Conductivity Of Pellets Research Articles

Developing High-Purity Sodium Oxychloride Solid-State Electrolyte for Sodium-Ion Batteries

Sodium-ion batteries have attracted significant attention as an alternative energy source to lithium-ion batteries. Solid-state sodium oxyhalides (Na3OX, X = Cl, Br, I) have the advantages of easy synthesis from cheap raw materials. In this study, sodium oxychloride (Na3OCl) antiperovskite was synthesized using a microwave furnace, the first instance in currently available literature. Using the microwave furnace also significantly decreased the reaction time when compared to other published procedures. The ionic conductivity of Na3OCl pellets was determined using electrochemical impedance spectroscopy (EIS). Na3OCl was hot pressed between sodiated hard carbon in a PEEK lined split cell with stainless steel current collectors. The symmetric cell was tested at room temperature with varying external pressures (1 MPa to 12 MPa). Symmetric cells were also tested at constant external pressure (6 MPa) from room temperature to 80˚C.Arrhenius plots demonstrated linear behavior in the whole temperature range with a calculated activation energy of 0.98 eV. The melting and crystallization temperatures were determined using differential scanning calorimetry (DSC). The purity of as-synthesized Na3OCl was evaluated using x-ray diffraction (XRD). The results on chemical composition and crystal-to-glass phase transformations were produced from in-situ X-ray diffraction (XRD) spectroscopy in the temperature range from 25˚C up to the melting point of Na3OCl. Cross-sectional SEM images of the Na3OCl pellets showed regions that were dense, but also regions with many pores (≤ 5 μm). SEM also showed microcracks that ranged from 1-5 μm. Future work will investigate methods of minimizing pores and microcracks during the cell manufacturing process as these surface features can impede efficient ionic movement.

Electrical and microstructural characteristics of GDC electrolyte synthesised by benzoate coprecipitation for solid oxide fuel cells

Gadolinium-doped ceria (GDC) is a promising electrolyte material for developing solid oxide fuel cells (SOFCs) because it offers a higher ionic conductivity at the intermediate operating temperature. In this work, nanocrystalline GDC (Ce1-xGdxO2-x/2, where x = 0.1 and 0.2) powders were synthesised through a novel co-precipitation synthesis method (benzoate route) using ammonium benzoate as a low-cost precipitant. The effect of the synthesis route and processing variables (calcination temperatures and time) on the microstructural and electrical properties of the resulting GDC powder was studied systematically. Multiple GDC electrolyte pellets were fabricated by pressing the GDC powders, followed by sintering the samples at 1100 °C for 6 h. The ionic and electronic conductivity of the GDC pellets were measured in air using EIS at different temperatures (450–750 °C). Huggins' model was used to determine the ionic and electronic conductivity of the GDC pellets. The fabricated electrolyte pellets showed a high relative density of 98.31and 99.02 % for the pre-calcined non-washed and pre-calcined washed powders, respectively, with a crystal size lower than 12 nm. Among all samples, the GDC electrolyte pellet fabricated using the pre-calcined washed powder exhibited the highest ionic conductivity of 3.63E-01 S cm−1 at 750 °C and activation energy of 0.52 eV with an average crystal size of 7–8 nm. The results of this study help to understand and design more efficient ceramic fuel cells with controlled microstructure and compositions at a lower cost.

Harnessing Cold Sintering to Fabricate Composite Polymer Electrolytes - A Paradigm Shift in Organic-Inorganic Material Assembly

