Yttrium-doped Barium Zirconate Research Articles

Fabrication of yttria-doped barium zirconate electrolyte with sub-micrometer thickness via low temperature viscous flow sintering

Viscous flow sintering strategy has been adopted to obtain dense sub-micrometer thin yttria-doped barium zirconate (BZY) films fabricated via chemical solution deposition method. Viscous flow sintering was carried out at the temperatures between 475 and 575°C for 24h to allow densification in amorphous phase so as to avoid coarsening. The sintered films were finally heat treated at 950°C for 2h to eliminate the pores generated due to the removal of residual carbon which remains after low temperature viscous flow sintering. Dense, single-phase perovskite BZY films with thickness between 325 and 375nm were obtained without the presence of barium carbonate, which is a common issue associated with soft chemical synthesis of BZY. In addition to this, this process does not require sintering aid.

Conductivity recovery by redox cycling of yttrium doped barium zirconate proton conductors and exsolution of Ni-based sintering additives

Abstract Owing to their high stability and good bulk proton conductivity yttrium doped barium zirconate-based materials are considered as potential electrolytes for protonic ceramic fuel cell applications. Nonetheless, their refractory nature leads to problematic densification that can necessitate the addition of sintering additives. While these additives assist processing, undesirable, strong, negative impacts on proton conductivity have been regularly reported. The current work assesses the potential sintering additives NiO, BaNiOx and BaY2NiO5 and their influence on subsequent electrochemical properties of BaZr0.85Y0.15O3-δ. All sintering additives allow dense electrolyte materials (>95%) to be formed at temperatures below 1450 °C, with enhanced grain growth; with the largest grain growth being offered by the BaNiOx additive. Degradation in overall electrical performances is shown to be bulk related, corresponding to large reductions in bulk conductivity up to two orders of magnitude, whilst grain boundary conductivities are less affected. Most importantly, the current article demonstrates that these high depletions in bulk proton conductivity can be effectively inverted by redox cycling in relatively mild conditions (750 °C, cycling from N2 to H2 and back to N2), opening the way to improve processing of these materials whilst maintaining high levels of proton conductivity.

Probing Grain-Boundary Chemistry and Electronic Structure in Proton-Conducting Oxides by Atom Probe Tomography.

A laser-assisted atom-probe-tomographic (LAAPT) method has been developed and applied to measure and characterize the three-dimensional atomic and electronic nanostructure at an yttrium-doped barium zirconate (BaZr0.9Y0.1O3-δ, BZY10) grain boundary. Proton-conducting perovskites, such as BZY10, are attracting intense interest for a variety of energy conversion applications. However, their implementation has been hindered, in part, because of high grain-boundary (GB) resistance that is attributed to a positive GB space-charge layer (SCL). In this study, LAAPT is used to analyze BZY10 GB chemistry in three dimensions with subnanometer resolution. From this analysis, maps of the charge density and electrostatic potential arising at the GBs are derived, revealing for the first time direct chemical evidence that a positive SCL indeed exists at these GBs. These maps reveal new insights on the inhomogeneity of the SCL region and produce an average GB potential barrier of approximately 580 mV, agreeing with previous indirect electrochemical measurements.

Electrochemical and Thermal Catalytic Syntheses of Ammonia over Yttrium-Doped Barium Zirconate and Cerate Perovskites Supported Ruthenium Catalysts

