High Sintering Research Articles

Lithium Tracer Diffusion in LixCoO2 and LixNi1/3Mn1/3Co1/3O2 (x = 1, 0.9, 0.65)-Sintered Bulk Cathode Materials for Lithium-Ion Batteries

The knowledge of Li diffusivities in electrode materials of Li-ion batteries (LIBs) is essential for a fundamental understanding of charging/discharging times, maximum capacities, stress formation and possible side reactions. The literature indicates that Li diffusion in the cathode material Li(Ni,Mn,Co)O2 strongly increases during electrochemical delithiation. Such an increased Li diffusivity will be advantageous for performance if it is present already in the initial state after synthesis. In order to understand the influence of a varying initial Li content on Li diffusion, we performed Li tracer diffusion experiments on LixCoO2 (LCO) and LixNi1/3Mn1/3Co1/3O2 (NMC, x = 1, 0.9, 0.65) cathode materials. The measurements were performed on polycrystalline sintered bulk materials, free of additives and binders, in order to study the intrinsic properties. The variation of Li content was achieved using reactive solid-state synthesis using pressed Li2CO3, NiO, Co3O4 and/or MnO2 powders and high temperature sintering at 800 °C. XRD analyses showed that the resultant bulk samples exhibit the layered LCO or NMC phases with a low amount of cation intermixing. Moreover, the presence of additional NiO and Co3O4 phases was detected in NMC with a pronounced nominal Li deficiency of x = 0.65. As a tracer source, a 6Li tracer layer with the same chemical composition was deposited using ion beam sputtering. Secondary ion mass spectrometry in depth profile mode was used for isotopic analysis. The diffusivities followed the Arrhenius law with an activation enthalpy of about 0.8 eV and were nearly identical within error for all samples investigated in the temperature range up to 500 °C. For a diffusion mechanism based on structural Li vacancies, the results indicated that varying the Li content does not result in a change in the vacancy concentration. Consequently, the design and use of a cathode initially made of a Li-deficient material will not improve the kinetics of battery performance. The possible reasons for this unexpected result are discussed.

Densification of hydroxyapatite/zirconia nanocomposites fabricated via low-temperature mineralization sintering process and their mechanical properties

Hydroxyapatite/zirconia (HAP/ZrO2) composites were fabricated via the low-temperature mineralization sintering process (LMSP) at an extremely low temperature of 130 °C to enhance the mechanical properties of HAP and broaden its practical applications. For this purpose, 5–20 vol% calcia-stabilized ZrO2 were introduced into HAP, and HAP/ZrO2 nanoparticles, mixed with simulated body fluid, were densified under a uniaxial pressure of 800 MPa at 130 °C. At 10 vol% ZrO2, the relative density of the HAP/ZrO2 composite was determined to be 88.3 ± 1.1%. Additionally, it exhibited the highest values of mechanical properties such as the Vickers hardness (3.68 ± 0.18 GPa), fracture toughness (1.11 ± 0.10 MPa·m1/2), biaxial flexural strength (63.72 ± 2.35 MPa), and Young’s modulus (83.91 ± 1.93 GPa) among the composite samples. These values were considerably higher than those of the pure HAP matrix due to the adequate reinforcement by ZrO2 nanoparticles. Notably, owing to the low sintering temperature, phase decomposition of HAP, normally observed at high sintering temperatures above 1200 °C, was not observed. These results suggest that LMSP enables the incorporation of reinforcing ceramic materials with high sintering temperatures into bioactive materials at significantly lower temperatures, thereby improving their properties.

Efficient Catalysis for Zinc-Air Batteries by Multiwalled Carbon Nanotubes-Crosslinked Carbon Dodecahedra Embedded with Co-Fe Nanoparticles.

