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[Display omitted] • A comprehensive review of perovskite anode and cathode materials for SOFC has been provided. • The selection of initial composition, dopants addition with critical challenges have been assessed. • Doping strategies for energy storge applications were highlighted. • The problems and future directions of dopants addition on SOFCs were critically analyzed. Solid oxide fuel cells (SOFCs) have the potential to be used in energy conversion technology. Most of the studies aimed at modifications of anode concerning various issues such as component degradation, sulfur poisoning, and carbon deposition at high temperatures, hindering its applications at the industrial level. Different perovskite structure-related compounds are discussed in this article, which could be possible electrode materials in SOFCs. Literature also revealed the successful utilization of various cathode materials in a wide range of temperature in which cobalt-based materials exhibits higher conductivity than cobalt-free once. The selection of initial composition, dopants addition in different electrodes with critical challenges inherent to this material family have been assessed herein which play a vital role in enhanced electrochemical performance. The other aim of this review article is to provide some useful recommendations and prospective directions for designing future electrode materials of SOFCs. The review analysis is done based on different processing parameters and their effect on thermal expansion coefficient, electrical conductivity, mechanical and electrochemical properties, etc. In a nutshell, a detailed overview is critically analyzed for energy conversion and storage applications, which can open many gateways towards the advancement of SOFCs. [ABSTRACT FROM AUTHOR]

In this work, a critical evaluation of silver ion migration at the surface of Al 0.04 Sc 0.06 Zr 0.9 O 1.95 (AlScZrO) electrolyte is explored in intermediate temperature solid oxide fuel cells (IT-SOFCs). The behaviour of silver is systematically studied at the operating conditions of silver as a cathode, anode, or sealant in IT-SOFCs. The results to those obtained at the surface of other electrolytes (gadolinia doped ceria, samaria doped ceria and yttria-stabilized zirconia) are also analysed. In the case of cathodic polarization, a thick silver deposit is formed around the electrode on the surface of the electrolyte, which may lead to the short-circuiting of the electrodes. While for the anodic polarization, oxygen bubbles are formed between the electrode and electrolyte, leading the delamination of electrode. Silver can also migrate from unpolarized parts of the cell such as sealants. Therefore, Issues related to the application of silver in IT-SOFCs should be concerned by the scientific community. [Display omitted] • Dense AlScZrO electrolyte with high ionic conductivity developed using the Pechini method. • Assessment of silver ion migration in AlScZrO electrolyte at IT-SOFCs. • Ag migration issues leading to electrode delamination and short-circuit risks, hindering its viability in SOFCs. • Ag due to migration-induced electrode instability, discouraging its use as an electrode material or sealant. [ABSTRACT FROM AUTHOR]

High-conducting and long-term stable proton-conducting electrolytes are of utmost importance. This study investigates the synthesis and characterization of BaCe 0.7 Zr 0.1 Cu x Y 0.2-x O 3-δ (BCZCu x Y; x = 0, 0.005, 0.01, 0.02, 0.05, and 0.1) electrolytes tailored for proton-conducting solid oxide fuel cells (SOFCs). Through Cu2+ doping at the B-site of BaCe 0.7 Zr 0.1 Y 0.2 O 3-δ (BCZY), a successful reduction of the sintering temperature to 1200 °C was achieved. BCZCu 0.02 Y exhibited a high relative density of approx. 98.1% at this temperature, but beyond 2 mol% Cu doping, the appearance of a BaCuO 2 secondary phase adversely impacted conductivity. The electronic properties of BCZY and BCZCu x Y are elucidated via partial density of states (PDOS) analysis, revealing optimized crystal structures and band gap reductions (from approx. 1.9 eV–1.1 eV) upon Cu doping. Notably, BCZCu 0.02 Y demonstrated a commendable conductivity, with values of 3.5 × 10−2 S. cm−1 in air and 4.8 × 10−2 S. cm−1 in a moist atmosphere at 750 °C. Remarkably, excellent electrochemical stability was observed in a moist hydrogen atmosphere for up to 450 h at 600 °C. Single cells incorporating BCZCu 0.02 Y electrolytes exhibited peak power densities of 380 mW/cm2 at 750 °C. The incorporation of 2 mol% Cu2+ in the BCZY lattice holds promise for achieving low-temperature sintering and high-performance proton-conducting SOFCs. [ABSTRACT FROM AUTHOR]