To resolve a global serious problem on energy consumption by human, the development of various new processes which a renewable energy and a surplus electric power generated from thermal and nuclear power plants are converted to the energy easy to handle is required. As one possible process, a technological process that electrical energy is convert to a chemical substance, so-called energy carrier, is raised. As a candidate of energy carrier, methylcyclohexane (MCH), ammonia (NH3), hydrogen peroxide (H2O2), formic acid (HCOOH) are considered in recent years. In the present work, we have paid attention to NH3. In other words, it is an electrolysis process to produce NH3 from the nitrogen contained in air and the hydrogen supplied by the electrolysis of water. For this electrochemical synthesis process, H2O or H2 is oxidized to proton at the anode, and proton is transported through the proton conducting electrolyte to the cathode. And then, N2 is reacted with proton and reduced to NH3 at the cathode. The lower the operation temperature, the more effective the electrolysis synthesis process of ammonia from N2 and H2O, compared with a conventional Harber-Bosch process. However, the development of solid electrolyte exhibiting high conductivity at lower temperature and the selection of electrode catalyst materials and electrode design to improve the reaction rate of ammonia synthesis for the cathode are required. Therefore, in this study, we have focused on the Ru based catalyst which is well known to be excellent catalysts for thermal catalytic synthesis of ammonia. Furthermore, Ba-Zr-Y and Ba-Ce-Y perovskite-type oxides exhibiting high proton conductivity have been used as a support material to improve the cell performance for electrochemical ammonia synthesis. Firstly, the Ru/Ba-Zr-Y and/or Ba-Ce-Y perovskites solid catalyst was prepared, and its thermal catalytic property for ammonia synthesis was evaluated using a fixed bed flow reactor. As results of comparison tests, Ru/Ba-Zr-Y catalyst showed higher activity than Ru/Ba-Ce-Y catalyst. Furthermore, it was found that an addition of 10wt% of Y component to BaZrO3 perovskite enhances the catalytic performance significantly. And noted that Ru/Ba-Zr-Y catalyst exhibited higher performance than a conventional Ru-Cs+/MgO catalyst. Based on various characterization, we consider that electron transfer from Ba-Zr-Y perovskite to Ru species enhances the dissociation of N-N bond, leading to the high activity for ammonia synthesis. Additionally, in the present work, we have studied the effect of current loading to the catalyst on the catalytic performance for ammonia synthesis to evaluate the applicability of Ru/Ba-Zr-Y catalyst to an electrode catalyst. Acknowledgments This work was supported by CREST, Japan Science and Technology Agency.

Measurement of Chemical Potential in Bcy Electrolyte with Varying Thickness and Configuration Using Embedded Reference Electrodes

The correlation between internal chemical potential, and durability of anode-supported BCY (yttria-doped barium cerate) electrolyte cells, was investigated as a function of electrolyte thickness and configuration. Internal hydrogen and oxygen chemical potentials were measured using embedded Pt probes. As the electrolyte thickness decreased, the internal chemical potential became dominated by the gases surrounding the cathode, indicating that the thin BCY cell may be vulnerable to water vapor produced at the cathode during operation. BCY cells with BZY (yttria-doped barium zirconate) protecting at the cathode side (bi-layer cells) showed a small chemical potential variation through the electrolyte region close to the electrode side, indicating significant electronic conduction.Constant-current tests were conducted on thin (~ 10 µm) and thick (~ 35 µm) BCY single layer cells, and also on BCY-BZY bi-layer cells, especially under negative voltage conditions. Consistent with the results of the internal chemical-potential measurements, the thin BCY single layer cell showed a significant rate of degradation due to changes in BCY composition in the electrolyte and cathode, while the thick BCY single layer cell showed much better durability, regardless of the sign of cell voltage. The bi-layer cell was stably operated under any severe operating conditions, because of the BZY protecting layer against water vapor’s attack and its significant electronic conduction close to the cathode/electrolyte interface. Thus, the present work shows the effect of BCY electrolyte thickness and configuration on the durability of BCY based cells, in terms of their internal chemical potential.

Atomic Resolution Distortion Analysis of Yttrium-Doped Barium Zirconate

Atomic Resolution Distortion Analysis of Yttrium-Doped Barium Zirconate

Effect of synthesis atmosphere on the proton conductivity of Y-doped barium zirconate solid electrolytes

Yttrium-doped barium zirconate ceramic powders were synthesized by the oxidant peroxide method in air and under controlled atmosphere of nitrogen inside a glove box. The powders were characterized by thermogravimetry, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. After uniaxial cold isostatic pressing, green pellets were sintered at 1600°C for 4h. The electrical conductivity behavior was accessed by electrochemical impedance spectroscopy. The results show that specimens synthesized under controlled atmosphere achieved higher electrical conductivity, two orders of magnitude higher than specimens prepared in laboratory air. The enhancement in electrochemical properties and increase in sintering ability is attributed to the less carbonate contamination as a result lower grain boundary density in the samples prepared under controlled atmosphere.