The design and fabrication of nanocatalysts with high accessibility and sintering resistance remain significant challenges in heterogeneous electrocatalysis. Herein, a novel catalyst is introduced that combines electronic pumping with alloy crystal facet engineering. At the nanoscale, the electronic pump leverages the chemical potential difference to drive electron migration from one region to another, separating and transferring electron-hole pairs. This mechanism accelerates the reaction kinetics and improves the reaction rate. The interface electronic structure optimization enables the CoFe/carbon nanotube (CNT) catalyst to exhibit outstanding oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) performance. Specifically, this catalyst achieves an ORR half-wave potential (E₁/₂) of 0.895V, outperforming standard Pt/C and RuO₂ electrocatalysts in terms of both specific activity and stability. It also demonstrates excellent electrochemical performance for OER, with an overpotential of only 287mV at a current density of 10mA cm⁻2. Theoretical calculations reveal that the carefully designed crystal facets reduce the energy barrier of the rate-determining steps for both ORR and OER, optimizing O₂ adsorption and promoting the oxygen capture process. This study highlights the potential of developing cost-effective bifunctional ORR-OER electrocatalysts, offering a promising strategy for advancing Zn-air battery technology.

Effects of La2Ce2O7 on the phase composition, microstructure, wetting behaviour and corrosion resistance of magnesia refractory

The addition of rare earth oxides has a significant impact on the improvement of thermal properties of refractory materials. Magnesia refractory with La2Ce2O7 was prepared by high-temperature solid-phase synthetic sintering at 1873 K for 5h using fused magnesia as raw materials, CeO2 and La2O3 as addition, respectively. The effect of La2Ce2O7 on the phase composition, microstructure, apparent porosity, bulk density, wetting behaviour and corrosion resistance with steel of fused magnesia were investigated. When the content of La2Ce2O7 was 20wt%, the results showed that as-prepared samples from fused magnesia with an apparent porosity of 17.63% and a bulk density of 3.11g·cm-3 were obtained by high temperature solid-phase sintering reaction at 1873 K for 5h, respectively. Due to the addition of La2Ce2O7, and raw materials in the impurity phase CaO and SiO2 for the reaction, the generation of a small amount of CaLa4(SiO4)3O and La8.89Si6O25.9 high melting point phase, plugging the air holes, thus improving the bulk density of the fused magnesia and reduce its apparent porosity. The ability of steel corrosion of as-prepared samples from fused magnesia doped with La2Ce2O7 have better resistance than conventional fused magnesia, which the thickness of the corrosion layer was reduced by 42.1% compared to as-prepared samples without La2Ce2O7.

Impact of sintering temperature and KMnO4 addition on the growth of Bi2212 ceramics

In this study, the highest volume fraction was obtained by the combined effect of KMnO4 doping and different sintering temperatures (840 and 850 °C). Bi2Sr2CaCu2(KMnO4)xO8+δ compounds with x = 0, 0.01, 0.03, 0.05 and 0.07 were prepared by the conventional solid-state reaction method. The phase composition and microstructure were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and Raman Spectroscopy. The XRD phase study showed that the optimum sintering temperature was 850 °C with a KMnO4 doping concentration of 0.05. With increased doping (x), the texture of Bi2212 became more crystalline, with a grain growth preference along the (00l) direction. It is clear that the rate of formation of the Bi2212 phase is favored by high sintering temperature and addition of KMnO4. The line intensities of the Bi-2212 phase were found to increase significantly with KMnO4 addition up to the critical value of x = 0.01 and the cell structure volume is seen to decrease with increasing doping rate. This may be attributed to inhomogeneities in oxygen concentration This indicates that the sintering temperature has a strong influence on the structural and morphological properties. As reported in the literature, the Raman modes at 489.76 cm-1 and 630 cm-1 are associated with the vibrations of O(3)BiA1g and O(2)SrA1g along the c axis for the Bi-2212 phase. The A1g modes are symmetric for vibrations of Bi, Sr, Ca, Cu, OBi, OSr and OCu along the c axis.

High Speed Sintering of Polyamide 12: From Powder to Part Properties.