Researchers' interest in proton-conducting reversible solid oxide cells (RSOCs) is growing due to their distinct benefits. In the present work, single-phase BaCe 0.9–x Mo x Y 0.1 O 3–δ (x = 0, 0.025, 0.05, 0.1, 0.2) electrolyte is prepared via sol-gel method and sintered at 1400 °C for 10 h. Optimal density, structure, composition, electrochemical performance, and thermal stability are confirmed via SEM, XRD, EDS, XPS, FTIR, EIS, and TGA/DSC. The conductivity of the grain interior and boundaries between 127 and 727 °C is reported for the first time in SOFC studies. The BaCe 0·875 Mo 0·025 Y 0·1 O 3–δ sample shows a grain interior conductivity of 1.3 × 10−3 S cm −1 at 707 °C with grain interior activation energy of 0.75 eV (127–727 °C), and a grain boundary activation energy of 0.85 eV (380–727 °C), 0.43 eV (167–357 °C) in air atmosphere, respectively. BaCe 0.875 Mo 0.025 Y 0.1 O 3–δ showed extreme stability for 300 h, and thus can be considered suitable for an efficient protonic conductor at intermediate temperatures. [Display omitted] • Mo-doped BaCe 0.9–x Mo x Y 0.1 O 3 (x = 0, 0.025, 0.05, 0.1, 0.2) were explored as IT-SOFCs. • BCY-0.025 Mo showed bulk activation energy of 0.63 eV (127–727 °C). • BCY-0.025 Mo showed grain boundary activation energy of 0.82 eV (167–357 °C). • TG/DSC results showed no observable mass loss until 700 °C for x = 0.025 and 0.05. • Long-term stability (300 h) was achieved using BaCe 0.875 Mo 0.025 Y 0.1 O 3. [ABSTRACT FROM AUTHOR]

BaCe 0.5 Zr 0.3 Y 0.2 O 3–δ (BCZY), regarded as one of the most promising proton–conducting electrolytes, often experiences difficulty because of its high sintering temperature. Here, a B–site doped BaCe 0.56 Zr 0.2 Ni 0.04 Y 0.2 O 3–δ (BCZNY) electrolytes were fabricated to address this drawback. The impact of Ni addition on sintering and electrical properties was examined. By adding Ni to the B–site of BCZY, a substantial decrease in the sintering temperature was achieved, i.e., from 1600 °C (for BCZY) to 1300 °C (for BCZNY). A conductivity of 0.05 S cm−1 at 700 °C was observed for BCZNY electrolyte in a moist nitrogen environment. In addition, SrFe 0.8 Mo 0.2 O 3–δ (SFM) is utilized as a symmetrical electrode material due to its high ionic and electronic conductivity. SFM electrode was synthesized via combustion process and exhibited suitable chemical and thermal compatibility with BCZY and BCZNY electrolytes up to 1100 °C. A single–phase cubic structure along with the surface morphology of electrolyte–supported symmetrical cells was confirmed by X–ray diffraction and scanning electron microscopy. Electrochemical impedance spectroscopy was conducted to identify the area–specific polarization resistance (ASR). The lowest ASR values of 0.037, 0.081, and 0.327 Ω cm2 at 800, 700, and 600 °C in humidified hydrogen were obtained in SFM-BCZNY composite electrode. The symmetrical cell achieved a peak power density of 254 m W cm−2 (cell configuration; SFM-BCZNY | BCZNY | SFM-BCZNY) at 800 °C. The fuel cell devices showed long–term stability of the fuel cell device for 100 h at 700 °C under a current of 120 mA cm−2. Considering the presented results, the as-prepared BCZNY is a promising protonic electrolyte for IT-SOFCs. [ABSTRACT FROM AUTHOR]