Mechanical degradation under hydrogen of yttrium doped barium zirconate electrolyte material prepared with NiO additive

Recently, a novel process was presented to fabricate dense yttrium-doped barium zirconate electrolytes with high proton conductivity. This process was based on the use of a NiO additive during reactive sintering. We show here that materials made from this process present a fast degradation of mechanical properties when put in hydrogen-rich conditions, while material made from conventional sintering without NiO aid remains intact in the same conditions. The fast degradation of samples made from reactive sintering, leading to sample failure under highly compressive conditions, is due to the reduction of NiO nanoparticles at grain boundaries as shown from structural and chemical analyses using Transmission Electron Microscopy. By the present study, we alert about the potential risk of cell failure due to this mechanical degradation.

Characterization and Performance of Proton Conducting Solid Oxide Fuel Cells Manufactured Using Reactive Spray Deposition Technology

Proton conducting solid oxide fuel cells (p-SOFC) have received attention recently as an alternative to traditional high temperature SOFCs [1]. This new class of p-SOFCs offer the potential to significantly reduce the cost of production due to the opportunity to lower the operating temperature from upwards of 800 °C down to as low as 500 °C. This shift is made possible by a modified class of ion conducting materials such as yttrium doped barium zirconate (BYZ) which has comparable ionic conductivity to yttria-stabilized zirconia at lower temperatures [2]. With a decrease in the operating temperature, it becomes possible to make use of inexpensive materials for cell construction such as stainless steels vs. expensive super alloys. This cost savings is a major driver towards practical commercialization of p-SOFCs. This work seeks to employ a novel flame based technique, Reactive Spray Deposition Technology (RSDT) [3], in manufacturing of a complete p-SOFC on a metal support. This technique involves dissolving organometallic precursor compounds (typically ethlyhexanoate ligands) into combustible solvents. The mixture is sprayed from an atomizing nozzle in an open atmosphere and ignited. The resulting heat of combustion due to the solvent is used to decompose the dissolved compounds and produce thin films via gas to particle conversion. The use of the flame eliminates the need for separate, costly sintering steps generally needed in traditional manufacturing processes. Secondary nozzles can be utilized to introduce different support and binder materials resulting in a single-step manufacturing process for the anode, electrolyte, and cathode of the p-SOFC. The current work focuses on the production and initial characterization of a p-SOFC using a Ni-BYZ anode, BYZ electrolyte, and lanthanum strontium cobalt ferrite (LSCF) cathode on a porous metal support. The deposited materials are characterized using SEM, STEM, and XRD techniques. Initial button cell performance is also reported.

Proton-conducting Micro-solid Oxide Fuel Cells with Improved Cathode Reactions by a Nanoscale Thin Film Gadolinium-doped Ceria Interlayer.

An 8 nm-thick gadolinium-doped ceria (GDC) layer was inserted as a cathodic interlayer between the nanoscale proton-conducting yttrium-doped barium zirconate (BZY) electrolyte and the porous platinum cathode of a micro-solid oxide fuel cell (μ-SOFC), which has effectively improved the cathode reaction kinetics and rendered high cell power density. The addition of the GDC interlayer significantly reduced the cathodic activation loss and increased the peak power density of the μ-SOFC by 33% at 400 °C. The peak power density reached 445 mW/cm2 at 425 °C, which is the highest among the reported μ-SOFCs using proton-conducting electrolytes. The impressive performance was attributed to the mixed protonic and oxygen ionic conducting properties of the nano-granular GDC, and also to the high densities of grain boundaries and lattice defects in GDC interlayer that favored the oxygen incorporation and transportation during the oxygen reduction reaction (ORR) and the water evolution reaction at cathode.