High Speed Sintering (HSS) is an additive manufacturing process with great potential to produce complex, high-quality polymer parts on an industrial scale. However, little information is currently available on the characteristics of the powder materials used and the part properties that can be achieved. This is also the case for the standard material polyamide 12 (PA 12) and the first commercially available HSS machine, the VX200 HSS. The aim of this study is, therefore, to provide the first comprehensive overview of the properties of PA 12 parts manufactured with the VX200 HSS and the characteristics of the PA 12 powder. This includes the analysis of the influence of part orientation and part position in the build job. To characterize the powder, particle size distribution, particle shape, thermal properties and powder flowability were analyzed. To characterize the parts, density and various thermal, mechanical and geometrical properties were analyzed. In summary, the powder material and part properties are largely similar to those of other Powder Bed Fusion of Polymer (PBF/P) processes. However, there are also significant differences for some part properties. It was also determined that the anisotropy of parts is very low compared to that of many other additive manufacturing processes.

An Enhanced Bioactive Glass Composition with Improved Thermal Stability and Sinterability.

The development of new bioactive glasses (BGs) with enhanced bioactivity and improved resistance to crystallization is crucial for overcoming the main challenges faced by commercial BGs. Most shaping processes require thermal treatments, which can induce partial crystallization, negatively impacting the biological and mechanical properties of the final product. In this study, we present a novel bioactive glass composition, S53P4_MSK, produced by a melt-quench route. This novel composition includes magnesium and strontium, known for their therapeutic effects, and potassium, recognized for improving the thermal properties of bioactive glasses. The thermal properties were investigated through differential thermal analysis, heating microscopy and sintering tests from 600 °C to 900 °C. These characterizations, combined with X-ray diffraction analysis, demonstrated the high sinterability without crystallization of S53P4_MSK, effectively mitigating related issues. The mechanical properties-elastic modulus, hardness and fracture toughness-were evaluated on the sintered sample by micro-indentation, showing high elastic modulus and hardness. The bioactivity of the novel BG was assessed following Kokubo's protocol and confirmed by scanning electron microscopy, X-ray energy dispersive spectroscopy, and Raman spectroscopy. The novel bioactive glass composition has shown high sinterability without crystallization at 700 °C, along with good mechanical properties and bioactivity.

Sintering model for predicting distortion of additively manufactured complex parts

PurposeThis study aims to provide understanding of the influence of external factors, such as gravity, during sintering of three dimensional (3D)-printed parts in which the initial relative density and cohesion between the powder particles are lower compared with those present in the green parts produced by traditional powder technologies. A developed model is used to predict shrinkage and shape distortion of 3D-printed powder components at high sintering temperatures.Design/methodology/approachThree cylindrical shape connector geometries are designed, including horizontal and vertical tubes of different sizes. Several samples are manufactured by binder jetting to validate the model, and numerical results are compared with the measurements of the sintered shape.FindingsSimulations are consistent with empirical data, proving that the continuum theory of sintering can effectively predict sintering deformation in additively manufactured products.Originality/valueThis work includes the assessment of the accuracy and limits of a multiphysics continuum mechanics–based sintering model in predicting gravity-induced distortions in complex-shaped additively manufactured components.

Sintering of copper nanoparticles using intense pulsed light for screen-printed films on flexible substrate

Abstract Rapid growth in applications involving large area flexible electronics has led to wide adoption of the technique of sintering printed films using intense pulsed light due to its pulse mode operation and ability to reach high sintering temperatures without affecting the underlying substrate significantly. We study the sintering mechanisms of screen-printed thin films of copper nanoparticles on polyethylene terephthalate plastic substrates by varying the irradiance energy over a wide range to monitor conductivity and associated microstructure changes. We obtain optimized parameters which indicate the existence of a sharp threshold irradiance energy to kickstart sintering, and two distinct regimes beyond that. The low temperature regime has a high energy barrier while the high temperature regime has a substantially reduced energy barrier with a change of phase due to local melting.