Ceramic electrolytes based on Yb and Sc stabilized zirconia enable efficient heat transfer and effective ionic conductivity. Here, the design and synthesis of Yb and Sc stabilized zirconia electrolyte is presented for intermediate temperature solid oxide fuel cells (SOFCs). Yb 0.12 Sc 0.08 Zr 0.8 O 2–δ was synthesized using the sol-gel method, and a thorough characterization of the electrolyte properties was conducted including structural and electrical properties. X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDS) confirmed the composition of the electrolyte. A single-phase cubic structure with a density of 6.7041 ± 0.0008 g cm−3 was obtained. The thermal expansion coefficient in the temperature range from 25 °C to 800 °C is equal to 1.17 × 10−6 K−1. The activation energy of 1.06 eV and 1.15 eV was obtained for the bulk and grain boundary conductivity, respectively. The ionic conductivity of approx. 2.10 S m−1 was achieved at 667 °C, thus it is suitable for efficient ionic conduction at intermediate temperatures. [ABSTRACT FROM AUTHOR]

LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCAL) has been extensively adopted as symmetric electrode for low temperature solid oxide fuel cells (SOFCs) based on oxide semiconductor electrolytes. However, the performance of NCAL electrode depend on material source, morphology and operating conditions. In this study, commercial microsphere NCAL is successfully modified with Na 2 CO 3 by a wet chemical method. The crystal structure, surface morphology, elemental analysis, surface chemistry and electrochemical properties of NCAL modified by Na 2 CO 3 (NCALN) are characterized by various techniques. When Na 2 CO 3 content in NCALN is 5 wt% and 10 wt%, the CeO 2 electrolyte SOFCs with NCALN symmetric electrode show significantly superior performance to that with NCAL symmetric electrode. The optimal heterostructure electrode NCALN5 exhibits a peak power density of 805 mW cm−2 and a polarization resistance of 0.237 Ω cm2 at 550 °C, which is 17 % higher and 21 % lower than those of NCAL electrode. Compared with NCAL electrode, NCALN5 electrode enhances the catalytic activities to both hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) but contributes more to ORR than HOR, especially at low temperatures. These results clearly demonstrate NCALN heterostructure composites are promising electrode materials for low temperature SOFCs. • LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCAL) was modified by Na 2 CO 3 as symmetric electrode. • The optimal NCAL heterostructure electrode has 5 wt% Na 2 CO 3. • NCALN5 showed excellent catalytic activity to ORR and HOR. • DRT was used to identify the role of NCALN5 electrode. [ABSTRACT FROM AUTHOR]

Solid Oxide Fuel Cells (SOFCs) have proven to be highly efficient and one of the cleanest electrochemical energy conversion devices. However, the commercialization of this technology is hampered by issues related to electrode performance degradation. This article provides a comprehensive review of the various degradation mechanisms that affect the performance and long-term stability of the SOFC anode caused by the interplay of physical, chemical, and electrochemical processes. In SOFCs, the most used anode material is nickel-yttria stabilized zirconia (Ni–YSZ) due to its advantages of high electronic conductivity and high catalytic activity for H 2 fuel. However, various factors affecting the long-term stability of the Ni–YSZ anode, such as redox cycling, carbon coking, sulfur poisoning, and the reduction of the triple phase boundary length due to Ni particle coarsening, are thoroughly investigated. In response, the article summarizes the state-of-the-art diagnostic tools and mitigation strategies aimed at improving the long-term stability of the Ni–YSZ anode. [Display omitted] • A review of the obstacle to SOFC commercial breakthrough, high degradation rates. • Ni–YSZ is a widely used anode material due to its high electronic conductivity and catalytic activity for H 2 fuel. • This article offers a comprehensive review of degradation mechanisms affecting the Ni–YSZ anode in SOFCs. • Enhancing SOFC performance and stability through doping, surface modifications, and interface engineering techniques. • The review presents advanced diagnostic tools and mitigation strategies for the improvement of Ni–YSZ anodes. [ABSTRACT FROM AUTHOR]