Membrane polarization in mixed-conducting ceramic fuel cells and electrolyzers

This paper focuses on modeling membrane-polarization processes within mixed-conducting electrolyte membranes. Because a complete set of thermodynamic and transport properties is available, the electrolyte material used for the study is a yttrium-doped barium zirconate (BaZr0.9 Y0.1 O3−δ, BZY10). Unlike Polymer Electrolyte Fuel Cells (PEMFC) and Solid-Oxide Fuel Cells (SOFC), the open-circuit voltage cannot be evaluated using gas-phase compositions alone. Using a Nernst-Planck-Poisson (NPP) model, an important aspect of the present paper is to develop the theory needed to evaluate open-circuit potential. Focusing on the mixed-conducting membrane alone, the present model neglects all activation and concentration overpotentials. The model is exercised in both fuel-cell and electrolyzer modes, revealing significantly different polarization behaviors. The model-based results show how the membrane polarization depends upon operating conditions, including temperature and gas-phase compositions.

A high temperature reduction cleaning (HTRC) process: a novel method for conductivity recovery of yttrium-doped barium zirconate electrolytes

A novel high temperature reduction cleaning (HTRC) process to recover the electrical conductivity of Y-doped barium zirconate electrolytes from Ni contamination.

Proton-conducting solid oxide fuel cells with yttrium-doped barium zirconate electrolyte films sintered at reduced temperatures

Barium zirconate-based high-temperature proton conductors have not been widely used as electrolytes for solid oxide fuel cells (SOFCs) due to the poor sintering activity and the difficulty in preparing dense and highly conductive electrolyte films. In this work, thin BaZr0.8Y0.2O3-δ (BZY) proton-conducting electrolyte films were prepared by a conventional dry-pressing method followed by sintering in flowing oxygen. BZY films got fully dense after sintered at a low temperature of 1350 °C for 5 h. Single cells with BZY electrolyte films prepared at various temperatures were assembled and tested. The influence of sintering temperature on the morphology of BZY films and electrochemical performances of single cells was investigated. Besides, the open circuit voltages of the single cells as well as those previously reported BZY-based SOFCs were also discussed.

Cell Performance of Anode-Supported BaZr0.85Y0.15O3-δ/Carbonate Composite Electrolyte at Intermediate Temperature

Recently, proton-conducting based-protonic ceramic fuel cells (PCFCs) have received great attentions as sustainable power generators at the intermediate temperature, because of their higher ionic conductivity with lower activation energy as compared to the oxygen-ion-conducting electrolytes based solid oxide fuel cells (SOFCs). Among several perovskite-type proton conducting oxides, yttrium-doped BaZrO3 (BZY) have exhibited considerable bulk proton conductivity with a high chemical resistance against CO2 and H2O in the intermediate temperature range. However, the manufacturing of porous electrode-supported dense BZY electrolyte cells virtually needs awfully difficult processes by the current SOFC technology due to its poor sinterability. Furthermore, high sintering temperature results in decreasing the proton conductivity of BZY with the BaO sublimation and low-conducting Y2O3-like phase formation. In addition, the BZY materials are still required to improve proton conductivity under the PCFC operating condition. To achieve these goals, we have designed two-phase composite electrolytes consisting of a BZY matrix phase and a binary eutectic carbonate (Li–0.5Na)2CO3 phase in previous works. The conductivity of the composite electrolytes is higher than that of the BZY under the PCFC operating condition. Moreover, dense BZY composite electrolytes are fabricated with a carbonate phase at a remarkably low sintering temperature of 670 °C. Hence, in this work, anode-supported BZY/carbonate electrolyte cells are fabricated by the co-pressing technique with the Ni-cermet anode and as lithiated NiO cathode to confirm this composite electrolyte concept and then co-sintered at 600°C for 1 h. For the physicochemical and electrochemical characterizations, the anode-supported composite PCFCs are investigated by various analysis tools such as XRD, SEM, electrochemical polarization, and impedance spectroscopy. [1] K.D. Kreuer, Annu. Rev. Mater. Res. 33 (2003) 333–359. [2] E. Fabbri, D. Pergolesi, E. Traversa, Chem. Soc. Rev. 39 (2010) 4355-4369. [3] E. Fabbri, L. Bi, D. Pergolesi, E. Traversa, Adv. Mater. 18 (2012) 195-208. [4] T. Schober, H.G. Bohn, Solid State Ionics 127 (2000) 351–360. [5] K.-Y. Park, T.-H. Lee, J.-T. Kim, N. Lee, Y. Seo, S.-J Song, J.-Y. Park, J. Alloys Comp. 585 (2014) 103–110. Keywords: Protonic ceramic fuel cell (PCFC), Composite electrolyte, Yttrium-doped barium zirconate (BZY), Carbonate, Performance. * Corresponding authors: jyoung@sejong.ac.kr (J.-Y. Park).