Enhanced ionic conductivity in Na3Zr2Si2PO12 solid electrolyte via glass addition with low sintering temperature

NZSP (Na3Zr2Si2PO12) stands as a pivotal category of solid-state electrolyte materials in emerging energy devices like solid-state sodium ion batteries (SSSIBs) and solid-state supercapacitors (SSSCs), primarily due to its commendable ionic conductivity at room temperature. However, the high sintering temperatures required to achieve high densities limit the process conditions for applications and increase the energy consumption of the manufacturing process. In this work, we optimized the sintering temperature and obtained high ionic conductivity by incorporating a SiO2-Al2O3-CaO-B2O3 (SACB) glass into NZMSP (Na3.5Zr1.75Mg0.25Si2PO12) ceramics. The results showed that the fluxing of low melting SACB glass increased the cell volume and the bulk density in the matrix material, leading to a significant increase in the grain boundary conductivity of NZMSP. The synthesized ceramic samples (x = 2.1 wt%) maintains high total ionic (∼ 1.65 × 10−3 S/cm) and low electronic conductivities (< 2 × 10−8 S/cm). This work insights into the key role of glass additives in enhancing the properties of sodium ionic conductors, thereby paving the way for the evolution of more efficient and cost-effective processes in advanced ceramic materials.

Two-step preparation and characterization of Bi-2212 superconductors by the glycine-nitrate method

In order to prepare high-quality sub-stable copper oxide superconductor Bi-2212, the glycine-nitrate method combined with rapid sintering process was used in this paper. Firstly, the glycine-nitrate method was used to obtain highly active Bi-2212 precursor powders with uniform composition, and then Bi-2212 superconductor powders were prepared by rapid sintering. Glycine acted as a combustion agent while giving property of the complexation to ensure the homogeneity of multiple chemical components. The high-quality precursor powder was the basis for broadening the temperature interval of the pure phase of Bi-2212. And then the effects of precursor powder sampling pressure on Bi-2212 superconducting materials were systematically investigated. On this basis, the pure-phase temperature interval of Bi-2212 superconducting materials prepared by the nitroglycerin method was further investigated. The results showed that the increase of the sample preparation pressure can effectively optimize the crystallinity of Bi-2212, which no longer changed significantly after 300 MPa. The pure phase temperature interval of Bi-2212 was 830–880 °C. The samples showed the characteristic lamellar morphology. The optimum sintering temperature was 850°C. The crystal integrity of Bi-2212 was destroyed under high temperature sintering conditions, and the two-dimensional properties were enhanced. The superconducting properties of Bi-2212 were acceptable, with a Tc, onset of 82.1 K, Tc, zero of 72.4 K, and ΔTc of 9.7 K. This work largely reduces the difficulty in the preparation of the superconductors of Bi-2212, and it provides a good basis for the preparation of multi-component functional oxides by using the nitrate method.

Hydrotalcite-derived well-dispersed and thermally stable cobalt nanoparticle catalyst for ammonia decomposition

Ammonia is a carbon-free hydrogen carrier, and development of non-noble metal catalyst to decompose ammonia into hydrogen is desirable for practical applications. However, the metal catalyst is challenged by the sintering of metal particles under high-temperature reaction conditions. In this study, a series of Li-, Al-, and Co-containing hydrotalcite-like compounds (HTlc) were synthesized by co-precipitation and used as precursors to prepare well-dispersed and thermally stable Co nanoparticle catalysts for ammonia decomposition. The obtained precursors and catalysts were characterized by means of X-ray powder diffraction (XRD), temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), and so on. All of the precursors formed hydrotalcite-like phase, which consisted of Li–Al–(Co) HTlc and/or Co–Al HTlc dependent on the Co content. Upon calcination at 500 °C, HTlc decomposed into an Al-substituted Co3O4 spinel oxide, as confirmed by two distinctly separated reduction steps in H2-TPR. Following reduction at 700 °C, well-dispersed Co metal nanoparticles with an average particle size of ∼9.2–12.4 nm were obtained. It was suggested that the incorporation of Al3+ into Co3O4 led to a strong interaction between cobalt and aluminum, which suppressed the crystal growth of Co3O4 and the sintering of Co metal during the thermal treatments, resulting in good Co dispersion. The optimal LiAlCo(1.5) catalyst showed superior activity than that prepared by impregnation method, giving almost complete conversion of ammonia at 575 °C under a space velocity of 5,000 mL gcat–1 h–1. More importantly, this catalyst maintained stable activity at 625 °C for 100 h, exhibiting high stability and sintering resistance. The good catalytic performance was attributed to the high Co metal dispersion and strong metal–support interaction benefiting from the uniform distribution of cobalt in the HTlc precursor. These results demonstrate the applicability of HTlc to the preparation of metal catalysts with improved dispersion and thermal stability.

