“…In this regard, the increase in the preferential orientation of film will enhance the overall ionic conductivity by reducing the grain boundary resistance 71 . Similar behavior was observed in the various literature reported for the trivalent doped cerium oxide thin film 64 , 72 . Figure 14 Arrhenius plot for a thin film with respect to the substrate temperature.…”
Quest for efficient ion conducting electrolyte thin film operating at intermediate temperature (~600 °C) holds promise for the real-world utilization of solid oxide fuel cells. Here, we report the correlation between mixed as well as preferentially oriented samarium doped cerium oxide electrolyte films fabricated by varying the substrate temperatures (100, 300 and 500 °C) over anode/ quartz by electron beam physical vapor deposition. Pole figure analysis of films deposited at 300 °C demonstrated a preferential (111) orientation in out-off plane direction, while a mixed orientation was observed at 100 and 500 °C. As per extended structural zone model, the growth mechanism of film differs with surface mobility of adatom. Preferential orientation resulted in higher ionic conductivity than the films with mixed orientation, demonstrating the role of growth on electrochemical properties. The superior ionic conductivity upon preferential orientation arises from the effective reduction of anisotropic nature and grain boundary density in highly oriented thin films in out-of-plane direction, which facilitates the hopping of oxygen ion at a lower activation energy. This unique feature of growing an oriented electrolyte over the anode material opens a new approach to solving the grain boundary limitation and makes it as a promising solution for efficient power generation.
“…In this regard, the increase in the preferential orientation of film will enhance the overall ionic conductivity by reducing the grain boundary resistance 71 . Similar behavior was observed in the various literature reported for the trivalent doped cerium oxide thin film 64 , 72 . Figure 14 Arrhenius plot for a thin film with respect to the substrate temperature.…”
Quest for efficient ion conducting electrolyte thin film operating at intermediate temperature (~600 °C) holds promise for the real-world utilization of solid oxide fuel cells. Here, we report the correlation between mixed as well as preferentially oriented samarium doped cerium oxide electrolyte films fabricated by varying the substrate temperatures (100, 300 and 500 °C) over anode/ quartz by electron beam physical vapor deposition. Pole figure analysis of films deposited at 300 °C demonstrated a preferential (111) orientation in out-off plane direction, while a mixed orientation was observed at 100 and 500 °C. As per extended structural zone model, the growth mechanism of film differs with surface mobility of adatom. Preferential orientation resulted in higher ionic conductivity than the films with mixed orientation, demonstrating the role of growth on electrochemical properties. The superior ionic conductivity upon preferential orientation arises from the effective reduction of anisotropic nature and grain boundary density in highly oriented thin films in out-of-plane direction, which facilitates the hopping of oxygen ion at a lower activation energy. This unique feature of growing an oriented electrolyte over the anode material opens a new approach to solving the grain boundary limitation and makes it as a promising solution for efficient power generation.
“…The use of thin‐film samples with a vertically arrayed microstructure and very low surface roughness helps with an accurate analysis of the penetration distance of the metal impurities and in calculations of the volume ratio of the grain boundaries throughout the sample. [ 26 ]…”
Section: Resultsmentioning
confidence: 99%
“…The procedure of PLD deposition was optimized for CeO 2 thin film and well described in previous research. [ 26,44 ] After the deposition step, all of the samples were annealed in air at 700 °C for 10 h using a tube furnace.…”
Cerium oxide (ceria) is widely used in relation to solid electrolytes in multiple high‐temperature devices, allowing metal components in contact to penetrate into the ceria, especially along the grain boundaries. However, few researchers have concentrated on the migration of metal cations at the operating temperatures (e.g., 600–750 °C) of these devices. Here, the diffusion and solubility of transition metals are investigated through acceptor‐doped ceria grain boundaries as a function of the temperature, pO2, dopant type, and doping concentration. The use of thin‐film samples with high grain boundary density levels and time‐of‐flight secondary ion mass spectrometry with ppb‐level chemical resolution enables an accurate analysis of the concentration profiles of metal species present inside the grain boundaries at such low temperatures. Ni, Fe, and Pt migrate unexpectedly rapidly, and the amounts and types of rare‐earth dopants have a considerable effect on the diffusion of the transition metal. Furthermore, transition metals (Mn, Fe, Co, Ni, and, Cu) are present at the grain boundaries at substantial solubility levels of ≈1022 cm−3, i.e., 1–2 orders of magnitude greater than in the bulk lattice. The observed dynamic behaviors of transition metals present a new perspective on the performance and durability of ceria‐containing applications.
“…CeO 2− δ , Sm 0.2 Ce 0.8 O 1.9− δ , ZrO 2− δ , and Y 0.08 Zr 0.92 O 1.96− δ poly-crystalline thin films were prepared by means of pulsed laser deposition (PLD) from oxide targets of the respective materials on single crystalline Al 2 O 3 (0001) substrates 10 × 10 × 0.65 mm 3 in size (Dasom RMS, Korea). CeO 2− δ and Sm 0.2 Ce 0.8 O 1.9− δ targets were prepared by a combined EDTA–citrate complexing method 59 using Ce(NO 3 ) 3 ·6H 2 O (JUNSEI Japan, 99.99% purity) and Sm(NO 3 ) 3 ·6H 2 O (Alfa Aesar, 99.9% purity) precursors, and ZrO 2− δ , and Y 0.08 Zr 0.92 O 1.96− δ targets were synthesized by a conventional solid state method using ZrO 2 (Sigma Aldrich, 99.99% purity) and Y 2 O 3 (Sigma Aldrich, 99.99% purity) powders. A coherent COMPex Pro 205 KrF excimer laser, emitting at a wavelength of 248 nm, was used for ablation with the deposition parameters of a pulsed laser energy of 270 mJ and a laser repetition rate of 20 Hz.…”
Supported metal nanoparticles hold great promise for many fields, including catalysis and renewable energy. Here we report a novel methodology for the in situ growth of architecturally tailored, regenerative metal nanocatalysts that is applicable to a wide range of materials. The main idea underlying this strategy is to selectively diffuse catalytically active metals along the grain boundaries of host oxides and then to reduce the diffused metallic species to form nanoclusters. As a case study, we choose ceria and zirconia, the most recognized oxide supports, and spontaneously form various metal particles on their surface with controlled size and distribution. Metal atoms move back and forth between the interior (as cations) and the exterior (as clusters) of the host oxide lattice as the reductive and oxidative atmospheres repeat, even at temperatures below 700 °C. Furthermore, they exhibit excellent sintering/coking resistance and reactivity toward chemical/electrochemical reactions, demonstrating potential to be used in various applications.
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