Low-temperature solid oxide fuel cells (LT-SOFCs) represent a cutting-edge solution in the domain of clean energy, poised to revolutionize electricity generation for both stationary and mobile applications. At the core of LT-SOFCs lies the proton-conducting solid oxide electrolyte, a subject of extensive exploration and advancement. This comprehensive review investigates the evolution of proton-conducting solid oxide electrolytes for LT-SOFCs, exploring the landscape from fundamental materials to diverse device architectures. The review meticulously examines three pivotal dimensions: 1) strategies for fine-tuning the properties and structures of ceramics and proton-conducting oxides, 2) advancements in techniques for protonic-conducting fuel cells (PCFCs), and 3) an exploration of the opportunities and challenges intrinsic to the progression of electrolyte-based PCFCs. By elucidating the advancements made in optimizing conductivity, chemical stability, sinterability, and electron-blocking characteristics of proton-conducting electrolytes, this review offers invaluable insights into the state-of-the-art for LT-SOFC technology. Furthermore, it casts a forward-looking perspective, envisioning the future trajectory of proton-conducting electrolyte research and its potential to reshape the landscape of LT-SOFC technology. By providing a comprehensive overview of past achievements and future prospects, this review serves as a valuable resource for researchers, engineers, and stakeholders, guiding them towards the realization of efficient and sustainable energy solutions. • Evolution of proton-conducting solid oxide electrolytes for LT-SOFCs. • Strategies for fine-tuning properties and structures of ceramics and oxides. • Advancements in techniques for protonic-conducting fuel cells (PCFCs). • Insights into conductivity, chemical stability, and electron-blocking characteristics. • Forward-looking perspective on the future trajectory of LT-SOFC technology. [ABSTRACT FROM AUTHOR]

• A comprehensive review of perovskite-based electrolyte materials for SOFC has been provided. • The selection of initial composition, dopants addition with critical challenges has been assessed. • Performance optimizing strategies for energy storage applications were highlighted. • The problems and future directions of dopants addition on SOFCs were critically analyzed. Solid oxide fuel cells (SOFCs) are found to have potential application in energy conversion technology due to their characteristics i.e., good modularization, better fuel efficiency, and lesser toxic products (CO 2 , SO x , and NO x). Mostly the electrolytic materials with ionic or protonic conductivity, undergo degradation at various operating conditions which must be prevented. Based on the above-mentioned problems, perovskites are considered as one of the wonderful classes of electrode and electrolyte materials with hydrocarbon fuels and retentivity of inherent stability at reducing/oxidizing atmosphere. In this review, recent developments in perovskite electrolyte materials of solid oxide fuel cells are summarized with prospects. Here, our main purpose is to deliver a brief tutorial corresponding to the structure, properties, and electrochemical behavior of perovskite-based electrolytes in test cells with various dopants together and inherited challenges regarding this material family. Several novel design strategies for the optimization of cell performance i.e., interface engineering, strain modulation, and defect engineering have been discussed in detail. In addition to this, a perspective has been proposed on the development routes or designs for perovskite oxide-based materials with high performance in energy conversion and storage applications as well as the way forward to cope with the challenges involved in the research route regarding the performance of each component. [Display omitted] [ABSTRACT FROM AUTHOR]

