsed laser deposition (PLD) or atomic layer deposition (ALD) are potentially applicable in the fabrication of high quality electrolyte for nano-thin film micro solid oxide fuel cells operating at temperature below 500 °C.
Cell Performance of Anode-Supported BaZr0.85Y0.15O3-δ/Carbonate Composite Electrolyte at Intermediate Temperature
Authors: Kim Ji-Tae , Park Ka-Young , Park Jun-Young
Published: July 2015

Anode-supported solid oxide fuel cells are constructed with a two-phase composite electrolyte consisting of a BaZr0.85Y0.15O3-
δ (BZY) and alkali carbonates (Li-0.5Na)2CO3. These cells are designed to enhance cell performance in the power density at intermediate temperatures. Cells with the composite electrolytes are fabricated by the co-pressing technique; the Ni-cermet material is used as the anode, while the lithiated NiO is used as the cathode. Using carbonate phases, dense composite BZY are fabricated and uses as an electrolyte at a remarkably low sintering temperature of 600 °C. The maximum power density of this single cell is 85 mW cm-2 at 550°C. This power density is attained at a high open-circuit voltage of 1.01 V.
Evaluation of Gadolinium Doped Barium Zirconate Electrolyte for Solid Oxide Fuel Cell
Authors: de Florio Daniel Zanetti
Published: July 2015

In this work gadolinium doped barium zirconate (gadolinium oxide = 0, 5, 10, 15 and 20% mol) was prepared by Pechini method from nitrate precursors. The powders were studied by simultaneous thermal analysis, X-ray diffraction, and scanning electron microscopy. These powders were then uniaxially pressed in cylindrical discs. The pellets were sintered at temperatures of 1773 K/1 h and 1523 K/1 h with and without amounts of boric acid as sintering aid, respectively. The parallel faces of each sample were painted with platinum paste and electrically characterized by impedance spectroscopy in the frequency range from 1 MHz to 1Hz, under static air and standard mixture (3% hydrogen/97% nitrogen) flow, up to 1273 K. The main results indicate that dense (>96 % of theoretical density) barium zirconate perovskite phase was obtained for samples liquid phase sintered with high electrical conductivity values.
Yttrium and Nickel Co-Doped BaZrO3 as a Proton-Conducting Electrolyte for Intermediate Temperature Solid Oxide Fuel Cells
Authors: P. Shafi Shahid , Bi Lei , Boulfrad Samir , Traversa Enrico
Published: July 2015

High temperature proton conducting oxides, due to their lower activation energy for proton conduction, can achieve high conductivity at relatively low temperatures (500-700 °C). Though BaZr0.8Y0.2O3-δ (BZY) perovskite exhibits good chemical stability and high bulk conductivity, high grain boundary resistance decreases its total conductivity. This work focuses on substitution of Zr4+ with Ni2+ in the perovskite B-site in a targeted fashion in order to promote the sinterability of BZY. Powder X-ray diffraction analysis showed the formation of single phases for Ba0.8-xY0.2NixO3-δ compositions up to x = 0.04. Scanning electron microscopy (SEM) image analysis demonstrated that densification is promoted by the increasing Ni-content, reaching a fully dense microstructure for Ba0.76Y0.2Ni0.04O3-δ (BZYNi04). An anode supported single cell based on BZYNi04 electrolyte showed superior power performance, achieving 240 and 428 mW cm-2 at 600 and 700 °C, respectively.
Synthesis of Pure La10-XSrxSi6O27-0.5x Apatites Using an Optimized Sol-Gel Process
Authors: Ma Yangzhou , Fenineche Nouredine , Moliere Michel , El-Kedim Omar , Briois Pascal
Published: July 2015

