Effect of transition metal doping on the sintering and electrochemical properties of GDC buffer layer in SOFCs

A dense Ce_0.9Gd_0.1O_2−d (GDC) interlayer is an essential component of the SOFCs to inhibit interfacial elemental diffusion between zirconia-based electrolytes (eg YSZ) and cathodes. However, the characteristic high sintering temperature of GDC (>1400°C) makes it challenging to fabricate an effective highly dense interlayer owing to the formation of more resistive (Zr,Ce)O₂ interfacial solid solutions with YSZ at those temperatures. To fabricate a useful GDC interlayer, we studied the influence of transition metal (TM) (Co, Cu, Fe, Mn, & Zn) doping on the sintering and electrochemical properties of GDC. Dilatometry data showed dramatic drops in the necking and final sintering temperatures for the TM-doped GDCs, improving the densification of the GDC in the order of Fe > Co > Mn > Cu > Zn. However, the electrochemical impedance data showed that among various transition metal dopants, Mn doping resulted in the best electrochemical properties. Anode supported SOFCs with Mn-doped, nano, and commercial-micron GDC interlayers were compared with regard to their performance and stability levels. Although all of the SOFCs showed stable performance, the SOFC with the Mn-doped GDC interlayer showed the highest power density of 1.14 W cm⁻² at 750°C. Hence, Mn-doped GDC is suggested for application as an effective diffusion barrier layer in SOFCs.     

Solvent-deficient method lowers grain-boundary resistivity of doped ceria

Nanoparticles of gadolinium-doped cerium oxide (GDC) were synthesized using solvent-deficient method and their sinterability and electrical properties were investigated using the powder and cold sintering process. The GDC powder was uniaxially pressed into cylindrically-shaped pellets with a mixture of nitric acid and hydrogen peroxide at 200°C to encourage particle arrangement during forming process. These bulk samples were annealed using two different temperature profiles: at 800°C for 5 hours and at 1300°C for 1 minute—800°C for 5 hours. The samples produced using HNO₃/H₂O₂ mixture showed higher relative density than ones without it. Ionic conductivity of the sample sintered through the two-step profile was obtained from electrochemical impedance spectroscopy. Although the grain conductivity for the samples (8.0 × 10⁻³ S cm⁻¹ at 500°C, and 3.3 × 10⁻² S cm⁻¹ at 700°C) is on par with a conventionally sintered sample, the measured total conductivity (3.9 × 10⁻³ S cm⁻¹ at 500°C, and 2.5 × 10⁻² S cm⁻¹ at 700°C) is about 10 times higher than the conventionally sintered one and is comparable to the values seen in the previous studies for GDC which employed higher sintering temperature, pointing to the effectively lower grain-boundary impedance. This result could be attributed to no significant phase segregation along grain boundaries due to the low-temperature processing.     

Development of solid oxide cells by co-sintering of GDC diffusion barriers with LSCF air electrode

The effects of a Cu-based additive and nano-Gd-doped ceria (GDC) sol on the sintering temperature for the construction of solid oxide cells (SOCs) were investigated. A GDC buffer layer with 0.25–2 mol% CuO as a sintering aid was prepared by reacting GDC powder and a CuN₂O₆ solution, followed by heating at 600 °C. The sintering of the CuO-added GDC powder was optimized by investigating linear shrinkage, microstructure, grain size, ionic conductivity, and activation energy at temperatures ranging from 1000 to 1400 °C. The sintering temperature of the CuO–GDC buffer layer was decreased from 1400 °C to 1100 °C by adding the CuO sintering aid at levels exceeding 0.25 mol%. The ionic conductivity of the CuO–GDC electrolyte was maximized at 0.5 mol% CuO. However, the addition of CuO did not significantly affect the activation energy of the GDC buffer layer. Buffer layers with CuO-added GDC or nano-GDC sol-infiltrated GDC were fabricated and tested in co-sintering (1050 °C, air) with La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF). In addition, SOC tests were performed using button cells (active area: 1 cm²) and five-cell (active area: 30 cm²/cell) stacks. The button cell exhibited the maximum power density of 0.89 W cm⁻² in solid oxide fuel cell (SOFC) mode. The stack demonstrated more than 1000 h of operation stability in solid oxide electrolysis cell (SOEC) mode (decay rate: 0.004%/kh).     