Dense and uniform Mo10W alloy prepared by combining a vacuum sintering process with a hot-pressing process

Mo10W billets are fabricated via vacuum sintering (VS), hot pressing (HP), and VS + HP process. The results show that the Mo10W prepared by VS has good uniformity, even when the sintering temperature is as low as 1600 °C. However, the relative density of this alloy is only 95.37% when the sintering temperature is increased to 1900 °C. A high sintering temperature coarsens the grains. The relative density of HP-based Mo10W reaches 99.05% after sintering at 1500 °C, but its distributions of Mo and W are uneven. The Mo and W distributions of the VS + HP Mo10W alloy are uniform and its relative density reaches 98.1%. This work provides a new method for simultaneously improving the uniformity and density characteristics of Mo alloys.

Ionic Conductivity of Anisotropically Sintered Apatite-Type Lanthanum Silicon Oxide

Apatite-type lanthanum silicon oxide (LSO) has attracted keen attention as one of the new solid electrolytes for its high oxygen ionic conductivity. LSO has a hexagonal apatite structure with oxygen sites coordinated along the c-axis direction and exhibits higher ionic conductivity in the c-axis direction than that of yttria stabilized zirconia, which has been put to practical use as a solid electrolyte. However, to fabricate a dense sintered body with LSO single phase, high sintering temperature of around 1700 ℃ is required due to its very small diffusivity of La and Si. From a practical standpoint, it is necessary to develop a process to lower the sintering temperatures and foster orientation along the c-axis direction to realize practice use of LSO as solid electrolytes.In this study, a powder coated with silicon oxide (SiO2) on the surface of lanthanum oxide (La2O3) powder was prepared for the purpose of completing the diffusion of La and Si at an early stage in sintering. This coated powder is noted as additive-free LSO. Further, a powder doped with tetrafluoroboric acid was also prepared for the purpose of lowering the sintering temperature by enhancing the diffusion of La and Si. This doped powder is noted as added LSO. Sintering behaviors of each powder, crystal phases and ionic conductivities of the obtained sintered bodies were measured.The experimental procedure is as follows. La2O3 powder and tetraethoxysilane (TEOS) were weighed to be La9.33Si6.00O26 and mixed in ethanol followed by dripping 10% ammonia water up to the pH of 10 in the mixed solution. Additive-free LSO was obtained by drying the mixed solution in an oven at 120 °C and then calcining at 400 °C. For the added LSO, the additive-free LSO was stirred in pure water in which a 42% tetrafluoroboric acid aqueous solution was added 10 wt.% to the additive-free LSO powder, and dried in an oven at 90 °C. Two types of prepared powders weighing 0.3 g were pelletized to a size of about 1 mm thick with a diameter of 10 mm by a uniaxial press of 10 MPa and an isostatic pressure of 100 MPa and sintered in a furnace. For the sintered bodies, sintered densities were measured, crystal phases were confirmed by X-ray diffraction (XRD), surface structures were observed by a scanning electron microscope (SEM), and the ionic conductivities were measured by an impedance analyzer.As a result, dense sintered bodies with a relative density exceeding 90 % were achieved by holding the pellet of additive-free LSO at 1700 °C and the added LSO at 1450 °C for 10 hours. From the XRD, it was confirmed that each sintered body consisted of LSO single-phase. The sintered body of the additive-free LSO exhibited high peak intensities associated with (100), which means the c-axis of LSO is oriented in the in-plane direction. SEM observation revealed that the sintered body of additive-free LSO is composed of many columnar grains grown in the in-plane direction. On the other hand, the sintered body of added LSO exhibited an equiaxed-grained structure. Further, by measuring the ionic conductivity of each sintered body in the in-plane and out-of-plane directions, it is revealed that the ionic conductivity of the additive-free LSO showed a higher ionic conductivity in the in-plane direction than in the out-of-plane direction, while the added LSO showed lower ionic conductivity regardless of along in-plane / out-of-plane directions.These results indicate that the difficult-to-sinter properties of LSOs is not only due to the low diffusivity of La and Si, as previously reported, but also preferential grain growth in the c-axis direction impinging on and blocking each other to lower shrinkage speed. Although the sintering temperature could be lowered by enhancing equiaxial grain growth by adding tetrafluoroboric acid, the ionic conductivity became lower, which is probably due to too many grains with a, b-axis orientation of poor ionic conductivity and grain boundaries between them. It could have better prospect to support high ionic conductivity and low sintering temperature at the same time that exploiting the preferential grain growth characteristics of LSO in the c-axis direction. Figure 1

