Electrically conductive SiC ceramics processed by pressureless sintering

Polycrystalline SiC ceramics with 10 vol% Y₂O₃-AlN additives were sintered without any applied pressure at temperatures of 1900-2050°C in nitrogen. The electrical resistivity of the resulting SiC ceramics decreased from 6.5 × 10¹ to 1.9 × 10⁻² Ω·cm as the sintering temperature increased from 1900 to 2050°C. The average grain size increased from 0.68 to 2.34 μm with increase in sintering temperature. A decrease in the electrical resistivity with increasing sintering temperature was attributed to the grain-growth-induced N-doping in the SiC grains, which is supported by the enhanced carrier density. The electrical conductivity of the SiC ceramic sintered at 2050°C was ~53 Ω⁻¹·cm⁻¹ at room temperature. This ceramic achieved the highest electrical conductivity among pressureless liquid-phase sintered SiC ceramics.     

A benzoate coprecipitation route for synthesizing nanocrystalline GDC powder with lowered sintering temperature

Electrolyte powders with low sintering temperature and high-ionic conductivity can considerably facilitate the fabrication and performance of solid oxide fuel cells (SOFCs). Gadolinia-doped ceria (GDC) is a promising electrolyte for developing intermediate- and low-temperature (IT and LT) SOFCs. However, the conventional sintering temperature for GDC is usually above 1200 °C unless additives are used. In this work, a nanocrystalline powder of GDC, (10 mol% Gd dopant, Gd_0.1Ce_0.9O_1.95) with low-sintering temperature has been synthesized using ammonium benzoate as a novel, environmentally friendly and cost-effective precursor/precipitant. The synthesized benzoate powders (termed washed- and non-washed samples) were calcined at a relatively low temperature of 500 °C for 6 h. Physicochemical characteristics were determined using thermal analysis (TG/DTA), Raman spectroscopy, FT-IR, SEM/EDX, XRD, nitrogen absorptiometry, and dilatometry. Dilatometry showed that the newly synthesized GDC samples (washed and non-washed routes) start to shrink at temperatures of 500 and 600 °C (respectively), reaching their maximum sintering rate at 650 and 750 °C. Sintering of pelletized electrolyte substrates at the sintering onset temperature for commercial GDC powder (950 °C) for 6 h, showed densification of washed- and non-washed samples, obtaining 97.48 and 98.43% respectively, relative to theoretical density. The electrochemical impedance spectroscopy (EIS) analysis for the electrolyte pellets sintered at 950 °C showed a total electrical conductivity of 3.83 × 10^?2 and 5.90 × 10^?2 S cm^?1 (under air atmosphere at 750 °C) for washed- and non-washed samples, respectively. This is the first report of a GDC synthesis, where a considerable improvement in sinterability and electrical conductivity of the product GDC is observed at 950 °C without additives addition.     

Microstructure and ionic conductivity of Li1.5Al0.5Ge1.5(PO4)3 solid electrolyte prepared by spark plasma sintering

In this paper, the microstructure and ionic conductivity of Li_1.5Al_0.5Ge_1.5(PO₄)₃ (LAGP) solid electrolytes prepared by spark plasma sintering (SPS) were investigated by XRD, SEM, TEM and EIS, respectively. The results showed that as the sintering temperature was increased, both the relative density and the ionic conductivity of the sintered LAGP samples first increased and then decreased, achieving a maximum value of 97% and 2.12 × 10⁻⁴ S cm⁻¹ simultaneously at 700 °C. At the same time, the crystallinity of the sintered samples was improved, while a few impurity phases, such as AlPO₄ and GeO₂, appeared in the samples. It was also found that carbon contamination and oxycarbide gas was be brought in during SPS. Carbon contamination could produce an extra grain boundary impedance to the samples and could be removed by annealing at 500 °C in an air atmosphere. Oxycarbide gas could affect the relative density of the sintered LAGP samples and could be mitigated by choosing a suitable SPS process. Moreover, the shear modulus of the sintered LAGP was measured to be 49.6 GPa, which exceeded the minimum value of 8.5 GPa that was necessary to suppress Li dendrite growth.     