The development of composite electrolytes for all-solid-state batteries is an emerging field, but the creation of predominantly inorganic electrolytes remains challenging. In this study, Li6.25Al0.25La3Zr2O12 (Al-LLZO), a ceramic material selected for its high ionic conductivity (1 × 10−4 S.cm−1 at ambient temperature) was shaped by the cold-sintering process (CSP). The organic phase was synthesized by free-radical polymerization of two poly(ethylene oxide) methacrylate derivatives in the presence of lithium bis(trifluoromethanesulfonyl)imide salts (LiTFSI). The polymethacrylate network with dangling poly(ethylene oxide) (PEO) chains was thus obtained. This in situ polymerization allows the one-pot synthesis of the composite electrolyte during CSP. Remarkably, the ionic conductivity of the CSP pellet varied with the nature of the organic phase, ranging from 1 × 10−4 to 1 × 10−5 S.cm−1 for non-grafted and grafted TFSI anion on the PEO-based network, respectively. Additionally, the transport of Li+ remained unaffected by the inorganic material’s nature as long as it contained Li species. Furthermore, a significant enhancement of the ionic conductivity was observed in the composite pellet compared to the TFSI grafted network (10−5 to 10−7 S.cm−1, respectively). Electrochemical impedance spectroscopy measurements revealed changes in the Al-LLZO||PEO-based polymer interface during CSP with the formation of an interphase, confirmed by a low activation energy value (0.1 eV).

In-Situ Formed Electron Inhibitor Enabling Dendrite-free Garnet Electrolytes: A Case Study of Fumed Silica.

Ta-doped Li7 La3 Zr2 O12 (LLZTO) solid-state electrolytes (SEs) show great promise for solid-state batteries due to its high conductivity and safety. However, one of the challenges it faces is lithium dendrite propagation upon long-term cycling. To address this issue, we propose the incorporation of fumed silica (FS) at the grain boundaries of LLZTO to modify the properties of the garnet pellet, which effectively inhibits the dendrite growth. The introduction of FS has demonstrated several beneficial effects. Firstly, it reduces the migration barrier of lithium ions, which helps prevent dendrite formation and propagation. Additionally, FS reduces the electronic conductivity of the SEs pellet, suppressing the dendrite formation. Moreover, the formed lithium silicates from FS might also be acted as electron inhibitor, thus inhibiting the lithium dendrite growth upon cycling. By investigating the use of FS as a modifier in LLZTO-based electrolytes, our study contributes to advancing dendrite-free solid-state electrolytes and thus the development of high-performance all-solid-state batteries.

A novel class of ATF fuels with large grain size, enhanced thermophysical properties and oxidation resistance

Two strategies have been extensively employed to develop advanced accident tolerant fuels (ATF): improving thermal conductivity and producing large grain sized pellets. However, there are few reports on the simultaneous utilization of both strategies. In this work, we fabricated Mo–Cr alloy reinforced UO2 (UMC) composite pellet with both high thermal conductivity and large grain size by a simple in-situ alloying method for the first time. The average grain size of UO2 increased from 6 μm to 113 μm. Thermal conductivity of the UMC pellet (with 2 vol% Mo) at 1200 °C increased by 36.46% compared with pure UO2. The increase rate of thermal conductivity per 1 vol% dopant reached about 18%. The Mo–Cr alloy formed continuous micro-cell layer around UO2 particles. Such continuous micro-cell Mo–Cr alloy layer and increase of UO2 grain size both helped improve the thermal conductivity of UMC composite pellets. Thermal expansion coefficient of the UMC under the operating temperature decreased by 11.90% compared with pure UO2. The oxidation resistance of the UMC pellet under high temperature steam was also improved. This work provides a new strategy towards fabricating ATF with both high thermal conductivity and large grain size.

Cluster dynamics simulations of tritium and helium diffusion in lithium ceramics

Tritium (T) and He diffusion in LiAlO2 and LiAl5O8 phases influences the performance of tritium producing burnable absorber rods (TPBARs) by affecting the gas release, swelling and thermal conductivity of Li-bearing ceramic pellets. Frenkel pair defects and clusters created by irradiation can attract T and He interstitials and form clusters of the type HeixLi,HeixAl,HeixO,TixLi,TixAlandTixO,1≤x≤4 in a Li, Al or O vacancy site (notation denotes x He or T atoms in a 1 Li, 1 Al or 1 O vacant site). The concentration and mobility of each of these clusters collectively contribute to the diffusion of the He and T gases in LiAlO2 and LiAl5O8. In this work, free energy cluster dynamics simulations implemented in the Centipede code, are used to obtain the concentration and diffusivities of these clusters which are then used to calculate the total diffusivity of T and He gases in LiAlO2 and LiAl5O8. The results show that diffusivity of T is at least one order of magnitude higher in LiAlO2 as compared to that in LiAl5O8 whereas He diffusion is 2–13 orders of magnitude higher in LiAlO2 as compared to that in LiAl5O8. There is a higher concentration of highly diffusive species (T interstitials and Ti03Li for the case of tritium and Hei01Li, Hei02Li and Hei03Li for the case of He) in LiAlO2 than in LiAl5O8 which increase the total diffusion of T and He in LiAlO2.