Shape Forming of Ceramic Tubes for Electrochemical Reactors by Gel-Casting Method

Three-dimensional structures are required as electrodes to increase the space time yield of electrochemical reactors when the reactions take place at low current densities. However, a tubular arrangement is necessary in some cases even in the industrial practice. Tubular Electrochemical Reactors (TERs) consist of a dense co-ionic ceramic membrane and two porous electrodes [1,2]. Gel-casting is a promising method of producing tailor-made dimensions of electrolyte and/or electrode tubes for the needs of the above reactors. The basic principle of gel-casting concerns a combination of a solvent, a dispersant, organic monomers and low particle sized ceramic powders to form a high-solids-content, fluid slurry. The slurry is poured under conditions into a casting mold where by an initiator and a catalyst the organic monomers polymerize to form a 3-D polymer network of a solid gel in the shape of the mold. In particular, an aqueous solution of water soluble monomer acrylamide (AM) and cross-linker methylene–bis-acrylamide (MBAM) in appropriate ratio was prepared. Darvan C was used as dispersant and added to the AM and MBAM solution. Subsequently, the ceramic powder was added (i.e 50-80 wt%) and the system was mixed thoroughly to a stable slurry. Finally initiator and catalyst were added to the slurry, respectively ammonium persulfate (APS) and tetra methyl ethylene diamine (TEMED)/g of slurry. The casting slurry is poured into molds of various shapes to form within minutes a gelled green tubular body. Prior any further heating treatment the green bodies may subject to machining i.e cutting and drilling. All volatiles are removed by a heating treatment up to 6000C. Calcination at higher temperatures was applied in order to introduce mechanical strength to the shaped structures through controlled sintering [3]. The sintering temperature is totally depended on the composition of the ceramic powder. Major crucial factors in the overall success of the process are particle size distribution of the ceramic powder, drying conditions, slurry rheology, mold features and sintering parameters. In this study, ceramic powders of an oxygen ion conductor such as apatite-type lanthanum silicates (ATLS) and a proton conductor such as yttrium-doped barium zirconate (BZY) where prepared, optimized and used in gel-gasting methods. They are considered promising electrolytes for intermediate temperature (IT-SOFCs) solid oxide fuel cells. ATLS have attracted interest as promising electrolytes due to their thermodynamic stability, robustness (as ceramics) and their ability to maintain distorted crystal structure by doping but more important due to their high oxide ion conductivity at intermediate temperatures. Additionally they exhibit satisfactory refractoriness with high ionic but low electronic conductivity, low cost and good availability of raw materials [4,5]. On the other hand BZY proton conducting ceramics are regarded as promising electrolyte materials for low temperature proton conducting solid oxide fuel cells due to their higher ionic conductivities and lower activation energy as compared to conventional oxygen-ion conducting electrolytes [6-8]. The above materials were synthesized from various routes, providing thus singled-phased structures and a suitable particle sized distribution for their use in the shape-forming with gel-casting. Powders are verified by XRD, SEM and particle size laser distribution analysis. In addition, rheological measurements were performed at the slurries in order to evaluate the suitable viscosity for a successful shape-forming casting. Different sintering protocols were applied. The porosity of the produced tubes was evaluated by Archimedes method while the microstructure was studied by SEM.

