Thin Films Of YSZ Research Articles

Carbon tolerance of Ni–Cu and Ni–Cu/YSZ sub-μm sized SOFC thin film model systems

Thin films of YSZ, unsupported Ni–Cu 1:1 alloy phases and YSZ-supported Ni–Cu 1:1 alloy solutions have been reproducibly prepared by magnetron sputter deposition on Si wafers and NaCl(001) single crystal facets at two selected substrate temperatures of 298K and 873K. Subsequently, the layer properties of the resulting sub-μm thick thin films as well as the tendency towards carbon deposition following treatment in pure methane at 1073K has been tested comparatively. Well-crystallized structures of cubic YSZ, cubic NiCu and cubic NiCu/YSZ have been obtained following deposition at 873K on both substrates. Carbon is deposited on all samples following the trend Ni–Cu (1:1)=Ni–Cu (1:1)/YSZ>pure YSZ, indicating that at least the 1:1 composition of layered Ni–Cu alloy phases is not able to suppress the carbon deposition completely, rendering it unfavorable for usage as anode component in sub-μm sized fuel cells. It is shown that surfaces with a high Cu/Ni ratio nevertheless prohibit any carbon deposition.

Dynamics of interacting oxygen ions in yttria stabilized zirconia: bulk material and nanometer thin films

The oxygen vacancy dynamics in bulk yttria-stabilized zirconia studied experimentally by conductivity relaxation and quasielastic light scattering had shown anomalous properties that had been attributed to the many-ion effects originating from ion-ion interaction. In the explanation of the anomalous properties given more than ten years ago, some predictions including the actual value of the energy barrier opposing oxygen ion hop have been made but remain unverified. Since then, many molecular dynamics simulations on oxygen vacancy dynamics in bulk YSZ have been published. Moreover, oxygen vacancy dynamics in nanometer thin films of YSZ fabricated in various fashion have been measured by conductivity relaxation as well as studied by computer simulations. This rich collection of new experimental and computer simulations results provide fertile ground for testing the predictions made before. The tests are made and the results are positive. The advance lends considerable support of the previously published explanation of oxygen vacancy dynamics in bulk YSZ. We pointed out that ion dynamics similar to YSZ are found in other ionic conductors, and the explanation for YSZ given here also works there.

Preparation of NiO-YSZ Substrate for Electrophoretic Deposition of Thin YSZ Film

In this report, a strategic approach for preparation of dense 8YSZ electrolyte layer on porous NiO-YSZ substrate was proposed. Porosity in the substrate was introduced by mixing corn starch with the starting NiO-YSZ powder. By varying the content of corn starch, porosity and sintering shrinkage of the sintered substrates were studied. The porous substrates were deposited with an electrolyte layer using the Electrophoretic Deposition (EPD) technique. The difference in total sintering shrinkage between the substrate and that of YSZ electrolyte layer was found to be the major cause of cracks and pores in the electrolyte films. Finally, by optimizing the preparation conditions of the porous NiO-YSZ substrates, a dense YSZ film as thin as 2μm was successfully fabricated.

Nanostructured YSZ Thin Film for Application as Electrolyte in an Electrode Supported SOFC

The development of solid oxide fuel cell with thin film concepts for an electrode supported design based on the yttria-stabilized zirconia has demonstrated favourable results due to its high chemistry stability in oxidization and environment reduction. The spray pyrolysis process was investigated in order to obtain dense thin films of YSZ on different substrates. The precursor solution was obtained by zirconium and yttrium salt dissolutions in a mixture of water and glycerine in several ratios to study the solvent influence. The substrate was initially heated at 600 °C and during the deposition it ranged from 260-350°C, finishing at a fast increase in temperature of 600°C. The heat treatment was carried out in four different temperatures: 700 °C, 750 °C, 800 °C, and 900 °. The precursors were characterized by thermal analysis. The microstructures of the films were studied using scanning electron microscopy and X-ray diffraction. The results obtained showed that the films obtained were crystalline before the heat treatment process and have shown ionic conductivity above 800°C.

Elaboration of Yttria-Stabilized Zirconia Films on Porous Substrates

The development of solid oxide fuel cell has shown that the thin film concept for the electrode supported designs, based on the yttria-stabilized zirconia, is more promising than the research of new electrolyte materials. In this work, the spray pyrolysis process was investigated in order to obtain dense thin films of YSZ on porous ceramic substrates. High porosity LSM, a typical material of SOFC cathodes, was used as substrate. The precursor solution was obtained by zirconium and yttrium salts dissolved in a mixture of ethanol and propylene glycol, with volume ratio 1:1. The substrate was heated and maintained at a constant temperature (280°C, 340°C or 560°C). The as-obtained films were heat treated in a temperature of 700°C, aiming to obtain yttria-stabilized-zirconia films from the amorphous film. The morphology and microstructure of the films were characterized by scanning electron microscopy and X-ray diffraction.

