Enhanced ionic conductivity in calcium doped ceria – Carbonate electrolyte: A composite effect

Recently, ceria-based nanocomposites, as a proton and oxygen ion conductor, has been developed as promising electrolyte candidates for low-temperature solid oxide fuel cells (LTSOFCs). Up to now, samarium doped ceria (SDC) was studied as a main oxide for nanocomposite electrolyte; while calcium doped ceria (CDC) is considered as a good alternative from both material performance and economical aspects. Yet the conduction behavior of CDC-based composite has not been reported. In the present study, calcium doped ceria was prepared by oxalate co-precipitation method, and used for the fabrication of CDC/Na₂CO₃ composite. The thermal decomposition process, structure and morphology of the samples were characterized by TGA, XRD, SEM, etc. The oxygen ion conductivity of single phase CDC sample was measured by electrochemical impedance spectroscopy (EIS), while the proton and oxygen ion conductivity of CDC/Na₂CO₃ nanocomposite sample were determined by four-probe d.c. measurements. The CDC/Na₂CO₃ samples show significantly enhanced overall ionic conductivity compared to that of single phase CDC samples, demonstrating pronounced composite effect. This confirms that the use of nanocomposite as electrolyte can effectively lower the operation temperature of SOFC due to improved ionic conductivity.     

SDC/Na2CO3 nanocomposite: New freeze drying based synthesis and application as electrolyte in low-temperature solid oxide fuel cells

A key issue to develop low-temperature solid oxide fuel cells (LTSOFCs) is to develop new electrolyte materials with enhanced ionic conductivity. Recently, SDC/Na₂CO₃ nanocomposite, as a proton and oxide co-ion conductor, has been developed as promising electrolyte candidates for LTSOFCs, where Na₂CO₃ as the secondary phase performs several crucial functions. However, it’s difficult to control the homogeneity of Na₂CO₃ phase in the composite by the current methods for composite fabrication. In this study, we report a new freeze drying technique to fabricate SDC/Na₂CO₃ nanocomposites with different content of Na₂CO₃. Structural and morphological study confirmed that the homogeneity of both SDC and Na₂CO₃ phases in the nanocomposite is well controlled by the freeze drying technique. The effect of Na₂CO₃ content on proton and oxygen ion conductivities of SDC-carbonate samples were investigated by the four-probe d.c. measurement. Proton conductivity transformation around 350 °C has been observed for all the SDC/Na₂CO₃ nanocomposites due to the glass transition of amorphous Na₂CO₃ phase, and the proton conductivity is dependent on Na₂CO₃ content. While oxygen ion conductivity deceases with the increasing of Na₂CO₃ volume fraction in the nanocomposite. Finally, SOFCs were fabricated using SDC/Na₂CO₃ nanocomposite samples and tested for electrochemical performances. The excellent performance of SOFCs using SDC/Na₂CO₃ nanocomposite electrolyte verifies that nanocomposite approach is an effective way to fabricate electrolyte with enhanced ionic conductivity for LTSOFCs.     

Preparation and characterization of Sm0.2Ce0.8O1.9/Na2CO3 nanocomposite electrolyte for low-temperature solid oxide fuel cells

Sm_0.2Ce_0.8O_1.9 (SDC)/Na₂CO₃ nanocomposite synthesized by the co-precipitation process has been investigated for the potential electrolyte application in low-temperature solid oxide fuel cells (SOFCs). The conduction mechanism of the SDC/Na₂CO₃ nanocomposite has been studied. The performance of 20 mW cm⁻² at 490 °C for fuel cell using Na₂CO₃ as electrolyte has been obtained and the proton conduction mechanism has been proposed. This communication demonstrates the feasibility of direct utilization of methanol in low-temperature SOFCs with the SDC/Na₂CO₃ nanocomposite electrolyte. A fairly high peak power density of 512 mW cm⁻² at 550 °C for fuel cell fueled by methanol has been achieved. Thermodynamical equilibrium composition for the mixture of steam/methanol has been calculated, and no presence of C is predicted over the entire temperature range. The long-term stability test of open circuit voltage (OCV) indicates the SDC/Na₂CO₃ nanocomposite electrolyte can keep stable and no visual carbon deposition has been observed over the anode surface.     