Fuel cell device efficiently can convert chemical-energy (CE) of hydrogen/hydrocarbon fuels to electrical-energy. From the various types of fuel cells, solid oxide fuel cell (SOFC) unifies the advantages of combined heat and power-output with multi-fuel-flexibility. Even so, the high operating temperatures (800-1,000 °C) leads to materials compatibility and high costs challenges. However, much progress has been made to develop low-temperature SOFCs. But poor oxygen reduction reaction (ORR) activity of traditional cathode materials at low temperatures is a key-bottleneck to reduce operating-temperature of SOFCs. Therefore, fundamental understanding of oxygen reduction reaction (ORR) is important for low-temperature solid oxide fuel cells (LT-SOFCs). Herein, we present a simple but very effective way to improve the ORR activity of an orthorhombic nanostructured CaFe 2 O 4 embedded on porous Ni-foam for low temperature for SOFCs cathode. The CaFe 2 O 4 embedded on Ni-foam exhibits a very low area-specific resistance (ASR) and excellent power output of 0.532 Wcm−2 at low operating temperature of 500 °C. The excellent ORR activity is mainly supported by the superficial release of oxygen ions with enhanced gas diffusion abilities of CaFe 2 O 4 by embedding on Ni-foam due to its highly porous structure. The electrical conductivity of CaFe 2 O 4 embedded on Ni-foam is also found to be increased dramatically. More importantly, formation of complex oxidation states (Fe2+/Ni3+ and Fe3+/Ni2+) between CaFe 2 O 4 and Ni-foam plays an important role on narrows the bandgap to improve the electrical conductivity and produce more oxygen vacancies to enhance the ionic transport. High electrical conductivity and electrocatalytic functionality of reported nanostructure insights new avenues for LT-SOFCs. In addition, various spectroscopies, such as UV-visible, Raman, and X-ray photoelectron spectroscopy are employed to catch the understandings of CaFe 2 O 4 embedded Ni-foam as new functional ORR electrocatalyst for advanced LT-SOFCs. [Display omitted] • Ni foam embedded CaFe 2 O 4 spinel ferrite is developed for LT-SOFCs cathode. • Ni-foam embedded CaFe 2 O 4 cathode shows highly porous structure. • The ORR activity of CaFe 2 O 4 is greatly improved by embedding it on Ni foam. • The excellent electrochemical performance of the of 0.532 W cm−2 at 500 °C was achieved. • It show low charge and mass transfer losses. [ABSTRACT FROM AUTHOR]

This review article explores recent advancements and potential advantages of low-temperature solid oxide fuel cells (LT-SOFCs), offering a comprehensive overview of critical developments in the field. It highlights the significance of utilizing oxygen ion conducting electrolytes such as La 0.8 Sr 0.2 Ga 0.8 Mg 0.2 O 3 –type (LSGM) perovskties and yttria-stabilized zirconia (YSZ) in LT-SOFCs, emphasizing their role in facilitating efficient oxygen transport at lower temperatures. Furthermore, the review discusses the importance of electrode tailoring at the nanoscale using techniques like sol-gel and pulsed laser deposition (PLD), which have been shown to enhance the oxygen reduction reaction (ORR) at the cathode, thereby improving overall cell performance. One of the key focal points of the review is the exploration of perovskite structures and their imperative characteristics in LT-SOFCs. Specifically, it elucidates how oxygen defects within perovskites contribute to the migration of oxygen ions, consequently augmenting electrical conductivity within the cell. This discussion underscores the significance of understanding the fundamental principles governing ion transport mechanisms in electrolyte materials, which is crucial for the development of next-generation LT-SOFCs with improved efficiency and performance. Moreover, the review highlights recent advancements in the fabrication of nanoscale electrolyte films, which have shown promising results in reducing series resistance and enhancing cell performance at lower temperatures. Techniques such as atomic layer deposition (ALD), and spark plasma sintering (SPS) are discussed in the context of fabricating these nanoscale membranes, underscoring their potential for revolutionizing LT-SOFC technology. Overall, this review consolidates recent research findings and technological advancements in the field of LT-SOFCs, shedding light on the novel approaches and strategies employed to overcome existing challenges and propel the development of more efficient and practical fuel cell systems. By synthesizing key insights and highlighting future research directions, this review serves as a valuable resource for researchers and engineers working towards the advancement of LT-SOFC technology. [Display omitted] • Nanoscale zirconia electrolyte membranes offer enhanced efficiency in LT-SOFCs. • Comprehensive overview of electrode design challenges and solutions. • Insights into hydrogen spillover mechanisms at Ni-YSZ interfaces. • Innovations in nickel-based anodes for improved LT-SOFC performance. • Exploration of advanced electrolyte technologies for enhanced fuel cell functionality. [ABSTRACT FROM AUTHOR]