Electrical characterization of La9.33Si2Ge4O26 oxyapatite for prospective intermediate-temperature solid oxide fuel cells

La_9.33Si₂Ge₄O₂₆ materials have been fabricated from La₂O₃, SiO₂ and GeO₂ powders by high speed mechanical alloying followed by conventional and microwave hybrid sintering at different temperatures and holding times. XRD data showed that the apatite phase is formed after 1 h of mechanical alloying at 850 rpm. This phase remained stable after conventional sintering in an electric furnace with density increasing as sintering temperatures and holding times were increased. However, the highest density was achieved for samples sintered in the microwave furnace (5.44 g cm⁻³), corresponding to a relative density of 98%. The electrical conductivity of the samples microwave sintered at 700 and 800 ºC are 4.72×10⁻³ and 1.93×10⁻² S.cm⁻¹, respectively, with a correspondent activation energy of 0.952 eV.     

Sintering temperature dependency on sodium-ion conductivity for Na2Zn2TeO6 solid electrolyte

We investigated the sintering temperature dependency on the properties of Na₂Zn₂TeO₆ (NZTO) solid electrolyte synthesized via a conventional solid-state reaction method. Sintering temperature of calcined NZTO powder, which was obtained by the calcination of precursor at 850℃, was changed in the range from 650 to 850℃. X-ray diffraction analysis showed that P2-type layered NZTO phase was formed in all sintered samples without forming any secondary phases. The relative densities of sintered NZTO samples were approximately 83%−85% for the samples sintered at 700℃ or higher. The all sintered samples showed sodium-ion conductivity above 10⁻⁴ S cm⁻¹ at room temperature and the highest conductivity of 4.0 × 10⁻⁴ S cm⁻¹ in the sample sintered at 750℃. The sintering temperature to obtain the highest room temperature conductivity is 100℃ lower than that used in previous works. Such low sintering temperature compared to other Na-based oxide solid electrolytes could be useful for co-sintering with electrode active materials for fabrication of all-solid-state sodium-ion battery.     

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.     

Final-stage densification kinetics of direct current–sintered ZrB2

Final-stage sintering was analyzed for nominally phase pure zirconium diboride synthesized by borothermal reduction of high-purity ZrO₂. Analysis was conducted on ZrB₂ ceramics with relative densities greater than 90% using the Nabarro–Herring stress–directed vacancy diffusion model. Temperatures of 1900°C or above and an applied uniaxial pressure of 50 MPa were required to fully densify ZrB₂ ceramics by direct current sintering. Ram travel data were collected and used to determine the relative density of the specimens during sintering. Specimens sintered between 1900 and 2100°C achieved relative densities greater than 97%, whereas specimens sintered below 1900°C failed to reach the final stage of sintering. The average grain size ranged from 1.0 to 14.7 μm. The activation energy was calculated from the slope of an Arrhenius plot that used the Kalish equation. The activation energy was 162 ± 34 kJ/mol, which is consistent with the activation energy for dislocation movement in ZrB₂. The diffusion coefficients for dislocation motion that controls densification were 5.1 × 10⁻⁶ cm²/s at 1900°C and 5.1 × 10⁻⁵ cm²/s at 2100°C, as calculated from activation energy and average grain sizes. This study provides evidence that the dominant mechanism for final-stage sintering of ZrB₂ ceramics is dislocation motion.     

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.     