Thermal stability study of SDC/Na2CO3 nanocomposite electrolyte for low-temperature SOFCs

The novel core–shell nanostructured SDC/Na₂CO₃ composite has been demonstrated as a promising electrolyte material for low-temperature SOFCs. However, as a nanostructured material, stability might be doubted under elevated temperature due to their high surface energy. So in order to study the thermal stability of SDC/Na₂CO₃ nanocomposite, XRD, BET, SEM and TGA characterizations were carried on after annealing samples at various temperatures. Crystallite sizes, BET surface areas, and SEM results indicated that the SDC/Na₂CO₃ nanocomposite possesses better thermal stability on nanostructure than pure SDC till 700 °C. TGA analysis verified that Na₂CO₃ phase exists steadily in the SDC/Na₂CO₃ composite. The performance and durability of SOFCs based on SDC/Na₂CO₃ electrolyte were also investigated. The cell delivered a maximum power density of 0.78 W cm⁻² at 550 °C and a steady output of about 0.62 W cm⁻² over 12 h operation. The high performances together with notable thermal stability make the SDC/Na₂CO₃ nanocomposite as a potential electrolyte material for long-term SOFCs that operate at 500–600 °C.     

Preparation and characterization of nanocrystalline Ce0.8Sm0.2O1.9 for low temperature solid oxide fuel cells based on composite electrolyte

Nanocrystalline Ce_0.8Sm_0.2O_1.9 (SDC) has been synthesized by a combined EDTA–citrate complexing sol–gel process for low temperature solid oxide fuel cells (SOFCs) based on composite electrolyte. A range of techniques including X-ray diffraction (XRD), and electron microscopy (SEM and TEM) have been employed to characterize the SDC and the composite electrolyte. The influence of pH values and citric acid-to-metal ions ratios (C/M) on lattice constant, crystallite size and conductivity has been investigated. Composite electrolyte consisting of SDC derived from different synthesis conditions and binary carbonates (Li₂CO₃–Na₂CO₃) has been prepared and conduction mechanism is discussed. Water was observed on both anode and cathode side during the fuel cell operation, indicating the composite electrolyte is co-ionic conductor possessing H⁺ and O²⁻ conduction. The variation of composite electrolyte conductivity and fuel cell power output with different synthesis conditions was in accordance with that of the SDC originated from different precursors, demonstrating O²⁻ conduction is predominant in the conduction process. A maximum power density of 817 mW cm⁻² at 600 °C and 605 mW cm⁻² at 500 °C was achieved for fuel cell based on composite electrolyte.     

Samarium doped ceria-(Li/Na)2CO3 composite electrolyte and its electrochemical properties in low temperature solid oxide fuel cell

A composite of samarium doped ceria (SDC) and a binary carbonate eutectic (52 mol% Li₂CO₃/48 mol% Na₂CO₃) is investigated with respect to its morphology, conductivity and fuel cell performances. The morphology study shows the composition could prevent SDC particles from agglomeration. The conductivity is measured under air, argon and hydrogen, respectively. A sharp increase in conductivity occurs under all the atmospheres, which relates to the superionic phase transition in the interface phases between SDC and carbonates. Single cells with the composite electrolyte are fabricated by a uniaxial die-press method using NiO/electrolyte as anode and lithiated NiO/electrolyte as cathode. The cell shows a maximum power density of 590 mW cm⁻² at 600 °C, using hydrogen as the fuel and air as the oxidant. Unlike that of cells based on pure oxygen ionic conductor or pure protonic conductor, the open circuit voltage of the SDC-carbonate based fuel cell decreases with an increase in water content of either anodic or cathodic inlet gas, indicating the electrolyte is a co-ionic (H⁺/O²⁻) conductor. The results also exhibit that oxygen ionic conductivity contributes to the major part of the whole conductivity under fuel cell circumstances.     

Effects of salt composition on the electrical properties of samaria-doped ceria/carbonate composite electrolytes for low-temperature SOFCs