Exploring the effects of Al and Si dopants on the accident tolerant fuels of UO2 pellets for light water reactor

This study investigates the potential of Al and Si dopants to enhance the performance of UO2 pellets used in accident tolerant fuel for light water reactors. These dopants are anticipated to improve the uranium loading level, fission product retention, and thermal conductivity of UO2 pellets, while preserving their neutronic performance. Utilizing first-principles calculations, this study analyzes the kinetics of UO2-Al and UO2-Si interactions, predicting the resulting compound types, compositions, properties, and doping techniques. The calculations consider the reaction products and their thermodynamic properties. The study proposes the use of uranium aluminide, uranium silicide, or uranium aluminum silicide (e.g., UAl3, USi, U3Si2, or U3Al2Si3) to fill the UO2 grain boundaries, as opposed to Al2O3 and SiO2. This could be achieved by synthesizing uranium aluminide and uranium silicide separately, and then mixing them with UO2.

Excitation-wavelength-dependent photoluminescence/electrical conductivity of copper oxide nanorods

This research work reports the synthesis of copper (II) oxide (CuO) nanoparticles using the wet chemical co-precipitation method. The synthesised nanoparticles were characterised using ultraviolet–visible spectroscopy, X-ray diffraction, field emission scanning electron microscopy with energy-dispersive X-ray spectroscopy and high-resolution transmission electron microscopy in terms of absorption, crystal structure and size, morphology and elemental composition, and particle size. The existence of functional groups was verified by Fourier transform infrared spectroscopy. The synthesised copper (II) oxide nanoparticles showed an absorption peak at 397 nm, and a Tauc’s plot study showed a band-gap energy of 3.2 eV. The effects of varied excitation energies – namely, 3.81 and 3.54 eV – on the emission spectra of rod-shaped nanoparticles were assessed through photoluminescence spectroscopy, and the release of red, orange, green, violet and yellow colours was observed. The voltage–current characteristics of nanoparticle pellets were measured using a two-probe technique. The increase in the direct-current electrical conductivity of pellets heated at 100 and 200°C was ascertained. Overall, this research work provides valuable insights into the electronic properties of copper (II) oxide nanoparticles, which could have potential applications in various fields such as catalysis and electronics.

Exploring Li-CO2 batteries with electrospun PAN-derived carbon nanofibers and Li1.4Al0.4Ti1.6(PO4)3 solid-state electrolyte

This study introduces a highly stable and conductive sodium super ionic conductor-type solid electrolyte, Li1.4Al0.4Ti1.6(PO4)3 (LATP), to address safety concerns and mesoporous-structured polyacrylonitrile (PAN)-derived carbon nanofibers (CNFs) as a cathode material, which has the advantages of high affinity and adsorption of CO2 gas. LATP, an inorganic solid electrolyte, was synthesized using a solution-based method and its structural properties were assessed using X-ray diffraction and Raman spectroscopy. The ionic conductivity of LATP pellets was approximately 5.87 × 10−4 S cm−1. The gas adsorption properties and pore size distributions of the electrospun PAN-derived CNFs were analyzed using the Brunauer-Emmett-Teller method. A fabricated Li-CO2 battery successfully operated for 50 cycles with a current density of 50 mA g−1 and a cut-off capacity of 500 mAh g−1. Finally, a post-mortem analysis of the Li-CO2 battery was conducted using field-emission scanning electron microscopy and Raman and X-ray photoelectron spectroscopy to examine the electrode degradation mechanism. The analysis indicated that Li2CO3 was produced by the electrochemical reaction in the Li-CO2 batteries, causing electrode degradation. Therefore, improving the sluggish kinetics of Li2CO3 decomposition using a catalyst embedded in PAN-derived CNFs will realize high-performance Li-CO2 batteries.