Effect of Sm and Gd dopants on structural characteristics and ionic conductivity of ceria

Sm- and Gd-doped ceria electrolytes Ce_0.9Gd_0.1O_1.95 (GDC) and Ce_0.9Sm_0.1O_1.95 (SDC) were prepared by using the Pechini method. The microstructural and physical properties of the samples were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetry/differential thermal analysis (TG/DTA) and Fourier Transform Infrared Spectroscopy (FTIR). The TG/DTA and XRD results indicated that a single-phase fluorite structure formed at a relatively low calcination temperature, 400 °C. The XRD patterns of the samples revealed that the crystallization of the SDC powders was superior than that of the GDC powders at 400 °C. The sintering behavior and ionic conductivity of the GDC and SDC pellets were also investigated. The sintering results showed that the SDC samples were found to have higher sinterability than the GDC samples at a relatively low sintering temperature, 1300 °C, a significantly lower temperature than 1650 °C, which is required for ceria solid electrolytes prepared by solid state techniques. The impedance spectroscopy results revealed that SDC has a higher ionic conductivity compared to GDC.     

Effect of GDC addition method on the properties of LSM–YSZ composite cathode support for solid oxide fuel cells

Equal amounts of Gd_0.1Ce_0.9O_2−δ (GDC) were added to La_0.65Sr_0.3MnO_3−δ/(Y₂O₃)_0.08(ZrO₂)_0.92 (LSM/YSZ) powder either by physical mixing or by sol–gel process, to produce a porous cathode support for solid oxide fuel cells (SOFCs). The effect of the GDC mixing method was analyzed in view of sinterability, thermal expansion coefficient, microstructure, porosity, and electrical conductivity of the LSM/YSZ composite. GDC infiltrated LSM/YSZ (G-LY) composite showed a highly porous microstructure when compared with mechanically mixed LSM/YSZ (LY) and LSM/YSZ/GDC (LYG) composites. The cathode support composites were used to fabricate the button SOFCs by slurry coating of YSZ electrolyte and a nickel/YSZ anode functional layer, followed by co-firing at 1250 °C. The G-LY composite cathode-supported SOFC showed maximum power densities of 215, 316, and 396 mW cm⁻² at 750, 800, and 850 °C, respectively, using dry hydrogen as fuel. Results showed that the GDC deposition by sol–gel process on LSM/YSZ powder before sintering is a promising technique for producing porous cathode support for the SOFCs.     

Liquid‐phase sintering of highly Na+ ion conducting Na3Zr2Si2PO12 ceramics using Na3BO3 additive

Na₃Zr₂Si₂PO₁₂ (NASICON) is a promising material as a solid electrolyte for all‐solid‐state sodium batteries. Nevertheless, one challenge for the application of NASICON in batteries is their high sintering temperature above 1200°C, which can lead to volatilization of light elements and undesirable side reactions with electrode materials at such high temperatures. In this study, liquid‐phase sintering of NASICON with a Na₃BO₃ (NBO) additive was performed for the first time to lower the NASICON sintering temperature. A dense NASICON‐based ceramic was successfully obtained by sintering at 900°C with 4.8 wt% NBO. This liquid‐phase sintered NASICON ceramic exhibited high total conductivity of ~1 × 10^?3 S cm^?1 at room temperature and low conduction activation energy of 28 kJ mol^?1. Since the room‐temperature conductivity is identical to that of conventional high‐temperature‐sintered NASICON, NBO was demonstrated as a good liquid‐phase sintering additive for NASICON solid electrolyte. In the NASICON with 4.8 wt% NBO ceramic, most of the NASICON grains directly bonded with each other and some submicron sodium borates segregated in particulate form without full penetration to NASICON grain boundaries. This characteristic composite microstructure contributed to the high conductivity of the liquid‐phase sintered NASICON.     