Samaria-doped ceria (SDC)/carbonate composite electrolytes were developed for low-temperature solid oxide fuel cells (SOFCs). SDC powders were prepared by oxalate co-precipitation method and used as the matrix phase. Binary alkaline carbonates were selected as the second phase, including (Li–Na)₂CO₃, (Li–K)₂CO₃ and (Na–K)₂CO₃. AC conductivity measurements showed that the conductivities in air atmosphere depended on the salt composition. A sharp conductivity jump appeared at 475 °C and 450 °C for SDC/(Li–Na)₂CO₃ and SDC/(Li–K)₂CO₃, respectively. However, the conductivities of SDC/(Na–K)₂CO₃ increase linearly with temperature. Single cells based on above composite electrolytes were fabricated by dry-pressing and tested in hydrogen/air at 500–600 °C. A maximum power density of 600, 550 and 550 mW cm⁻² at 600 °C was achieved with SDC/(Li–Na)₂CO₃, SDC/(Li–K)₂CO₃ and SDC/(Na–K)₂CO₃ composite electrolyte, respectively, which we attribute to high ionic conductivities of these composite electrolytes in fuel cell atmosphere. We discuss the conduction mechanisms of SDC/carbonate composite electrolytes in different atmospheres according to defect chemistry theory.     

Performance of fuel cells with proton-conducting ceria-based composite electrolyte and nickel-based electrodes

A ceria-based composite electrolyte with the composition of Ce_0.8Sm_0.2O_1.9 (SDC)–30 wt.% (2Li₂CO₃:1Na₂CO₃) is developed for intermediate temperature fuel cells (ITFCs). Two kinds of SDC powders are used to prepare the composite electrolytes, which are synthesized by oxalate coprecipitation process and glycine–nitrate process, respectively, and denoted as SDC(OCP) and SDC(GNP). Based on each composite electrolyte, two single cells with the electrolyte thickness of 0.3 and 0.5 mm are fabricated by dry-pressing technique, using nickel oxide as anode and lithiated nickel oxide as cathode, respectively. With H₂ as fuel and air as oxidant, all the four cells exhibit excellent performances at 400–600 °C, which can be attributed to the highly ionic conducting electrolyte and the compatible electrodes. The cell performance is influenced by the SDC morphology and the electrolyte thickness. More interestingly, such composite electrolytes are found to be proton conductors at intermediate temperature range for the first time since almost all water is observed at the cathode side during fuel cell operation for all cases. The unusual transport property, excellent cell performance and potential low cost make this kind of composite material a good candidate electrolyte for future cost-effective ITFCs.     

Electrical properties of SDC–BCY composite electrolytes for intermediate temperature solid oxide fuel cell

The electrolyte material Ce_0.85Sm_0.15O_1.92 (SDC) powders are synthesized by glycine–nitrate processes and BaCe_0.83Y_0.17O_3−δ (BCY) powders are synthesized by sol–gel processes, respectively. Then SDC–BCY composite electrolytes are prepared by mixing SDC and BCY. The SDC and BCY powders are mixed in the weight ratio of 95:5, 90:10 and 85:15 and named as SB95, SB90 and SB85, respectively. The electrical properties of SDC and SDC–BCY composites are investigated. The experimental results show that SDC–BCY composites exhibit the excellent conductivity and could significantly enhance the fuel cell performances. The behavior that SDC–BCY composites display hybrid proton and oxygen ion conduction is substantiated. Among these electrolytes, the maximum power density reaches as high as 159 mW cm⁻² for the fuel cell based on SB90 composite electrolyte at 600 °C.     

Intermediate temperature fuel cell with a doped ceria-carbonate composite electrolyte

The performance of a composite electrolyte composed of a samarium doped ceria (SDC) and a binary eutectic carbonate melt phase has been examined. This material shows higher ionic conductivity than pure SDC in intermediate temperature region. SDC with different morphologies is obtained by co-precipitation, sol-gel and glycine-nitrate combustion preparation techniques. A tri-layer single cell is prepared with a cost-effective co-pressing and co-sintering technique. It is found that the surface properties of SDC and the electrolyte thickness have a great influence on the fuel cell performance. When the co-precipitated SDC is used as the electrolyte component and CO₂/O₂ gas mixture is adopted as the cathode oxidant gas, a fuel cell with an excellent performance is obtained, which has a peak power output of 1704 mW cm⁻² at a current density of 3000 mA cm⁻² at 650 °C. The influence of cathode atmosphere is examined with conductivity measurement and fuel cell performance test. The results support the concept of O²⁻/H⁺/CO₃²⁻ ternary conduction.     