Insights into the Effects of Co-Regulated Factors on Li1.3Al0.3Ti1.7(PO4)3 Solid Electrolyte Preparation: Sources, Calcination Temperatures, and Sintering Temperatures.

The ionic conductivity, phase components, and microstructures of LATP depend on its synthesis process. However, their relative importance and their interactions with synthesis process parameters (such as source materials, calcination temperature, and sintering temperature) remain unclear. In this work, different source materials were used to prepare LATP via the solid-state reaction method under different calcination and sintering temperatures, and an analysis via orthogonal experiments and machine learning was used to systematically study the effects of the process parameters. Sintering temperatures had the greatest effect on the total ionic conductivity of LATP pellets, followed by the sources and calcination temperatures. Sources, as the foundational factors, directly determine the composition of a major secondary phase of LATP pellets, which influences the whole process. The calcination temperature had limited impact on the ion conductivity of LATP pellets if pellets were sintered under the optimal temperature. The sintering temperature is the most important factor that influences the ion conductivity by eliminating most secondary phases and altering the microstructure of LATP, including the intergranular contact, grain size, relative densities, etc. This work offers a novel perspective to comprehend the synthesis of solid-state electrolytes beyond LATP.

Fabrication and thermal conductivity of UN-UB2 composites fabricated by spark plasma sintering

The fabrication and thermal conductivity of mixed-phase UN-UB2 composite pellets has been investigated using the laser flash method. Composites were fabricated by synthesizing UB2 and UN via the carbo/borothermic reduction and hydriding-nitriding-denitriding routes respectively, followed by spark plasma sintering of pellets at 1973 K. Combustion analysis of the synthesized powder showed the existence of C impurity in the synthesized UN. A U-B-N ternary phase formed during SPS fabrication, as an interaction product between the UN and UB2. Analysis of the thermal diffusivity of the composites indicated the partial oxidation of the composites during measurements. The corrected thermal conductivity of the composites was found to increase with increasing UB2 content up to 1073 K (maximum temperature measured). The fabricated composites showed a higher thermal conductivity than the reported UN at low temperatures (673 K). However, the increase was less significant at higher temperatures and the thermal conductivity was found to be lower than UN for composites with low UB2 content (up to 10 wt.%), potentially due to impurities within the synthesised UN.

Terahertz conductivity of iron oxide-graphene oxide composite pellet

Electrical and optical characteristics of materials are the most used physical properties that serve as tools to identify and analyze certain dynamics of matter being studied. In this paper, the optical parameters of iron oxide-graphene oxide composite mixed with polyethylene were characterized using terahertz time domain spectroscopy (THz-TDS) and impedance spectroscopy. The real and imaginary conductivities were obtained from impedance measurements in the low frequency range. The complex refractive index and absorption coefficient were also determined using THz-TDS. From these quantities, the complex conductivity of the sample was determined and was fitted using the combined Drude-Smith Lorentz model.

Grain Engineering for High-Performance Garnet-Type Li7La3Zr2O12 Solid Electrolytes

Garnet-type solid electrolytes based on cubic Li7La3Zr2O12 (LLZO) are promising candidates for the development of Li metal solid-state batteries due to their high ionic conductivity and excellent chemical stability against metallic lithium. Unfortunately, the leakage of electron through the interface and grain boundaries leads to the nucleation of Li dendrite inside solid electrolyte, making it easier for the failure of solid-state Li metal batteries. Here, we introduce a promising fluorination strategy to suppress Li dendrite formation by blocking electron transport through the interface and along the grain boundaries. Fluorination not only decreases the electronic conductivity of garnet pellet but also improves its wettability toward Li metal. As a result, the optimized LLZOge pellet demonstrates an outstanding critical current density of 2.7 mA cm‒2 and ensures ultra-long cyclability over 5000 h at 0.2 mA cm‒2 and over 300 h at 1 mA cm‒2 at room temperature. This work demonstrates the efficacy of the fluorination strategy in increasing the electronic resistance of garnet-type electrolyte for the suppression of Li dendrite growth. Figure 1