Exploration of Low-Temperature Formation Pathways for Garnet-Type Lithium-Ion Conductors

[Purpose] High-temperature sintering is necessary to obtain good contact between the cathode active material and the solid electrolyte in the development of all solid-state batteries. However, high temperature sintering causes the formation of a high resistivity layer, thus reduction of the sintering temperature is desirable. In this study, we investigated a low-temperature synthesis method in garnet-type lithium-ion conductors to synthesize fine particles without crystal growth that exhibit high sinterability at low temperatures. We explored a new reaction pathway to obtain garnet-type lithium-ion conductors at low temperatures by promoting spontaneous reactions between transition metal oxides at low temperatures through the refinement and amorphization of the raw materials.[Experimental] Li6.5La3Zr1.5Nb0.5O12(LLZNO) was synthesized by solid phase method using LiOH.H2O, ZrO2.La(OH)3, and amorphous Nb2O5 as precursors. The precursors were synthesized as follows: 1) nano-ZrO2 was synthesized by hydrolysis and coprecipitated with La(OH)3 to form a composite; 2) amorphous Nb2O5 was synthesized by DMF reduction.1 These starting materials were wet ball-milled, then pelletized and sintered at a predetermined temperature for 12 hours under an Ar atmosphere. The products were identified by powder X-ray diffraction. Changes in the local structure and electronic state of the transition metals at different sintering temperatures were analyzed by XAFS measurements.[Results & Discussions] Formation of an amorphous intermediate with high reaction activity was observed at 300 ºC by using Amorphous Nb2O5 to enhance the reaction activity of the starting material. The XAFS results show this amorphous intermediate has a disordered structure with a similar coordination environment around Nb to the La3NbO7 crystal phase. The ZrO2 synthesized by hydrolysis is a low-crystalline nanoparticle, and the coordination environment of Zr changes at 100 ºC lower than that of the commercial raw material. The formation of the target cubic LLZNO was confirmed at 400 ºC. The LLZNO crystalline phase formed from this amorphous intermediate is fine and could reduce grain boundary resistance in the preparation of sintered bodies. Finally, a single phase of LLZNO was obtained at 700 ºC, about 300 °C lower than the conventional solid phase method2. In summary, the results show that the destabilization of starting materials are effective for enhancing the reaction of transition metal oxides at low temperatures. These results suggest that controlling the phase stability of starting materials is an important parameter for the design of low-temperature synthesis of cubic LLZNO.[References]1: H. Iguichi et al., ACS Appl. Nano Mater., 5, 7658-7663, 20222: N. C. Rosero-Navorro et. al, Solid state Ionics, 285, 2016, (6-12)