Polarization of Anode-Supported Solid Oxide Fuel Cells Studied by Pt Reference Electrode in Symmetric and Asymmetric Configurations

A symmetric three-electrode configuration was applied to an anode-supported solid oxide fuel cell to study electrode polarization and the results were compared with those obtained via an asymmetric reference configuration. In this study, Ni/YSZ was used as the anode, LSM/YSZ as the cathode, Pt as the reference electrode, and thin YSZ film as the electrolyte. The cells were polarized potentiostatically at - 0.2 V, - 0.4 V, - 0.6 V and - 0.8 V with respect to open circuit voltage (OCV) and the potential changes of the anode and the cathode were measured via reference electrode simultaneously. The data from both symmetric and asymmetric configurations indicated cathode overpotentials was much larger than that observed on the anode. The cathode overpotentials decreased with increasing temperature. At low polarizations, cell overpotentials were disproportionately cathodic but the difference between anode and cathode polarization decreased with increasing polarization. The relative contribution of anodic overpotentials compared to cathodic was also observed to increase with increasing cell temperature.

Electrophoretic Deposition of YSZ Electrolyte on Porous NiO-YSZ Substrate for Solid Oxide Fuel Cells

: In this study a thin dense YSZ film has been fabricated from stable non-aqueous suspensions by Electrophoretic Deposition (EPD) method on a porous pre-sintered NiO-YSZ substrate. Thin film of YSZ and NiO-YSZ composite were used as electrolyte and anode, respectively, in SOFCs that should have certain characteristics. Process parameters like porosity, pre-sintering temperature, voltage and time of deposition have been considered and optimized for obtaining a controlled thickness. After depositing a conductive layer, EPD has been performed on NiO-YSZ composites. These layers were sintered and a crack-free dense thin film of 8 mol % YSZ was obtained on porous NiO-YSZ anode. The interface and adhesion between the two layers was investigated by Scanning Electron Microscope and microstructural observations.

Polarization measurements of anode-supported solid oxide fuel cells studied by incorporation of a reference electrode

A three-electrode system configuration was applied to an anode-supported solid oxide fuel cell where the anode to cathode surface area ratio was ∼7.9, and Ni/YSZ was used as the anode, LSM as the cathode, Pt as the reference electrode, and thin YSZ film as the electrolyte. The cell was polarized potentiostatically at −0.2, −0.4, −0.6 and −0.8 V versus open circuit voltage (OCV) and the potential change versus a reference electrode were recorded to ascertain the relative electrode polarization contributions. The results of these studies suggested that, while the anode contributions to cell polarization were less significant than that observed for the cathode, they were not negligible. Furthermore, the disparity in the relative electrode polarization contribution was observed to decrease with increasing temperature and polarization. Electrode polarization studies suggested that cathodic overvoltage decreased remarkably with increasing temperature whereas anodic overvoltage increased slightly with increasing temperature. Electrode kinetic parameters were extracted from these polarization experiments and the implications of these parameters to cell performance were discussed. Lastly, electrochemical impedance spectroscopy (EIS) data was presented to further elucidate the relative contributions of the anode and cathode impedances on button cell performance.

High-performance cathode-supported SOFC with perovskite anode operating in weakly humidified hydrogen and methane

A high-performance, cathode-supported solid oxide fuel cell (SOFC), suitable for operating in weakly humidified hydrogen and methane, has been developed. The SOFC is essentially made up of a YSZ–LSM composite supporting cathode, a thin YSZ film electrolyte, and a GDC-impregnated La0.75Sr0.25Cr0.5Mn0.5O3 (LSCM) anode. A gas-tight thin YSZ film (27 μm) was formed during the co-sintering of the cathode/electrolyte bilayer at 1200°C. The cathode-supported SOFC developed in this study showed encouraging performance with maximum power density of 0.182, 0.419, 0.628 and 0.818 W/cm2 in air/3% H2O–97% H2 (and 0.06, 0.158, 0.221 and 0.352 W/cm2 in air/3% H2O–97% CH4) at 750, 800, 850 and 900°C, respectively. Such performance is close to that of the cathode-supported cell (0.42 W/cm2 versus 0.455 W/cm2 in humidified H2 at 800°C) developed by Yamahara et al.[1] [DOI: 10.1016/j.ssi.2004.09.023] with a Co-infiltrated supporting LSM-YSZ cathode, an (Sc2O3)0.1(Y2O3)0.01(ZrO2)0.89 (SYSZ) electrolyte of 15 μm thickness and an SYSZ/Ni anode, indicating that the performance of the GDC-impregnated LSCM anode is comparable to that made of Ni cermet while stable in weakly humidified methane fuel.