Novel doped barium cerate–carbonate composite electrolyte material for low temperature solid oxide fuel cells

A composite of a perovskite oxide proton conductor (BaCe_0.7Zr_0.1Y_0.2O_3−δ, BCZ10Y20) and alkali carbonates (2Li₂CO₃:1Na₂CO₃, LNC) is investigated with respect to its morphology, conductivity and fuel cell performance. The morphology shows that the presence of carbonate phase improves the densification of oxide matrix. The conductivity is measured by AC impedance in air, nitrogen, wet nitrogen, hydrogen, and wet hydrogen, respectively. A sharp increase of the conductivity at certain temperature is seen, which relates to the superionic phase transition at the interface phases between oxide and carbonates. Single cell with the composite electrolyte is fabricated by dry-pressing technique, using nickel oxide as anode and lithiated nickel oxide as cathode, respectively. The cell shows a maximum power density of 957 mW cm⁻² at 600 °C with hydrogen as the fuel and oxygen as the oxidant. The remarkable proton conductivity and excellent cell performance make this kind of composite material a good candidate electrolyte for low temperature solid oxide fuel cells (SOFCs).     

Novel nanocomposite membranes based on PBI and doped-perovskite nanoparticles as a strategy for improving PEMFC performance at high temperatures

In this work, Sr²⁺ dopant effects of Ba_0.9Sr_0.1TiO₃ and La_0.9Sr_0.1CrO_3-δ doped-perovskite nanoparticles on increasing proton conductivity, fuel cell performance, and mechanical and thermal stability of polybenzimidazole-based nanocomposite membranes were studied. The Sr²⁺ dopant creates cation vacancies in Ba_0.9Sr_0.1TiO₃ doped-perovskite nanoparticles and oxygen vacancies in La_0.9Sr_0.1CrO_3-δ doped-perovskite nanoparticles. The oxygen vacancies, which decrease columbic repulsion between protons and positive ions, have a more important role than the cation vacancies. They provide high surface area and high interfacial interaction between La_0.9Sr_0.1CrO_3-δ doped-perovskite nanoparticles, phosphoric acid, and polybenzimidazole for proton transfer and increase the proton conductivity of the nanocomposite membranes. In addition, the results of relative humidity effects showed that the ordered arrangement of oxygen vacancies of the La_0.9Sr_0.1CrO_3-δ doped-perovskite nanoparticles creates a specific pathway in the nanocomposite membranes for increasing proton transfer in the presence of relative humidity. Furtheremore, at phosphoric acid doping level of 13 mol phosphoric acid per monomer unit, proton conductivity of the nanocomposite membranes containing 8 wt.% La_0.9Sr_0.1CrO_3-δ doped-perovskite nanoparticles was obtained as 126 mS cm^-1 at 180°C and 6% relative humidity. The nanocomposite membrane showed the best performance and the power density of 0.62 W cm^-2 at 180°C and 0.5 V.     

Ceria-carbonate composite for low temperature solid oxide fuel cell: Sintering aid and composite effect

In this study, the effect of carbonate content on microstructure, relative density, ionic conductivity and fuel cell performance of Ce_0.8Sm_0.2O_1.9-(Li/Na)₂CO₃ (SDC-carbonate, abbr. SCC) composites is systematically investigated. With the addition of carbonate, the nano-particles of ceria are well preserved after heat-treatment. The relative densities of SCC pellets increase as the carbonate content increases or sintering temperature rises. Especially, the relative density of SCC2 sintered at 900 °C is higher than that of pure SDC sintered at 1350 °C. Both the AC conductivity and DC oxygen ionic conductivity are visibly improved compared with the single phase SDC electrolyte. Among the composites, SDC-20 wt% (Li/Na)₂CO₃ (SCC20) presents high dispersion, relative small particle size, and the dense microstructure. The optimized microstructure brings the best ionic conductivity and fuel cell performance. It is hoped that the results can contribute the understanding of the role of carbonate in the composite materials and highlight their prospective application.     

Electrochemical performance of a new structured low temperature SOFC with BZY electrolyte

A symmetrical solid oxide fuel cell (SOFC) with a novel microstructure of BaZr_0.9Y_0.1O_3–δ (BZY) as the electrolyte is investigated in this study. The cell with the Ni_0.8Co_0.15Al_0.05LiO₂ (NCAL)-foam Ni/BZY/foam Ni-NCAL structure is prepared by a co-pressing method. The maximum obtained power density is 735.6 mW cm^?2 in H₂ at 550 °C, which is comparable to the results obtained using Ni cermet anode-supported SOFCs with an extremely thin electrolyte. The ionic conductivity of the BZY electrolyte prepared in this study is much higher than that of the conventional BZY electrolyte. The activation energy of ionic conduction is much lower than that of traditional oxygen ion or proton conduction. Electrochemical impedance spectra (EIS) results of the cell with the BZY electrolyte measured in different atmospheric conditions and the results of oxygen ion filtration experiments for the cell using the BZY/Ce_0.9Gd_0.1O₂ (GDC) bilayer electrolyte indicate that oxygen ion is one of the carriers in the BZY electrolyte prepared in this study. According to the results of X-ray photoelectron spectroscopy (XPS) and Fourier Transform infrared spectroscopy (FTIR), an interfacial O^2? conduction mechanism at the interface of BZY particles in the electrolyte is discussed.     