Performance of Protonic Ceramic Fuel Cell with Thin Film Yttrium Doped Barium Zirconate Electrolyte

Perovskite protonic ceramics, or proton-conducting oxides, have attracted much attention in recent decades as alternative electrolytes for conventional solid oxide fuel cells (SOFCs). Protonic ceramics have higher ionic conductivity and lower activation energy in SOFCs’ low operating temperature region (under 600°C) than oxide-ion-conducting oxides. Recently, many attempts have been made to enhance fuel cell performance by adopting thin-film protonic ceramics as electrolytes. In this work, anode-supported thin-film protonic ceramic fuel cells (PCFCs) were fabricated with thin-film yttrium-doped barium zirconate (BZY, BaZr0.85Y0.15O3-δ), which is one of the best-performing protonic ceramics with high bulk ion conductivity and good chemical stability. However, this material possesses poor sinterability, resulting in severe grain separation and a dramatic increase in ohmic overpotential from slow ion transport. In this work, we have applied novel multi-step annealing processes to achieve the densification of the BZY electrolytes, good adhesion between layers, and effective grain growth of the supporting composites. The NiO-BZY composite anode support was fabricated by tape casting and the BZY electrolyte was deposited by pulsed laser deposition (PLD) with a thickness of 2 μm. A perovskite cathode material of La0.6Sr0.4Co3-δ (LSC) was formed porously by PLD with a thickness of 2 μm. The microstructures of the fabricated PCFCs were analyzed using scanning electron microscopy (SEM). The electrochemical performance in terms of current–voltage characteristics was obtained, and the maximum power output of 320‒530 mW/cm2 was measured at 450‒600°C. The alternating current (AC) impedance data were collected under DC bias conditions at each operating temperature and analyzed to determine the resistive factors for the power outputs.

Low Temperature Synthesis of Sub-micrometer Yttria-doped Barium Zirconate Thin Films by Modified Chemical Solution Deposition Technique

Presently research on proton conducting ceramic fuel cell (PCFC) has gained momentum for its low temperature (400 - 600°C) operation; one among the major governing factors for the successful low temperature operation is high ionic conductivity of electrolyte at low temperature. The state of the art protonic ceramic electrolytes are yttria doped barium cerate (BCY) and yttria doped barium zirconia (BZY). Although BCY shows very high protonic conductivity, it shows poor chemical stability in CO2-containing atmosphere. On the other hand, BZY has good chemical stability, but it has little lower protonic conductivity (1 x 10-2 S/cm at 450°C); however, it is sufficient for fuel cell operation. Fabrication of BZY components requires high temperature heat treatment. The major impediments to the fabrication of BZY electrolyte are deviation of stoichiometry due to Ba evaporation at high sintering temperature and the presence of barium carbonate (BaCO3) as impurity; these two factors drastically reduce conductivity of BZY. As per the literature report, sintering temperature for BZY is not less than 1400°C with long sintering time of minimum 5 hrs. This sintering temperature has been achieved with the help of sintering aids such as copper oxide, zinc oxide, etc. The presence of sintering aid also hampers the conductivity of BZY because of the second phase formation and/or segregation of sintering aid at the grain boundaries, thereby leading to low total protonic conductivity. In order to deal with these major issues, in the present research work we have demonstrated a fabrication procedure based on modified chemical solution deposition (CSD) technique of BZY thin film and low temperature sintering strategy without any sintering aid. Thin film reduces the ohmic resistance to the flow of ions in electrolyte, thereby enhancing the performance of PCFC. We have developed an acetate-based solution for thin film fabrication. The solution possesses good wettability to slicon nitride (Si3N4) substrate, thereby eliminating the issue of delamination. Drying control chemical agent (DCCA) was added to the solution in order to prevent crack formation during shrinkage of the film upon heat treatment. The solution is stable for more than three months, as evidenced by Fourier transform infrared spectroscopy (FTIR). The green film was formed on the substrate by spin coating. Subsequently, it was heat treated and sintered at 800°C for 2 hrs with special heat treatment schedule. The special heat treatment strategy involved sintering of BZY film in the amorphous stage due to delayed crystallization. The crystallization was delayed because of slower kinetics of pyrolysis as compared to the heating rate. Following this method, a dense and crack free sintered film was produced; no delamination from the substrate was observed. As per x-ray diffraction profile, the film was phase pure pervskite material without any trace of BaCO3. The novelty of this process lies in the lowest sintering temperature ever reported along with phase pure perovskite BZY. This process also eliminates the detrimental issues such as Ba evaporation and presence of second phase. The method is cost effective and requires less time. Therefore, this thin film fabrication procedure can be promising technique for commercial production of PCFC. Figure 1