Synthesis and Thermal Evaporation Deposition of Sodium Oxychloride Solid-State Electrolyte for Sodium-Ion Batteries

Sodium-ion batteries have attracted significant attention by offering an alternative option to lithium-ion batteries. Solid-state sodium oxyhalides (Na3OX, X = Cl, Br, I) have the advantage of cost-effective synthesis from raw materials in a time-effective manner. In this study, sodium oxychloride (Na3OCl) antiperovskite was synthesized using a novel approach that allowed for facile synthesis outside of an argon glovebox. The ionic conductivity of Na3OCl pellets compressed between graphite-coated copper foil was tested in the temperature range of 160˚C and 200˚C using electrochemical impedance spectroscopy (EIS). Arrhenius plots demonstrated linear behavior in the whole temperature range with a calculated activation energy of 0.98 eV. At lower temperatures, EIS data was not available likely due to high impedance from the thickness of the electrolyte pellet, high activation energy, or slow migration of sodium ions through the Na3OCl structure. To decrease electrolyte thickness, we implement physical vapor deposition (PVD) thermal evaporation to coat thin films (<100 µm) of the electrolyte onto graphite-coated copper foil and sodium-based cathodes for use in symmetric cell and half-cell configurations. The melting and crystallization temperatures were determined using differential scanning calorimetry (DSC). The purity of as-synthesized sodium oxychloride and PVD-deposited layer was evaluated using X-ray diffraction (XRD). The results on chemical composition and crystal-to-glass phase transformations are produced from in-situ X-ray diffraction (XRD) spectroscopy in the temperature range from 25˚C up to the melting point of Na3OCl. Cross-sectional SEM images of PVD-deposited sodium oxychloride showed an even distribution of sodium, oxygen, and chlorine. However, XRD analysis of deposited layers showed that sodium oxychloride had a tendency to decompose into the precursors during deposition. This work is focused on maintaining the sodium oxychloride composition and structure during PVD thermal evaporation by optimizing the PVD deposition parameters.The authors acknowledge financial support from the NSF IUCRC program for the “Center for solid-state electric power storage” (#2052631) and support from the South Dakota Board of Regents for the “Governor’s Research Center (GRC) for electrochemical energy storage”.

Influence of powder properties and mixing technique under different conditions, on the densification and thermal conductivity of AlN for solar thermal applications

In this study, a novel approach is presented which can be utilized to enhance the thermal conductivity and densification of sintered AlN pellets. AlN pellets with a CaO additive were produced by spark plasma sintering. The influence of CaO powder properties such as particle size (micron-, submicron- and nano-scale), dispersion, flowability and structural characteristics, on the mixing behavior of AlN and CaO mixed powders, and on the porosity and thermal conductivity of AlN pellets, were investigated. Additionally, the influence of mixing conditions, including additive content and rotational speed in a novel high-shear mixer (Picomix), were studied and various mixing techniques were compared. The results indicate that when the CaO content of the AlN pellets is increased to 3 wt%, their thermal conductivity rises from 48.1 W/m·K to 112.9 W/m·K. This increase can be attributed to the formation of a liquid phase, and to a reduction in pellet porosity during sintering. Furthermore, when the rotational speed of the mixer is increased to 5000 rpm, the pellets’ thermal conductivity further rises to 126.2 W/m·K. This improvement is a result of the enhanced dispersion of CaO in the mixed powder. The shearing forces in the Picomix facilitate the coating of AlN particles with submicron- or nano-scale CaO particles, thereby improving the flowability of the mixed powder and narrowing the particle size distribution. This further improves the liquid phase distribution, thus enhancing the thermal conductivity of the AlN pellets (135.3 W/m·K). The novel high-shear mixer (Picomix) has demonstrated enhanced performance when compared with traditional mixing techniques (ball milling and manual mixing), since it involves a solvent-free process, is faster, has a lower energy consumption, causes less powder-oxidation and leads to a higher value of thermal conductivity, making it an excellent choice for the preparation of mixed powders for solar thermal applications.