Efficient strategy to boost the electrochemical performance of yttrium stabilized zirconia electrolyte solid oxide fuel cell for low-temperature applications

Yttrium stabilized zirconia (YSZ) used as the state-of-the-art electrolyte for solid oxide fuel cells (SOFCs) requires high temperature (over 800 °C) to realize sufficient oxygen ion conductivity. Thus, the high operational temperature is the main restriction for the commercial process of YSZ-based SOFCs. To obtain decent ionic conductivity at intermediate-low temperatures, Sr-free cathode LaNiO₃ is introduced into YSZ to construct a novel LaNiO₃-YSZ composite electrolyte, which is sandwiched by two Ni_0.8Co_0.15Al_0.05LiO_2-δ (NCAL) electrodes to assemble systematical fuel cells. This device presents an excellent peak output of 1045 mW cm^-2 at 600 °C and even 399 mW cm^-2 at 450 °C. A series of characterizations indicates that the oxygen ion conductivity of the LaNiO₃-YSZ composite is significantly promoted in comparison with that of pure YSZ, and the LaNiO₃ component has certain proton conductivity after hydrogenation. Both of the two factors contributes to the superior performance of such devices at intermediate-low temperatures. Furthermore, the sharp decrease in electronic conductivity for LaNiO₃ in hydrogen atmosphere combined with Schottky junction at the anode-electrolyte interface eliminates the short-circuiting problem. Our work demonstrates that incorporating Sr-free cathode LaNiO₃ into the YSZ electrolyte is an efficient strategy to boost the performance and reduce the operational temperature of YSZ-based SOFCs.     

Low-temperature constrained sintering of YSZ electrolyte with Bi2O3 sintering sacrificial layer for anode-supported solid oxide fuel cells

Solid oxide fuel cells (SOFCs) have strong potential for next-generation energy conversion systems. However, their high processing temperature due to multi-layer ceramic components has been a major challenge for commercialization. In particular, the constrained sintering effect due to the rigid substrate in the fabrication process is a main reason to increase the sintering temperature of ceramic electrolyte. Herein, we develop a bi-layer sintering method composed of a Bi₂O₃ sintering sacrificial layer and YSZ main electrolyte layer to effectively lower the sintering temperature of the YSZ electrolyte even under the constrained sintering conditions. The Bi₂O₃ sintering functional layer applied on the YSZ electrolyte is designed to facilitate the densification of YSZ electrolyte at the significantly lowered sintering temperature and is removed after the sintering process to prevent the detrimental effects of residual sintering aids. Subsequent sublimation of Bi₂O₃ was confirmed after the sintering process and a dense YSZ monolayer was formed as a result of the sintering functional layer-assisted sintering process. The sintering behavior of the Bi₂O₃/YSZ bi-layer system was systematically analyzed, and material properties including the microstructure, crystallinity, and ionic conductivity were analyzed. The developed bi-layer sintered YSZ electrolyte was employed to fabricate anode-supported SOFCs, and a cell performance comparable to a conventional high temperature sintered (1400 °C) YSZ electrolyte was successfully demonstrated with significantly reduced sintering temperature (<1200 °C).     

Electrical conductivity characteristics of Sr substituted layered perovskite cathode (SmBa0.5Sr0.5Co2O5+d) for intermediate temperature-operating solid oxide fuel cell

The high electrical conductivity of the cathode is one of the important factors for reducing the polarization resistance. For this reason, we here report the electrical conductivity characteristics of SmBa_0.5Sr_0.5Co₂O_5+δ (SBSCO) as a function of sintering temperature and current ranges. Calcined SBSCO samples were sintered at 1000, 1050, 1100, and 1150 °C. The current ranges applied in the process of measuring electrical conductivity were subdivided as 1.0A [0.05step], 0.5A [0.025step], and 0.1A [0.005step]. It was found that the sintering temperature affected the electrical conductivity in the following way: when the sintering temperature increases, an increase in the observed electrical conductivity is the result. However, as the current range decreases, it was found that the electrical conductivity would increase. The maximum and minimum conductivities of SBSCO sintered at 1150 °C were 2263S?cm^?1 at 50 °C and 382 S?cm^?1 at 900 °C with metallic behavior in air condition. When a current of 0.1A was applied to SBSCO sintered at 1150 °C, the electrical conductivity at the 800 °C was 1377.15 S/cm. It can be determined that the increase in the internal charge carrier flux of the SBSCO is associated with the decrease in the overall electrical conductivity of the Co-based metallic electrical conductivity. These results show that the high sintering temperature and low current range enable higher electrical conductivity at high operating temperature.     