High performance cathode-supported SOFC with perovskite anode operating in weakly humidified hydrogen and methane

A high performance cathode-supported solid oxide fuel cell (SOFC), suitable for operating in weakly humidified hydrogen and methane, has been developed. The SOFC is essentially made up by a YSZ/LSM composite supporting cathode, a thin YSZ film electrolyte, and a GDC-impregnated La 0.75Sr 0.25Cr 0.5Mn 0.5O 3 (LSCM) anode. A gas tight thin YSZ film (∼27 μm) was formed during the co-sintering of cathode/electrolyte bi-layer at 1200 °C. The cathode-supported SOFC developed in this study showed encouraging performance with maximum power density of 0.182, 0.419, 0.628 and 0.818 W cm −2 in air/3% H 2O–97% H 2 (and 0.06, 0.158, 0.221 and 0.352 W cm −2 in air/3% H 2O–97% CH 4) at 750, 800, 850 and 900 °C, respectively. Such performance is close to that of the cathode-supported cell (0.42 W cm −2 vs. 0.455 W cm −2 in humidified H 2 at 800 °C) developed by Yamahara et al. [Solid State Ionics 176 (2005) 451–456] with a Co-infiltrated supporting LSM-YSZ cathode, a (Sc 2O 3) 0.1(Y 2O 3) 0.01(ZrO 2) 0.89 (SYSZ) electrolyte of 15 μm in thickness and a SYSZ/Ni anode, indicating that the performance of the GDC-impregnated LSCM anode is comparable to that made of Ni cermet while stable in weakly humidified methane fuel.

졸-겔법을 이용한 고체산화물연료전지의 전해질 박막 제조 및 가스 투과도

In this study, thin electrolyte layer was prepared by 8YSZ (8 mol% Yttria-Stabilized Zirconia) slurry dip and sol coating onto the porous anode support in order to reduce ohmic resistance. 8YSZ polymeric sol was prepared from inorganic salt of nitrate and XRF results of xerogel powder exhibited similar results (99.2±1 wt%) compared with standard sample (TZ-8YS, Tosoh Co.). The dense and thin YSZ film with 1 μm thickness was synthesized by coating of 0.7 M YSZ sol followed by heat-treatment at 600℃ for 1 h. Thin film electrolyte sintered at 1400℃ showed no gas leakage at the differential pressure condition of 3 atm.

Yttria-doped zirconia thin films deposited by atomic layer deposition ALD: a structural, morphological and electrical characterisation

The recent development of solid oxide fuel cells is focused on a significant reduction in their operating temperature, from 850–1000 to 550–750 °C. One way to reach this goal is to reduce the thickness of the commonly used electrolyte, yttria stabilised zirconia, YSZ. Thin films of YSZ were prepared on soda lime glass, SnO 2-coated glass, strontium-doped lanthanum manganite and Ni-YSZ cermet by atomic layer deposition. This technique is a sequentially controlled chemical vapour deposition technique, allowing the formation of the deposit monolayer by monolayer. The stoichiometry and morphology of the films were analysed by scanning electron microscopy/energy dispersive analysis of X-ray and wavelength dispersion spectroscopy. Thin (about 1–3 μm), dense and homogeneous layers were obtained with a doping content of Y 2O 3 of 8.5 mol%. The structural characterisation was realised by X-ray diffraction and Raman spectroscopy. It was shown by both methods that the cubic structure is predominant. Impedance spectroscopy at room temperature allowed to determine some characteristic parameters of YSZ material: capacitance and dielectric constant.

Chemical spray deposition of YSZ and GCO solid electrolyte films

The chemical deposition of YSZ and GCO solid electrolyte films by spraying of precursor solutions onto heated substrates was investigated using ultrasonic atomisation. Various precursors (chlorides, acetylacetonates and alcoxides of the corresponding metals) and solvents (ethanol, diethylene glycol, diethylene glycol monobutyl ether, diethylene glycol monobutyl ether acetate and triethylene glycol monobutyl ether) were tested. The experimental results are presented and the mechanism of the film formation is discussed. It is shown that dense thin films of YSZ and GCO are formed from liquid droplets spreading on the substrate surface. A novel technology for thin film electrolyte solid oxide fuel cells which uses etched metallic meshes as an electrolyte support and current collector is demonstrated.

Preparation of YSZ Thin Film on Porous Electrode of SOFC

AbstractPorous electrode substrate of La0.7Sr0.2MnO3 was used as the support for the deposition of YSZ thin films. The porosity of the electrode substrate was controlled by sintering temperature and particle size of powders. Thin films of YSZ were fabricated on the electrode by sol-gel method. The YSZ film fabricated by 10-fold coating with 0.05M YSZ sol containing TEA was continuous and crack-free one of 5 mm in thickness. However, hydrogen permeation measurement showed that there was a very small leakage of hydrogen in the fabricated film. In addition to sol-gel method, another technique such as EVD should be employed to make the film completely gas-tight.

Performance of a Tubular SOFC With Thin YSZ Film at Medium Temperatures

Performance of a Tubular SOFC With Thin YSZ Film at Medium Temperatures

Thin film fabrication of stabilized zirconia for solid oxide fuel cells

Thin or thick films of YSZ were fabricated by plasma spraying, slip casting, slurry coating, spray pyrolysis, and RF-ion plating methods. A porous electrode substrate of Ni/YSZ cermet anode or La 0.06 Sr 0.4 MnO 3 cathode was used as a support for YSZ film fabrication. Current-voltage characteristic of hydrogen-oxygen fuel cell with a slurry coated or a slip casted YSZ film was excellent, because these films were dense. The plasma spraying method was most suitable for quick fabrication of cell stacks.