Mixed analytical model to estimate the anisotropic effective thermal conductivity and in-reactor performance of metallic microcell UO2

A mixed analytical model is utilized to estimate the effective thermal conductivity of microcell UO2 pellets. The proposed model consists of a mixture of parallel and series structural models that collectively take into account the unique cell geometry of the anisotropic metal network and the corresponding fractional contribution to the heat flow. This relatively simple structure model can explain the anisotropy of the thermal conductivity of UO2-Mo microcells, as observed in both experimental tests and numerical calculations. The physics-based mixed analytical model allows us to accommodate the effects of the UO2 burnup and wall structure changes on the effective thermal conductivity of microcell UO2 pellets. To validate the model's ability to predict the burnup dependence, the reduced fuel centerline temperature in a UO2 -5vol% Cr microcell under irradiation was estimated at selected burnup levels and compared to the temperature evolution observed in a Halden reactor test, in which the sample pellets were irradiated up to 16MWd/kgU. The comparison demonstrated that the mixed analytical model suitably predicts the fuel temperature changes in irradiated UO2 -5vol% Cr microcells. The model proposed here is a preliminary type based on limited experimental data, and the parameters of the model could be modified further with the accumulation of more measurement data.

Progress and Perspectives of Lithium Aluminum Germanium Phosphate‐Based Solid Electrolytes for Lithium Batteries

AbstractSolid‐state lithium batteries are considered promising energy storage devices due to their superior safety and higher energy density than conventional liquid electrolyte‐based batteries. Lithium aluminum germanium phosphate (LAGP), with excellent stability in air and good ionic conductivity, has gained tremendous attention over the past decades. However, the poor interface compatibility with Li anode, slow Li‐ion conduction in thick pellets, and high‐temperature sintering procedure limit the further development of LAGP solid electrolytes in practical applications. This review comprehensively summarizes the crystal structure, Li‐ion conducting mechanism, and various synthesis methods, especially the latest thin‐film preparation approach. The underlying reason for Li/LAGP interfacial instability is identified, followed by several advanced interface engineering strategies, for example, introducing a functional interlayer. The integration design of LAGP‐based solid electrolytes and cathode is also highlighted to enable high‐loading cathodes. Additionally, recent progress of lithium‐oxygen and lithium‐sulfur batteries with LAGP‐based solid electrolytes is discussed. Moreover, the different Li‐ion migration pathways, preparation procedures, and electrochemical performance of polymer‐LAGP composite solid electrolytes in Li‐ion batteries are introduced. Lastly, the remaining challenges and opportunities are proposed to encourage more efforts in this field. This review aims to provide fundamental insights and promising directions toward practical LAGP‐based solid‐state batteries.

Thermal conductivity of UO2 pellets enhanced by a semi-continuous structure of Ti3SiC2

The current distribution structure of the thermal conductivity (TC) enhancements in UO2 matrix can be divided into three categories: dispersed structure, continuous structure and oriented structure. This paper develops a new semi-continuous structure to improve the TC of UO2. Ti3SiC2 is selected as the enhancement in this paper due to its excellent irradiation resistance and high TC at elevated temperature. The semi-continuous structure of Ti3SiC2 is formed through a simple centrifugal spheroidization of UO2 and a followed powder mixing process. Both the theoretical prediction and experimental results indicate the semi-continuous structure has a close TC enhancing efficiency to the continuous structure. Meanwhile, the semi-continuous structure has the advantages of simplifying the fabrication process and can be applied to more kinds of enhancements compared to the continuous structure. The TC of Ti3SiC2/UO2 is remarkably improved at elevated temperature compared with pure UO2, which is beneficial to the fuel safety.