A highly conductive Ce0.8Nd0.2O1.9 electrolyte with double sintering aids for intermediate-temperature solid oxide fuel cells

In this paper, the influence of Bi/Zn mass ratio on the phase composition, microstructure, sintering properties, and electrical properties of Bi/Zn co-added Nd_0.2Ce_0.8O_1.9 (NDC) used for intermediate-temperature solid oxide fuel cells (SOFCs) was investigated. At 700 °C, the total conductivity of the NDC-based electrolyte (3Bi/1Zn-NDC) with the mass ratio 3:1 for Bi₂O₃ and ZnO was as high as 5.89 × 10^?2 S cm^?1, 4.60 and 4.51 times higher than the single addition of 4 wt% Bi₂O₃ and 4 wt% ZnO, respectively. In addition, the 3Bi/1Zn-NDC electrolyte exhibited a good physical and chemical compatibility with the electrode materials. The open circuit voltage (OCV) of the cell supported by the 3Bi/1Zn-NDC electrolyte was 0.67 V, and the output power density could reach 402.25 mW cm^?2 at 700 °C. It showed stable power output and OCV in the long-term stability test within 50 h. Overall, the combination of 3 wt% Bi₂O₃ and 1 wt% ZnO was a very effective dual sintering aid for NDC electrolyte.     

Effects of CoO and Bi2O3 single/dual sintering aids doping on structure and properties of Ce0.8Nd0.2O1.9

Nd_0.2Ce_0.8O_3-δ (NDC) is one of the most common solid electrolyte materials used in solid oxide fuel cells (SOFCs). However, the densification temperature of NDC electrolyte is above 1400 °C. In this work, Bi₂O₃ and CoO sintering aids were individually or synergistically added to Nd_0.2Ce_0.8O_3-δ (NDC) electrolytes through the sol-gel method to lower its sintering temperature. Effects of Bi₂O₃-CoO dual sintering aid on the sintering behavior, phase composition, microstructure, and electrochemical properties of NDC electrolyte were all investigated. The data revealed that Bi₂O₃-CoO dual-sintering aid doped-NDC (labeled as NDC-CB) possessed high density and superior conductivity at low temperatures, better than that of Bi₂O₃ or CoO single sintering aid. NDC electrolyte doped with Bi₂O₃-CoO dual-sintering aid achieved highest relative density of 95.3% at 1100 °C and total conductivity of 5.765 × 10^-2 S cm^-1 at 800 °C. Furthermore, NDC-CB displayed excellent physical and chemical compatibility with La_0.6Sr_0.4Co_0.8Fe_0.2O_3-δ (LSCF) cathode and NiO-NDC anode. Oxygen reduction reaction at LSCF/NDC-CB interface was improved by about 40% when compared to NDC. In sum, Bi₂O₃-CoO looks promising as dual-sintering additive for lowing sintering temperature and increasing electrical conductivity of NDC. Therefore, NDC-CB might be potential electrolyte for future intermediate-temperature solid oxide fuel cells (IT-SOFCs).     

Synthesis and sodium ionic conductivity for perovskite-structured Na0.25La0.25NbO3 ceramic

In this work, a perovskite-structured sodium ion conductor, Na_0.25La_0.25NbO₃ (NLNO) was developed from analogous Li_0.25La_0.25NbO₃ ceramic. NLNO ceramic was successfully synthesized by solid state reaction. The sodium ionic conduction in Na_0.25La_0.25NbO₃ ceramic was studied and the effect of sintering temperature on the microstructure, phase structure, density and sodium ionic conductivity for Na_0.25La_0.25NbO₃ was also discussed. Single phase of perovskite was successfully obtained from NLNO sintered at 1200 °C and 1250 °C, and the result shows high sintering temperature leads to a large grain size, large lattice parameters and high density. With an increase of sintering temperature from 1150 °C to 1250 °C, the conductivity of samples increases gradually. NLNO sintered at 1250 °C presents a high sodium ionic conductivity of 1.06 × 10^?5 S cm^?1 at 30 °C, which is much higher than that of electronic conductivity in NLNO sintered at 1250 °C.     