Electrical characterization of mixed conducting SCY-YDC composite electrolyte

SrCe_0.9Y_0.1O_3-δ-Ce_0.9Y_0.1O_2-δ (SCY-YDC, 1:1 mole ratio), as a novel composite electrolyte, was successfully synthesized and characterized. X-ray diffraction patterns showed that SCY-YDC composite electrolyte is a mixture of SCY and YDC. Besides, no impurity phase emerged after sintering at 1550 °C for 10 h. AC impedance spectroscopy was used to determine the electrical properties of SCY-YDC at 500–800 °C in various atmospheres. Partial conductivities of oxygen vacancies, protons, and electrons (p-type) were calculated using the defect structure model. Results showed that SCY-YDC is a mixed (hole, proton, and oxygen-ion) conductor. Moreover, the contribution of holes is minor at 650–800 °C in high pressure (1 atm) or low pressure (10⁻⁴ atm) O₂ atmospheres. Dominant carrier switched from protons to oxygen ions as temperature increased at vapor pressure in air of 0.038 atm. Total conductivity for SCY-YDC is 6.19 × 10⁻³ S cm⁻¹ at 800 °C under pO₂ = 1 atm and pH₂O = 6 × 10⁻³ atm, which is higher than that of SCY (2.47 × 10⁻³ S cm⁻¹). Results also showed that SCY-YDC composite material exhibits higher ionic conductivity and lower electron-hole conductivity than SCY. Electron-hole transference number for SCY-YDC is 0.049 at 800 °C in pO₂ = 0.21 atm and pH₂O = 0.038 atm. Ultraviolet–visible spectrophotometry results provided evidence that SCY-YDC can suppress electron conduction.     

Influence of sintering aids and excess Lithium on the conductivity of perovskite-type Li3/8Sr7/16Zr1/4Nb3/4O3 solid electrolyte

Perovskite-structured Li_3/8Sr_7/16Zr_1/4Nb_3/4O₃ solid-state Lithium-conductors were prepared by conventional solid-state reaction method. Influence of sintering aids (Al₂O₃, B₂O₃) and excess Lithium on structure and electrical properties of Li_3/8Sr_7/16Zr_1/4Nb_3/4O₃ (LSNZ) has been investigated. Their crystal structure and microstructure were characterized by X-ray diffraction analysis and scanning electron microscope, respectively. The conductivity and electronic conductivity were evaluated by AC-impedance spectra and potentiostatic polarization experiment. All sintered compounds are cubic perovskite structure. Optimal amount of excess Li₂CO₃ was chosen as 20 wt% because of the total conductivity of LSNZ-20% was as high as 1.6×10⁻⁵ S cm⁻¹ at 30 °C and 1.1×10⁻⁴ S cm⁻¹ at 100 °C, respectively. Electronic conductivity of LSNZ-20% is 2.93×10⁻⁸ S cm⁻¹, nearly 3 orders of magnitude lower than ionic conductivity. The density of solid electrolytes appears to be increased by the addition of sintering aids. The addition of B₂O₃ leads to a considerable increase of the total conductivity and the enhancement of conductivity is attributed to the decrease of grain-boundary resistance. Among these compounds, LSNZ-1 wt%B₂O₃ has lower activation energy of 0.34 eV and the highest conductivity of 1.98×10⁻⁵ S cm⁻¹ at 30 °C.     

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.     

Effect of sintering temperature on the structural,electrical and electrochemical properties of novel Mg0.5Si2 (PO4)3 ceramic electrolytes

The objective of the present study is to investigate the effect of sintering temperature on the structural, electrical and electrochemical properties of novel Mg_0.5Si₂ (PO₄) ₃ NASICON structured compound prepared via sol gel method. X-ray diffraction was used to study the structural properties such as crystalline phase and lattice parameters of the solid electrolytes. Electrical properties of the compound were measured using impedance spectroscopy while the electrochemical stability was investigated by linear sweep voltammetry. All the sintering temperatures yielded compounds consisted of monoclinic crystalline phase with a space group of P1 2₁/c1. Lattice parameters for Mg_0.5Si₂ (PO₄) ₃ samples increased from the sintering temperature at 700–800 °C but decreased for sintering temperature at 900 °C. The sample sintered at 800 °C showed the highest total conductivity of 1.83×10⁻⁵ S cm⁻¹ and the highest value of ions mobility, µ of 6.17×10¹⁰ cm² V⁻¹ s⁻¹ which was attributed to the optimum size of migration channel indicated by its unit cell volume. Linear sweep voltammetry result showed that the Mg_0.5Si₂ (PO₄)₃ powder was electrochemically stable up to 3.21 V.     