Apatite-type lanthanum silicates draw researcher’s attention due to their good performances as electrolyte materials for IT-SOFC (intermediate temperature solid oxide fuel cells). In this paper we present the synthesis and characterization of Sr-doped La10Si6O27 (LSO) prepared through an optimized water-based sol-gel process. The parameters involved in this process have been investigated to obtain high purity, high crystallinity powders. The mechanisms of the sol-gel reactions that underlie the quality of the sol are discussed. The developed sol gel process allows to obtain pure apatite structures through a calcination step of 2 hours at a temperature as low as 800℃. The resulting materials were characterized by scanning electron microscopy, X-ray diffraction and energy-dispersive X-ray spectroscopy. Ionic conductivities have been measured after sintering at 1500℃ and the effect of the Sr-doping has been investigated. The results show that the ionic conductivity is thermally activated and values lies between 4.5×10-2 and 1×10-6 Scm-1 at 873 K as a function of the composition and powder preparation conditions.
Degradation of Electrical Conductivity in Lanthanum Silicate Oxyapatite
Authors: Ishiyama Tomohiro , Maruyama Hiraku , Kishimoto Haruo , Bagarinao Katherine Develos- , Horita Teruhisa , Yamaji Katsuhiko , Yamazaki Atsushi
Published: July 2015

Degradation of electrical conductivity in lanthanum silicate oxyapatite (La9.33+x
Si6O26+1.5x
) was observed at 600 ~ 1000oC. Small particles were detected on the surface of pellets after electrical conductivity measurements for 100~201 h. These particles were identified as La2SiO5 phase using micro-raman spectroscopy. Lanthanum content in the oxyapatite phase is strongly related to its conductivity, because the excess oxygen is incorporated by charge compensation according to excess lanthanum composition. This study suggests that the decrease in electrical conductivity may be attributed to reduction in electrical charge carriers as a result of the phase degradation of La2SiO5 phase from oxyapatite phase.
Doped Apatites for Novel Solid Oxide Fuel Cell Applications
Authors: Ow Jia Wei Nicholas Earvin , Musso Federico , Bertuzzo Marcus , Alfredsson Maria , Corà Furio
Published: July 2015

The aim of this study is to gain insight into the local coordination of doped Apatites (e.g. La8Y2Ge6O27)using the GULP (General Utility Lattice Program) code. Apatite ceramics are believed to facilitate oxygen conduction by rearranging its local structure in the presence of oxygen excess. By understanding the oxygen conduction mechanism we can design materials with improved functionality.The objectives of this study are twofold: firstly, to investigate the energetics of doping in the Ge apatites and secondly, to further investigate the interstitial-oxide migration pathway and energy barriers involved in the migration. It has been found that isovalent doping with ions of smaller ionic radii than Ge4+, e.g. Si4+and Ti4+, are favourable, as is hypervalent doping on the Sr site, leading to an oxide ion excess in the structure. The excess oxide ion migration pathway takes place via a wheel mechanism with an energy barrier of 0.66 eV. This mechanism is different from the one proposed in Si-based apatites, which is done by a sinusoidal trajectory.
Physical-Chemical Properties of Bi13-XMexMo5O34±δ (Me = Mg, Ca, Sr, Ba) Solid Solutions
Authors: Mikhaylovskaya Zoya , Buyanova Elena , Morozova Maria , Petrova Sofia , Nikolaenko Irina
Published: July 2015

Single phase samples of Bi13-xMexMo5O34±
δ, Me = Mg, Ca, Sr, Ba (0.0 ≤ x ≤ 1.0) series were indexed according to triclinic Bi13Mo5O34.5 structure (if the concentration of the dopant was small) or monoclinic Bi13Mo5O34.5 structure (if the concentration of dopant was large). These ranges are various for different dopants because of ratio difference of ionic radii of the dopants and the Bi ion: rMg+2 << rBi+3; rCa, rSr+2≈ rBi+3; rBa+2> rBi+3 (the values of ionic radii with coordination number = 8 are: rMg+2= 0.89Å, rCa+2= 1.12 Å, rSr+2 = 1.26 Å, rBa+2= 1.42 Å; rBi+3= 1.17 Å. For all substituting metals the increase of dopant concentration results in the rise of symmetry and in stabilization of the monoclinic form at room temperature.
Materials Search of Perovskite Cathode in SOFC by Statistical Analysis
Authors: Hwang Jaekyun , Ando Yasunobu , Watanabe Satoshi
Published: July 2015