Improved microstructure and sintering temperature of bismuth nano-doped GDC powders synthesized by direct sol-gel combustion

To improve the microstructural and electrochemical properties of Gadolinium-doped ceria (GDC) electrolytes, materials co-doped ceria with bismuth oxide (1–5 mol%) have been successfully prepared in a one-step sol-gel combustion synthetic route. Sol-gel combustion facilitates molecular mixing of the precursors and substitution of the large Bi³⁺ cations into the fluorite structure, considerably reducing the sintering temperature. Adding Bi₂O₃ as a dopant increases the GDC densification to above 99.7% and reduces its traditional sintering temperature by 300 °C. Impedance analyses show that the addition of bismuth enhances the conductivity (3.1?10^?2?1.7?10^?1 S·cm^?1 in the temperature range 600–800 °C) and improves the performance of the solid electrolyte in intermediate-temperature solid oxide fuel cells.     

Flexural strength and flaw distributions of SrFe0.2Co0.4Mo0.4O3−δ ceramic-supports for SOFCs at operating conditions

Solid-oxide fuel cells (SOFCs) have the potential to increase electricity generation efficiency, but traditional SOFCs supported by nickel cermets suffer from reliability challenges due to weaker mechanical strength caused by cracking after redox cycling. To solve this problem, a new ceramic anode material, SrFe_0.2Co_0.4Mo_0.4O_3−δ (SFCM) combined with Ce_0.9Gd_0.1O₂ (GDC), was evaluated for conductivity and mechanical strength at SOFC operating conditions and after redox cycling. Fracture toughness of SFCM was determined to be (0.124 ± 0.023) MPa√m at room temperature in air, increasing to (0.286 ± 0.038) MPa√m at 600°C. A mixture of SFCM:GDC showed fracture toughness between the two materials, following SFCM's trend with temperature. The SFCM-GDC anode supported half-cell strength increases by 31% from room temperature to 600°C as intrinsic stresses remaining from sintering are relaxed and thermal expansion pushes existing cracks closed. Exposure to reducing gasses decreases strength by 29% compared to ambient, due to oxygen vacancy formation and microstructural flaw changes. It is found that SFCM-GDC based cells tolerate cycling well because of phase stability but weaken from 34.3 to 22.4 MPa due to uniform growth of critical microstructural flaws.     

Enhanced sintering behavior of LSGM electrolyte and its performance for solid oxide fuel cells deposited by vacuum cold spray

How to obtain dense La_0.8Sr_0.2Ga_0.8Mg_0.2O₃ (LSGM) electrolyte at low sintering temperature (<1300 °C) is a challenge to improve solid oxide fuel cell (SOFC) performance at intermediate operation temperature. In this study, a double-layer design method for vacuum cold spray (VCS) prepared-LSGM electrolyte assisted with two-step sintering at a low temperature was proposed. The sintering behavior of VCS deposited LSGM layers at 1200 °C was investigated. The LSGM layers became denser in most regions except the appearance of some cracks. Subsequently, the effect of a second LSGM layer on the sintered top layer was studied to block cracks. Results showed that the co-sintered layer with a thickness of approximately 5 μm presented a maximum open circuit voltage of ∼0.956 V at 650 °C and a maximum power density of 592 mW/cm² at 750 °C. Result indicates that the sintering assisted VCS is a promising method to prepare the LSGM electrolyte applied in intermediate temperature SOFCs.     

Synthesis of Ga-doped Li7La3Zr2O12 solid electrolyte with high Li+ ion conductivity

Garnet-type Li₇La₃Zr₂O₁₂ (LLZO) Li⁺ ion solid electrolyte is a promising candidate for next generation high-safety solid-state batteries. Ga-doped LLZO exhibits excellent Li⁺ ion conductivity, higher than 1 × 10^?3 S cm^?1. In this research, the doping amount of Ga, the calcination temperature of Ga-LLZO primary powders, the sintering conditions and the evolution of grains are explored to demonstrate the optimum parameters to obtain a highly conductive ceramics reproducibly via conventional solid-state reaction methods under ambient air sintering atmosphere. Cubic LLZO phase is obtained for Li_6.4Ga_0.2La₃Zr₂O₁₂ powder calcined at low temperature 850 °C. In addition, ceramic pellets sintered at 1100 °C for 320 min using this powder have relative densities higher than 94% and conductivities higher than 1.2 × 10^?3 S cm^?1 at 25 °C.     