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).     

Densification and electrical conductivity of Fe and Mn-doped Ce0.83Sm0.085Nd0.085O2-& by solid-liquid method

Fe and Mn-doped Ce_0.83Sm_0.085Nd_0.085O_2-& (SNDC) powders are successfully synthesized by the simple and efficient solid-liquid method. The crystallinity and morphologies of the powders were characterized by X-ray diffractometer, Raman spectrum, and scanning electron microscopy. The effect of doping on sintering behavior, grain interior, and grain boundary conductivity are studied. The doping of Fe can effectively reduce the sintering temperature from 1450^oC to 1250°C and keep the same density. Compared with SNDC, 1 mol% Fe-doped SNDC (Fe-SNDC) sintered at 1250°C shows a higher total conductivity of 2.13 × 10⁻² S·cm^-1 at 650°C. Also, it exhibits that doping of Fe can increase the conductivity of grain interior and grain boundary simultaneously. The present work shows that the Fe-SNDC synthesized by solid-liquid method can be used as a potential electrolyte for intermediate-temperature solid oxide fuel cells.     

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 and electrical properties of Ce1−xGdxO2−x/2 (x = 0.05–0.3) solid solutions prepared by a citrate–nitrate combustion method

Ce_1?xGd_xO_2?x/2 (GDC) powders with different Gd³⁺ contents (x = 0.05–0.3) were prepared by a simple citrate–nitrate combustion method. The influence of the Gd³⁺ doping content on the crystal structure and the electrical properties of GDC were examined. Many analysis techniques such as thermal analysis, X-ray diffraction, nitrogen adsorption analysis, scanning electron microscopy and AC impedance analysis were employed to characterize the GDC powders. The crystallization of the GDC solid solution occurred below 350 °C. The GDC powders calcined at 800 °C showed a typical cubic fluorite structure. The lattice parameter of GDC exhibited a linear relationship with the Gd³⁺ content. As compared with that sintered at other temperatures, the GDC pellet that sintered at 1300 °C had a high relative density of 97%, and showed finer microstructure. The conductivity of GDC was firstly increased and then decreased with the increase of the Gd³⁺ content. The sintered GDC sample with the Gd³⁺ content of 0.25 exhibited the highest conductivity of 1.27 × 10^?2 S cm^?1 at 600 °C.     

Effect of carbon content on electrical,thermal, and mechanical properties of porous SiC ceramics with B4C and C additives

The electrical, thermal, and mechanical properties of porous SiC ceramics with B₄C-C additives were investigated as functions of C content and sintering temperature. The electrical resistivity of porous SiC ceramics decreased with increases in C content and sintering temperature. A minimal electrical resistivity of 4.6 × 10^?2 Ω·cm was obtained in porous SiC ceramics with 1 wt% B₄C and 10 wt% C. The thermal conductivity and flexural strength increased with increasing sintering temperature and showed maxima at 4 wt% C addition when sintered at 2000 °C and 2100 °C. The thermal conductivity and flexural strength of porous SiC ceramics can be tuned independently from the porosity by controlling C content and sintering temperature. Typical electrical resistivity, thermal conductivity, and flexural strength of porous SiC ceramics with 1 wt% B₄C-4 wt% C sintered at 2100 °C were 1.3 × 10^?1 Ω·cm, 76.0 W/(m·K), and 110.3 MPa, respectively.     