Electrochemical oxidation of graphite in an intermediate temperature direct carbon fuel cell based on two-phases electrolyte

As a promising intermediate temperature fuel cell, Direct Carbon Fuel Cell (DCFC) with composite electrolyte composed of Samarium-Doped Ceria (SDC) and a binary carbonate phase (67 mol% Li₂CO₃/33 mol% Na₂CO₃) has a much higher efficiency compared with conventional power suppliers. In the present work, SDC powder has been synthesized by an oxalate co-precipitation process and used as solid support matrix for the composite electrolyte. Single cell with composite electrolyte layer is fabricated by a dry-pressing technique using LiNiO₂/Li₂Na₂CO₃/SDC as cathode and 1:9 (weight ratio) graphite mixture with 67 mol% Li₂CO₃/33 mol% Na₂CO₃ molten carbonate as anode. The cell is tested at 600–750 °C using electrolytical graphite mixture as fuel and O₂/CO₂ mixture as oxidant. A relatively good performance with high power density of 58 mW cm⁻² at 700 °C is achieved for a DCFC using 0.8 mm thick composite electrolyte layer. The sensibility of the 1 cm² DCFC single cell performance to the anode gas nature is also investigated. At temperatures higher than 700 °C, both carbon (C) and carbon monoxide (CO) can be considered as reacting fuel for the DCFC system.     

Tuning an ionic-electronic mixed conductor NdBa0.5Sr0.5Co1.5Fe0.5O5+δ for electrolyte functions of advanced fuel cells

An ionic-conducting electrolyte mainly governs the solid oxide fuel cell performance. In this work, a mixed conductor NdBa_0.5Sr_0.5Co_1.5Fe_0.5O_5+δ was tuned as an electrolyte via compositing with a proton conductor BaZr_0.3Ce_0.6Y_0.1O_{3- δ} (BZCY), which realizes an ionic conductivity of 0.16 S cm^?1 at 550 °C along with fuel cell power density of 470 mW cm^?2. The 10 wt.% proton conducting BZCY can not only effectively block the electronic conductivity of NBSCF, but also greatly improve its ionic conductivity and the corresponding device's power output. The interfacial conduction could take a crucial role in the ion transporting process of BZCY-NBSCF composite. These interfaces or nanoscale grain boundaries formed amongst two phases keep excellent capability for designing and creating high performance electrochemical devices along with high-power density.     

Tuning semiconductor LaFe0.65Ti0.35O3-δ to fast ionic transport for advanced ceramics fuel cells

Heterostructure and their associated properties like band energy, band bending, and interface play a vital role in the conduction of charge carriers. Enhancement of ionic conductivity has been observed by the semiconductor SrTiO₃ and ionic conductor heterostructure formation, such insightful effect may be beneficial for electrolyte application in solid oxide fuel cells. Herein we report the formation of semiconductor and ionic materials heterostructure of LaFe_0.65Ti_0.35O_3-δ (LFT) and Sm and Ca co-doped cerium oxide Ce_0.8Sm_0.05Ca_0.15O_2-δ (SCDC) with three folds enhancement in the ionic conductivity. When LFT-SCDC heterostructure was applied in the fuel cell, LFT-SCDC work as a good electrolyte and achieve a maximum power output density of 0.98 W/cm². LFT-SCDC maintains the ionic and electronic conduction, the presence of electrons, their blockage and the fast promotion of ion transport play a key role in physical interpretation in realizing outstanding performance and understanding the mechanism of semiconductor electrolyte ceramics fuel cells. The constructed heterostructure between two different constituent phases of LFT and SCDC has established strong band bending at heterointerface, leading to the fast ionic transport in the interface. The combination of UV–visible spectroscopy and ultraviolet photoelectron spectroscopy (UPS) determine the band structure of both constituents, where the creation of oxygen vacancies are supported by X-ray photoelectron spectroscopy (XPS). It is revealed by the various investigation of electrical properties of LFT-SCDC heterostructure that it has both electronic and ionic behavior, where the built-in electric field formed by band energy alignment helps to enhance the transport of ions.     