Direct evidence of high oxygen ion conduction of perovskite-type ceramic membrane under hydrogen atmosphere in solid oxide fuel cell

The ionic conduction of perovskite-type oxides remains a fundamental and important issue in the research of solid oxide fuel cells (SOFCs). In this research, a thin perovskite-type ceramic membrane was fabricated in situ at anode side attached to the surface of Gd_0.2Ce_0·8O_1.9 (GDC20) electrolyte membrane. The single cell working between H₂ and static air showed good stability (over 50 h), high open circuit voltages (above 1.0 V) as well as high peak power densities (749-264 mW cm^?2) from 600 to 500 °C. Detailed analyses of current research demonstrated that the thin perovskite film mainly possessed the oxygen ion conductivity under reducing atmosphere, while the proton conductivity was severely suppressed, showing the high flexibility in ionic conductivity of perovskite oxide. This work also implies that the oxygen ion and proton conduction may be in high correlation with each other, which provides important information to unveil the nature of the ionic conduction of perovskite-type oxides.     

Optimisation and Evaluation of La0.6Sr0.4CoO3 – δ Cathode for Intermediate Temperature Solid Oxide Fuel Cells

In this work, La_0.6Sr_0.4CoO_{3 – δ}/Ce_{1 – x}Gd_xO_{2 – δ} (LSC/GDC) composite cathodes are investigated for SOFC application at intermediate temperatures, especially below 700 °C. The symmetrical cells are prepared by spraying LSC/GDC composite cathodes on a GDC tape, and the lowest polarisation resistance (R_p) of 0.11 Ω cm² at 700 °C is obtained for the cathode containing 30 wt.‐% GDC. For the application on YSZ electrolyte, symmetrical LSC cathodes are fabricated on a YSZ tape coated on a GDC interlayer. The impact of the sintering temperature on the microstructure and electrochemical properties is investigated. The optimum temperature is determined to be 950 °C; the corresponding R_p of 0.24 Ω cm² at 600 °C and 0.06 Ω cm² at 700 °C are achieved, respectively. An YSZ‐based anode‐supported solid oxide fuel cell is fabricated by employing LSC/GDC composite cathode sintered at 950 °C. The cell with an active electrode area of 4 × 4 cm² exhibits the maximum power density of 0.42 W cm^–2 at 650 °C and 0.54 W cm^–2 at 700 °C. More than 300 h operating at 650 °C is carried out for an estimate of performance and degradation of a single cell. Despite a decline at the beginning, the stable performance during the later term suggests a potential application.     

Synthesis of Yb and Sc stabilized zirconia electrolyte (Yb0.12Sc0.08Zr0.8O2–δ) for intermediate temperature SOFCs: Microstructural and electrical properties

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_0.12Sc_0.08Zr_0.8O_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.     

Boosting intermediate temperature performance of solid oxide fuel cells via a tri-layer ceria–zirconia–ceria electrolyte

Using cost-effective fabrication methods to manufacture a high-performance solid oxide fuel cell (SOFC) is helpful to enhance the commercial viability. Here, we report an anode-supported SOFC with a three-layer Gd_0.1Ce_0.9O_1.95 (gadolinia-doped-ceria [GDC])/Y_0.148Zr_0.852O_1.926 (8YSZ)/GDC electrolyte system. The first dense GDC electrolyte is fabricated by co-sintering a thin, screen-printed GDC layer with the anode support (NiO–8YSZ substrate and NiO–GDC anode) at 1400°C for 5 h. Subsequently, two electrolyte layers are deposited via physical vapor deposition. The total electrolyte thickness is less than 5 μm in an area of 5 × 5 cm², enabling an area-specific ohmic resistance as low as 0.125 Ω cm⁻² at 500°C (under open circuit voltage), and contributing to a power density as high as 1.2 W cm⁻² at 650°C (at an operating cell voltage of 0.7 V, using humidified [10 vol.% H₂O] H₂ as fuel and air as oxidant). This work provides an effective strategy and shows the great potential of using GDC as an electrolyte for high-performance SOFC at intermediate temperature.