Influence of transition or lanthanide metal doping on the properties of Sr0.6Ba0.4Ce0.9M0.1O3-δ (M = In, Pr or Ga) electrolytes for proton-conducting solid oxide fuel cells

Proton-conducting electrolytes offer an alternative electrolyte to replace the oxygen-ion conducting conventional electrolyte for solid oxide fuel cells (SOFCs). In this study, proton-conducting Sr0.6Ba0.4Ce0.9M0.1O3-δ (M = In, Pr, Ga) electrolytes without Zr were synthesized by the glycine-nitrate process for intermediate-temperature SOFC applications. The thermal decomposition and crystalline structure of the electrolyte powders were analysed by thermogravimetry (TG) analyses and X-ray diffraction (XRD), respectively. The morphological structure and chemical stability of the electrolyte pellets were examined by field-emission scanning electron microscopy (FESEM) and XRD. Electrochemical impedance spectroscopy (EIS) analysis was used to evaluate the proton conductivity of each electrolyte pellet at different operating temperatures (500–800 °C) in a gas mixture composed of hydrogen (10%) and nitrogen (90%) humidified at room temperature (wet H2/N2), air humidified at room temperature (wet air) and dry air. The ideal calcination temperature for the electrolyte is determined to be 1000 °C based on TGA and XRD analyses, which indicate a high degree of crystallization without any formation of secondary phases. Furthermore, the relative density of all sintered electrolyte pellets is found to lie within an acceptable range (>90%) for good ion conduction. The Sr0.6Ba0.4Ce0.9Ga0.1O3-δ electrolyte displays the highest relative density (99%). However, the chemical stability analysis shows that Sr0.6Ba0.4Ce0.9Pr0.1O3-δ is the most stable electrolyte with a small additional secondary phase. The EIS results indicate that the Sr0.6Ba0.4Ce0.9In0.1O3-δ electrolyte shows the highest ionic conductivities of 1.80 × 10-3, 2.26 × 10-3 and 1.28 × 10-3 S/cm at 700 °C in wet H2/N2, wet air and dry air, respectively. Overall, Sr0.6Ba0.4Ce0.9M0.1O3-δ doped with transition elements (In and Ga) are considered potential electrolytes for proton-conducting SOFCs. In terms of sinterability, chemical stability and proton conductivity, the Sr0.6Ba0.4Ce0.9In0.1O3-δ electrolyte doped with indium (In) is considered the best electrolyte in this work.

Effect of A-site modification on electrical properties and chemical stability of Ba1-xCaxCe0.5Zr0.3Y0.2O3-δ proton-conducting electrolyte

This article investigates the substitution effect of different Ca2+ concentrations at A-sites in perovskites like yttrium and zirconium co-doped with barium cerate. This study focuses on the electrical properties and chemical stability of synthesized materials. With the help of solid-state reaction, different variants of Ba1-xCaxCe0.5Zr0.3Y0.2O3-δ (with values of x being 0, 0.02, 0.05, and 0.1 in succession) were obtained, which are also referred to as BCxCZY (where x takes the values 0, 2, 5, and 10 one at a time) in forthcoming discussion. X-ray diffraction results indicate that the group of BCxCZY (with x = 0, 2, 5, and 10) was synthesized successfully, and according to the energy dispersive spectrometer, the second phases in BC5CZY and BC10CZY were observed. Combined with literature analysis, the second phase of BC5CZY and BC10CZY is determined as BaCa2Y5O12 and Y2O3, respectively. Scanning electron microscopy images illustrate that the density improved with increased Ca2+ concentration. BC2CZY and BC5CZY samples show better chemical stability in CO2 and humid atmospheres than Ca-free samples. It means chemical stability improves with the proper Ca2+ concentration. The alternating current (AC) impedance analysis obtained the conductivities of electrolyte pellets in various atmospheres and temperatures. The total conductivities (σtot) of Ca-substituted BCxCZY pellets are lower than that of unsubstituted BCZY pellets and decrease with increased Ca2+ concentration. The defect equilibria model was utilized to calculate the partial conductivities. The results show that the proton conductivity of each sample is nearly constant at pH2O = 0.024 atm and pO2 = 0.2 atm. The transference numbers of protons are dominated in 500–750 °C temperature regions and increase with the Ca2+ concentration. In a low pH2O atmosphere, BC10CZY exhibits conductivity with both electron holes (h∙) and oxide ions (vO∙∙). In contrast, at high pH2O values, the primary carriers are protons (OHO∙). The total conductivities of Ca-substituted pellets decrease with an increase in proton transference number.