Properties of Li1.3Al0.7Ti1.3(PO4)3 Ceramic Solid Electrolyte Densified by Cold Sintering Process

Replacing a flammable organic liquid electrolyte with a non-flammable solid electrolyte is the most promising way to improve the safety of Li-ion batteries. Oxide-based solid electrolytes have the advantages of good chemical stability and ease of handling, but for many of them, the high temperature sintering is required for densification and reduction of grain-boundary resistance for Li-ion conduction. However, co-sintering with electrode active materials at high temperature for fabrication of solid state batteries may cause side reactions and increase the internal resistance.1 Cold sintering (CS) is an attractive process for lowering the densification temperature of various ceramic materials.2 - 7 In this study, we applied CS for the densification of Li-ion conductive Li1.3Al0.7Ti1.3(PO4)3 (LATP) ceramic electrolyte. LATP powder was mixed with proper amount of deionized water or LiOH solution with various concentration as a transient liquid phase (TLP) and densified by CS at 200-250 °C for 0.5 h under uni-axial pressure of 600 MPa. After CS, the relative density of LATP pellet was increased to 85-90 %, and LiOH addition to TLP is effective for increasing the density. Grain size of LATP in the pellet is 0.5-1 µm and nanoparticle precipitation was observed near the grain-boundary area. Similar microstructure is confirmed in previous works.2 - 7 XRD measurements reveal the formation of LiTiOPO4 phase after CS. The amount of LiTiOPO4 phase tends to increase with LiOH concentration. It is thought that this heterogeneous phase precipitate during CS process and plays a role in bonding between LATP particles.From impedance measurement, we obtained ionic conductivity of 4 × 10-5 S/cm at room temperature in LATP densified at 250 °C by CS with TLP with an optimum LiOH concentration, which is higher than LATP densified by CS with TLP without LiOH (1.7 × 10-5 S/cm) and pressed LATP powder without adding TLP (3.6 × 10-7 S/cm). However, the conductivity of LATP by CS is lower than LATP sintered at 1000 ºC (= 2.3 × 10-4 S/cm). To improve ionic conducting property further, controlling the amount of precipitation phases after CS is necessary.This work was supported by Grant-in-Aid for Scientific Research (JSPS KAKENHI) Grant Number 22K18793 from the Japan Society for the promotion of Science (JSPS), and Innovative Elemental Technology Research in Green Technologies for Excellence (GteX) Program Grant Number JPMJGX23S7 of the Japan Science and Technology Agency (JST).References P. Jiang et al., Energy Technol. 11, 2201288 (2023).J. Guo et al., Angew. Chem., Int. Ed. 55, 11457-11461 (2016).J-H. Seo et al., Ceram. Internat. 43, 15370-15374 (2017).J-H. Seo et al., Jpn. J. Appl. Phys. 60, 037001 (2021).N. Hamao et al., Materials 14, 4737 (2021).N. Hamao et al., Chem. Lett. 50, 1784-1786 (2021).A. Mormeneo-Segarra et al., Ceram. Internat. 49, 36497-36506 (2023).

Electrochemical Properties of Garnet-Type Ta and Ga Co-Doped Li7La3Zr2O12 for Solid-State Li Batteries