This research is the continuation of our previous work, in which we introduced novel proton-conducting electrolytes BaCe 0.9–x Mo x Y 0.1 O 3–δ (BCM x Y; x = 0.025, 0.05). In this study, we explore the potential of the proton-conducting BCM 0.025 Y electrolyte by creating a composite with La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3–δ (LSCF) to form triple conducting electrodes for solid oxide fuel cells (SOFC). The formation of the LSCF-BCM 0.025 Y composite enhances both the three-phase reaction interface length and the concentration of oxygen vacancies, contributing to improved dissociation rates and enhanced oxygen adsorption. The desired characteristics, including density, structure, composition, electrochemical performance, and thermal stability, have been confirmed through a comprehensive set of analyses including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), electrochemical impedance spectroscopy (EIS), and thermogravimetric analysis (TGA) coupled with differential scanning calorimetry (DSC), respectively. The cell configuration of Ni-YSZ | BCZY | LSCF-BCM 0.025 Y exhibited a remarkable maximum power density (MPD) of 418.7 mW cm−2, which is approximately 29 % higher than that achieved with a typical LSCF cathode (325.6 mW cm−2) at an operating temperature of 600 °C. The outstanding performance and enduring stability of the LSCF-BCM 0.025 Y composite over a 500 h period demonstrate its potential as a promising cathode material for intermediate-temperature SOFCs. [Display omitted] • Significant enhancement in the three-phase reaction interface length with BCM x Y addition to LSCF cathodes. • LSCF-BCM 0.025 Y composite elevates SOFC oxygen electrode performance with enhanced dissociation rates and oxygen adsorption. • Exceptional maximum power density (MPD) of 418.7 mW cm−2, showcasing a 29 % increase over traditional LSCF cathodes. • Outstanding stability over 500 h showcases LSCF-BCM 0.025 Y as a promising SOFC cathode material. [ABSTRACT FROM AUTHOR]

[Display omitted] • New electrolytes Ba 0.5 Sr 0.5 Zr 0.9-x Gd x Y 0.1 O 3-δ (x = 0, 0.05, 0.1) were developed for SOFCs. • Power density of 805 mW cm−2 was achieved by the SOFC with BSZGd 0.1 Y at 520 °C. • Hybrid H+/O2– conductivity of 0.17 S cm−1 was detected in BSZGd 0.1 Y at 520 °C. • Crystal structure and electronic property of BSZGd 0.1 Y were studied by DFT calculation. • Successful demonstration of SOFC and SOEC by using BSZGd 0.1 Y electrolyte. A hybrid proton and oxide ion (H+/O2–) conducting electrolyte transports ions in multiple ways can operate at lower operating temperatures than a pure oxide ion conductor in solid oxide fuel cells (SOFCs). Here, a novel hybrid H+/O2– conductor is developed based on Ba 0.5 Sr 0.5 Zr 0.9 Y 0.1 O 3-δ (BSZY) by Gd3+ doping. The Ba 0.5 Sr 0.5 Zr 0.9-x Gd x Y 0.1 O 3-δ (x = 0, 0.05, 0.1) electrolytes are modeled to construct crystal structures by density functional theory (DFT) calculations and subsequently synthesized, followed by physicochemical characterizations. The corresponding BSZGd x Y electrolyte-based SOFCs are fabricated and investigated in terms of I-V characteristics, electrochemical impedance spectra, and durable operation. It is found Gd3+doping significantly enriches the oxygen vacancies and enhance the ionic conductivity of BSZGd x Y. The DFT calculations provide evidence of high oxygen vacancies formation with the optimal doping of Gd with x = 0.1. Among the three samples, the Ba 0.5 Sr 0.5 Zr 0.8 Gd 0.1 Y 0.1 O 3-δ (BSZGd 0.1 Y) electrolyte exhibits the highest fuel cell power density of 805 mW cm−2, hybrid H+/O2– conductivity of 0.17 S cm−1, and stable operation for 67 h at 520 °C. Further study finds that the BSZGd 0.1 Y electrolyte-based fuel cell can be operated under water electrolysis mode, revealing a high current density of 2.37 A cm−2 under 1.5 V at 520 °C. Moreover, the impact of Gd doping is studied in terms of electronic structure and energy bands investigated with the help of DFT calculations and the Schottky junction effect of the cell for electron blocking is investigated. This work demonstrates an efficient way to explore hybrid H+/O2– conduction in BSZY for high-performance SOFC and water electrolysis. [ABSTRACT FROM AUTHOR]