Multi-Layered Thin Film Y:BaZrO3 Electrolytes for Anode-Supported Protonic Ceramic Fuel Cells

Acceptor-doped barium zirconate electrolytes, represented as yttrium-doped barium zirconate (Y:BaZrO3 or BZY), are expected to allow ceramic fuel cells to be operated at intermediate temperatures in the range below 600 °C. This is because BZY conducts protons and exhibits a relatively high ionic conductivity with relatively small activation energy, especially compared to ceramics that conduct oxide ions, including yttria-stabilized zirconia (YSZ) and gadolinia-doped ceria (GDC). The bulk conductivity of BZY is greater than that of YSZ by about one order at 600 °C and by two orders at 400 °C and, unlike cerate-based materials, BZY was found to exhibit good phase stability (1). Thus, there have been numerous efforts to develop BZY-based protonic ceramic fuel cells (BZY-PCFCs). Although several studies have reported BZY-PCFCs to perform well, with outputs of 140 mW/cm2 and 180 mW/cm2 in the intermediate temperature regime at 400 °C (2) and 450 °C (3), respectively, both of these were achieved in the form of freestanding nanoscale membranes. For practical production and use, however, fabrication of the BZY electrolyte in anode-supported stacks would be more desirable. Yet, the performance of anode-supported BZY-PCFCs is not yet as good as that of solid-oxide fuel cells. To our knowledge, 170 W/cm2 is the greatest power output achieved with BZY-based fuel cells at 600 °C (4). An attempt to adopt a thin BZY electrolyte (4μm thickness) in anode-supported PCFCs has produced a power output of merely 110 W/cm2 at 600 °C (5), attributed to the prevalence of a relatively large ohmic resistance, which implies the presence of structural defects such as poor grain adhesion (5). After performing a series of experiments, we realized that the adoption of multiple anode support layers with multi-step sintering promotes the structural and mechanical stability of thin film BZY electrolytes. As a result, the power output has exceeded 700 mW/cm2 at 600 °C with an open circuit voltage over 1 V. At this presentation, we will share our recent experimental results and discuss the cell performance in relation with structural characteristics and composition. 1. K. D. Kreuer, Annu. Rev. Mater. Res., 33, 333 (2003). 2. J. H. Shim, J. S. Park, J. An, S. Kang, T. M. Gür, and F. B. Prinz, Chem. Mater., 21(14), 3290 (2009). 3. Y. B. Kim, T. M. Gür, S. Kang, H-J. Jung, R. Sinclair, and F. B. Prinz, Electrochem. Commun., 13(5), 403 (2011). 4. L. Bi , E. Fabbri , Z. Sun, and E. Traversa, Energy Environ. Sci., 4, 409 (2011). 5. D. Pergolesi, E. Fabbri, and E. Traversa, Electrochem . Commun., 12, 977 (2010).

Performance of Protonic Ceramic Fuel Cell with Thin Film Yttrium Doped Barium Zirconate Electrolyte

In this work, anode-supported protonic ceramic fuel cell (PCFC) with thin yttrium doped barium zirconate (BZY) is fabricated using pulsed laser deposition (PLD). For highly dense and thin electrolyte film growth, anode functional layer and anode interlayer are deposited on porous anode support by electrostatic slurry spray deposition and PLD, respectively. As a result, high open circuit voltage of 0.98 V is obtained after anode reduction at 600 oC, indicating that the fabricated BZY electrolyte effectively blocks gas permeation. Electrochemical performance of the PCFC is obtained with peak power densities of 55‒171 mW/cm2 at an operating temperature regime of 450‒600 oC.

Low Temperature Synthesis of Sub-micrometer Yttria-doped Barium Zirconate Thin Films by Modified Chemical Solution Deposition Technique

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.