Enhanced grain boundary ionic conductivity of LiTa2PO8 solid electrolyte by 75Li2O-12.5B2O3-12.5SiO2 sintering additive

LiTa₂PO₈(LTPO) has low electrolyte density and many pores at grain boundaries, and it is easy to precipitate dielectric phase LiTa₃O₈ at grain boundaries. The performance can be improved by adding 75Li₂O-12.5B₂O₃-12.5SiO₂ (LBS) sintering additive with low melting point during sintering. The effects of LBS addition on the microstructure and grain boundary ionic conductivity of LTPO electrolytes were studied. The results showed that the addition of LBS sintering additives reduced the sintering temperature, improved the density and stability of LTPO electrolyte samples, effectively inhibited the precipitation of LiTa₃O₈ phase, reduced the grain boundary impedance of samples, and improved the total ionic conductivity of electrolytes. When LBS was added at 0.4 wt%, the relative density of LTPO reached 93.54%, the grain boundary impedance decreased from 1243 Ω to 248.2 Ω, the total ionic conductivity increased from 1.55 × 10⁻⁴ S cm⁻¹ to 6.51 × 10⁻⁴ S cm⁻¹, and the ionic activation energy was 0.137 eV.     

Phase interaction and oxygen transport in La0.8Sr0.2Fe0.8Co0.2O3–(La0.9Sr0.1)0.98Ga0.8Mg0.2O3 composites

Composite ceramics made of two perovskite-type compounds, (La_0.9Sr_0.1)_0.98Ga_0.8Mg_0.2O_3−δ (LSGM) and La_0.8Sr_0.2Fe_0.8Co_0.2O_3−δ (LSFC) mixed in the ratio 60:40 wt.%, possess relatively high oxygen permeability limited by both bulk ionic conduction and surface exchange at 700−950 °C. Sintering at elevated temperatures (1320–1410 °C) necessary to obtain dense materials leads to fast interdiffusion of the components, forming almost single perovskite phase ceramics with local inhomogeneities. This phase interaction decreases the oxygen ionic transport in the composites, where the level of ionic conductivity is intermediate between those of LSGM and LSFC. The scanning electron microscopy (SEM) suggests a presence of Ga-enriched domains, probably having a high ionic conductivity. The size and concentration of these domains can be increased by decreasing sintering temperature or using preliminary coarsened LSGM powders. The maximum oxygen permeability is thus observed for the composite prepared under minimum sintering conditions sufficient to obtain gas-tight ceramics, including the use of LSGM, preliminary passivated at 1150 °C, and sintered at 1320 °C. The activation energy values for total conductivity, which is predominantly p-type electronic and slightly decreases due to component interaction, vary in the narrow range from 24.0 to 26.2 kJ/mol at 25–575 °C. The average thermal expansion coefficients (TECs) of LSGM-LSFC composites, calculated from dilatometric data in air, are (12.4–13.5)×10⁻⁶ K⁻¹ at 100–650 °C and (17.8–19.8)×10⁻⁶ K⁻¹ at 650–1000 °C.     

SDC-SCFZ dual-phase ceramics: Structure,electrical conductivity,thermal expansion,and O2 permeability

New CO₂-resistant dual-phase Sm_0.2Ce_0.8O_1.925–SrCo_0.4Fe_0.55Zr_0.05O_3-δ (SDC-SCFZ) ceramics present a promising outlook for potential future applications in membrane reactors and solid oxide fuel cells. Their high oxygen permeation flux and stability in CO₂ sweep gas also allow their integration in oxyfuel combustion. Here the structural characteristics, electrical conductivities, thermal expansion behaviors, and oxygen permeabilities of four different SDC-SCFZ membranes with weight ratios of 10:90, 25:75, 50:50, and 75:25 (SDC:SCFZ) are systematically studied. Among these four SDC-SCFZ compositions, 0.6 mm-thick 25 wt% SDC-75 wt% SCFZ displayed the highest oxygen permeation fluxes that reach 1.26 mL min⁻¹ cm⁻² at 950°C and retained its phase integrity under alternating He and CO₂ sweep gas over 72 hours of operation. This composite also showed a moderate thermal expansion coefficient of 1.90 × 10⁻⁵ K⁻¹ between 30°C and 1000°C and an electrical conductivity of at least 16 S cm⁻¹ at 550°C and above. Modeling studies revealed that the oxygen permeation fluxes through 25SDC-75SCFZ are limited by surface exchange reactions from 700°C to 800°C and mixed bulk diffusion and surface exchange reactions above 800°C.