Zirconia based oxygen conductors are state of the art solid electrolytes used for solid oxide fuel cell applications. In this study, we investigated zirconia double-doped with aluminium and scandium oxide. The Al 0.04 Sc 0.06 Zr 0.9 O 1.95 electrolyte was prepared using Pechini method. In the 300–800 K temperature range, this material's structure is cubic with a fraction of monoclinic modification, while above 800 K it becomes completely cubic. The ceramic form of Al 0.04 Sc 0.06 Zr 0.9 O 1.95 electrolyte was investigated using broadband impedance spectroscopy, utilizing equivalent circuit analysis and distribution of relaxation times (DRT) technique. The high-frequency relaxation process's complexity observed in the spectra's DRT representation at temperatures up to 500 K was associated with the two zirconia phases. The Al 0.04 Sc 0.06 Zr 0.9 O 1.95 electrolyte was tested in a hydrogen-oxygen laboratory solid fuel cell in the temperature range 973–1123K. Understanding the fundamentals of the relaxation processes is necessary to increase the durability of the ceramic electrolyte in the fuel cell. [Display omitted] • Cubic (72 %) and monoclinic (28 %) phases of Al 0.04 Sc 0.06 ZrO 1.95 up to 800 K. • Two relaxation processes separated in ceramics grains. • Phase transition in AlSc-SZ leads to relaxation time activation energy change. [ABSTRACT FROM AUTHOR]

[Display omitted] • Diverse microstructures attainable via thermal spray techniques benefit SOFC technology. • Precise control of anode and cathode porosity aids gas diffusion and reactant transport. • Optimal conditions yield dense YSZ coatings suitable for SOFC electrolytes (20–50 μm). • PS-PVD method offers potential for ultra-thin electrolyte layers (<20 μm) via vapor–liquid co-deposition. • Plasma spray tech advances SOFCs, but microstructure control remains a key challenge. This article provides a comprehensive review of the microstructure development of plasma-sprayed ceramic coatings in relation to the deposition of functional layers within solid oxide fuel cells (SOFCs). The focus is primarily on thermal-sprayed porous coatings for both the anode and cathode, as well as plasma-sprayed dense ceramic coatings for the electrolyte, considering both post-treatment methods and processes without post-treatment. The review also encompasses the control of composition and crystalline structure in plasma-sprayed perovskite cathode materials. Furthermore, the article discusses the advantages, limitations, and prospects of utilizing thermal spray processes for the deposition of SOFC electrolytes. The design of highly efficient electrodes with enhanced triple-phase boundaries is introduced as a pivotal aspect. Additionally, the integrated fabrication of SOFCs through thermal spray techniques is presented to highlight the potential of these processes in manufacturing SOFCs with various configuration designs. [ABSTRACT FROM AUTHOR]