A novel electronic current-blocked stable mixed ionic conductor for solid oxide fuel cells

A novel ionic conductor, BaCe_0.8Sm_0.2O_3−δ-Ce_0.8Sm_0.2O_2−δ (BCS-SDC, weight ratio 1:1), is reported as an electrolyte material for solid oxide fuel cells (SOFCs). Homogeneous BCS-SDC composite powders are synthesized via a one-step gel combustion method. The BCS and SDC crystalline grains play a role as matrix for each other in the composite electrolyte. The composite avoids the typical drawbacks of BCS and SDC, showing not only a better chemical stability than the single phase of BCS but much higher open circuit voltages (OCVs) than the single phase of SDC under the fuel cell conditions. Moreover, BCS-SDC exhibits mixed oxygen ionic and protonic conduction. A total conductivity of 0.0204 S cm⁻¹ at 700 °C is achieved in wet hydrogen (3% H₂O), the value of which is comparable with the state-of-the-art proton conductor BaZr_0.1Ce_0.7Y_0.2O_3−δ (BZCY). The peak power density achieves 505 mW cm⁻² at 700 °C with a 30-μm-thick BCS-SDC electrolyte using wet H₂ as the fuel. Resistances of the tested cell under open circuit conditions at different operating temperatures are also investigated by impedance spectroscopy.     

Conductivity of porous Sm2O3-doped CeO2 as a function of temperature and oxygen partial pressure

Porous samples of Sm₂O₃-doped CeO₂ (samaria-doped ceria, SDC) of composition Sm_0.15Ce_0.85O_2−δ were made by conventional ceramic processing and sintering in air at 1400 °C. Crystal structure and microstructure of the samples were characterized, respectively, by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Electrical conductivity was measured using a four probe DC method over a temperature range from 200 °C to 800 °C, and over a wide range of oxygen partial pressures corresponding to testing in oxygen and in nearly dry hydrogen. Conductivity rapidly stabilized at any given temperature consistent with the attainment of thermodynamic equilibrium corresponding to the imposed conditions. At and below 300 °C, the conduction was predominantly due to oxygen ion transport. At and above 400 °C, however, significant electronic conduction occurred in reducing atmospheres. The ionic transference number of SDC at 400 °C in hydrogen is only ∼0.4. This result shows that the electrolytic domain of SDC at and above 400 °C is rather narrow. These results also suggest that SDC (and possibly other rare earth oxide-doped CeO₂) is not a suitable electrolyte without a thin electron blocking layer such as yttria-stabilized zirconia (YSZ).     

Thermal, electrical and electrochemical characteristics of Ba1−xSrxCo0.8Fe0.2O3−δ cathode material for intermediate temperature solid oxide fuel cells

Ba_1−xSr_xCo_0.8Fe_0.2O_3−δ (x = 0.3-0.9) perovskite oxides have been studied as cathode material for intermediate temperature solid oxide fuel cells (IT-SOFCs). The structural characteristics, temperature dependent weight loss, thermal expansion, electrical conductivity, and electrochemical properties in combination with YSZ electrolyte together with an SDC buffer layer were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TG), dilatometry, DC four probe conductivity measurement and electrochemical impedance spectroscopy (EIS) techniques respectively. XRD study revealed the lattice parameter and unit cell volume decrease with increase in Sr⁺² content at the A-site. TEC and electrical conductivity were found to increase with increasing Sr⁺² content. Electrical conductivity was found to be dependent on the thermal history of the samples. Polarization resistance of the samples with SDC buffered YSZ electrolyte decreased with increasing Sr⁺² content which was ascribed to the higher conductivity with improved oxygen adsorption/desorption and oxygen ions diffusion processes. The intrinsic oxygen reduction reaction rate also increased with Sr⁺² content at the A-site. The exchange current for intrinsic oxygen reduction reaction at 700 °C was found to be 50.0 mA cm⁻² for Ba_0.3Sr_0.7Co_0.8Fe_0.2O_3−δ; a value which is about 50% higher than that for Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ, a widely studied cathode material. Therefore, the present composition may be a potential cathode material for IT-SOFC application.