We explore critical factors that can explain the oxygen exchange rate of perovskite-oxide cathode in solid oxide fuel cell (SOFC). It has been said that the bulk ionic conductivity is strongly related to the oxygen exchange rate, while the electronic conductivity is not as far as it is high enough. However, we found that the combination of ionic and electronic conductivities shows much stronger correlation than ionic conductivity alone while analyzing experimental data reported in the literature. Materials which have high oxygen exchange rate can be explained by the product of bulk ionic and electronic conductivities while others by the ionic conductivity alone.
Surface Composition and Oxygen Transport Properties of LSCF: From Bulk Ceramics to Devices
Authors: Druce John , Téllez Helena , Ishihara Tatsumi , Kilner John A.
Published: July 2015

Although the oxygen surface exchange reactions are of utmost importance for Solid Oxide Fuel Cells and Solid Oxide Electrolyser operation and performance, these reactions are rather poorly understood. One part of the puzzle is understanding the composition of the surfaces and interfaces participating in the reactions. Ion beam techniques constitute powerful probes of the surface composition, as well as the oxygen transport properties. Here, we use the well-known mixed conducting perovskite LSCF to illustrate how ion beam techniques such as secondary ion mass spectrometry (SIMS) and low energy ion scattering (LEIS) can be used to study fundamental materials properties such as oxygen tracer diffusion and strontium segregation, as well as segregation and impurity migration processes in model electrode structures.
Study of 2R-Cell Equipped with LSC and LSCF Cathodes under Thermic and Redox Cycling
Authors: Coquoz Pierre , Grize Carolina , Ruiz Jesus , Bourradou Anais , Diethelm Stefan , Singh Vaibhav , Ihringer Raphaël
Published: July 2015

The 2R-Cell, developed by Fiaxell Sàrl, provides robustness and reliability upon multiple thermic and redox cycles. In this article we present the results of 2R-Cell tested under thermic and redox cycles. Different cathodes were studied, composite LSC-GDC and LSCF, in terms of electrical performances and resistance to thermic cycles. Degradation due to multiple thermic and redox cycles is reported and discussed. Three composite LSC-GDC cathodes were tested (40, 60 and 75 % GDC). Surprisingly the highest power density was achieved with a cathode containing 75% of GDC in the composite layer. The cell provided a current density of 1060 [mA/cm2] at 0.8 V and 780°C, before thermic cycling. This cell underwent 40 thermic cycles with an average power loss of 0.7 % per cycle and providing a power of 621 [mW/cm2] at the end. A LSCF cathode equipped 2R-Cell, tested by EPFL our partner in an EU project (Roxsolidcell), was subjected to 20 thermic cycles and 20 redox cycles. With this cathode material the average ASR increase was 0.3% per thermic cycle and 0.5 % per redox cycle. SEM pictures of the tested cells after thermic cycles are presented and discussed.
Influence of Hetero Grain Boundaries on Oxygen Exchange Activity: Investigation of Two-Phase (La,Sr)CoO3-δ / (La,Sr)2CoO4+δ Cathode Materials
Authors: Stämmler Sebastian , Merkle Rotraut , Stuhlhofer Benjamin , Logvenov Gennady , Maier Joachim
Published: July 2015

Several recent publications have claimed that the oxygen exchange surface reaction is accelerated at hetero grain boundaries betwen La1-xSrxCoO3-
d and (La1-ySry)2CoO4+
d. To investigate this effects in a greater detail, PLD films with a high density of such hetero grain boundaries are prepared from a two-phase target, and characteristic crystal morphologies are observed. The issue of preferential Sr accumulation in the (La1-ySry)2CoO4+
d Ruddlesden-Popper phase is exemplarily quantified for two-phase powder samples based on X-ray diffraction. The implications of this uneven Sr distribution (occurring similarly in the two-phase films) for the analysis of the oxygen exchange kinetics and quantification of the specific hetero grain boundary effect are discussed