Li-stuffed garnet-type oxide Li7La3Zr2O12 (LLZ) has attracted much attention because of the high ionic conductivity at room temperature, excellent thermal performance, and good chemical stability against Li metal.1,2 However, poor interfacial connection causes non-uniform Li plating and intergranular penetration of Li dendrite in polycrystalline LLZ when the cell is cycled particularly at high current densities, resulting in internal short-circuit failure.3,4 The tolerance for Li dendrite growth into LLZ is influenced by many factors such as the interfacial resistance between LLZ and Li anode, cell stacking pressure and microstructure (density and grain size) of LLZ. In this study, we fabricated Ga and Ta co-doped LLZ (Li6.55-3xGaxLa3Zr1.55Ta0.45O12, LGLZT) ceramic electrolyte and investigated the effects on the Ga amounts on the microstructure, ionic conductivity, and the tolerance for Li dendrite growth.LGLZT with Ga amounts x = 0.025, 0.05 and 0.10 were synthesized via a conventional solid-state reaction process. Sintering condition was set to 1150 °C for 2 hours in air. Relative densities for all sintered samples were ranged from 93-95 %. From XRD analysis, each sintered sample has a cubic garnet phase and diffraction peaks from other phases were not detected. Calculated lattice parameter was decreased with increasing Ga amounts x, due to the Ga3+ incorporation in the crystal lattice. In SEM observation, microstructure of sintered LGLZT was strongly influenced by x, because the amounts of liquid Li-Ga-O phase formed during high temperature sintering is also changed by x.5,6 When x increases, grain growth in sintered LGLZT is promoted and the segregation for Ga and O elements becomes more remarkable. Ionic conductivity of LGLZT at room temperature also enhanced with x, and maximum value of 0.84 mS/cm, which is much superior to the value for the sample without Ga (= 0.64 mS/cm). The effect of Ga amounts in LGLZT on the tolerance for Li dendrite growth will be discussed in the presentation.This work was supported by Grant-in-Aid for Scientific Research (JSPS KAKENHI) Grant Number 22H01468 from the Japan Society for the promotion of Science (JSPS).References R. Murugan et al., Angew. Chem., Int. Ed. 46, 7778−7781 (2007).A.J. Samson et al., Energy Environ. Sci. 12, 2957−2975 (2019).R. Inada et al., Batteries 4, 26 (2018).Y. Matsuki et al., J. Electrochem. Soc. 166, A5470−A5473 (2019)Y. Matsuda et al., Solid State Ionics 311, 69−74 (2017).Y. Yamazaki et al., Batteries 8, 158 (2022).

Engineered Porous Transport Electrode for Proton Exchange Membrane Water Electrolysers

Proton Exchange Membrane Water Electrolysers (PEMWEs) is among the most promising approaches for green hydrogen production due to its rapid response times and high-power density operation, which make this electrolysis technology well-suited to harvest the intermittent power from wind and solar plants. Nevertheless, the commercial breakthrough of PEMWE technology continues to face barriers due to its costs [1]. The porous transport layer (PTL) is one of the PEMWE components that facilitates the transport of incoming water to the catalyst layer and the removal of the product gases, hence it is very important for good electrolyser performance. The state-of-the-art PTLs are manufactured by high temperature sintering of titanium fibers or powders, which can generate oxidized surfaces that will reduce PEMWE performance. Furthermore, titanium is listed by the European Union as a critical raw material since 2020 [2], so it is advisable to reduce the amounts of its use to produce PTLs. Additionally, the (micro)structure of state-of-the-art PTLs is not optimized for efficient liquid and gas transport in electrolysis. The manufacturing process plays a key role in achieving PTLs with optimized liquid and gas transport as well as reducing the usage of titanium.In this work, we used lithography to manufacture PTLs in which the (micro-)structure can be optimized and the usage of titanium metal can be significantly reduced. The lithography manufactured PTLs were used as substrates to produce catalyst-coated electrodes (CCE) with (ultra-)low loadings of iridium and the PEMWE performance was evaluated, respect to CCEs manufactured on commercial PTLs. We demonstrate similar performance of the CCEs manufactured with the engineered PTL, with the advantage of using less titanium and being able to tune the (micro-)structure of the component.

A Novel Process to Achieve Enhanced Mechanical and Electrical Properties of (Mn,Co)3O4-Based Electrical Contact Layer for Solid Oxide Cells

To reduce ohmic losses and increase power output in an SOFC stack, electrical contact materials have been employed between the interconnect and oxide cathode. One of the possible candidate materials for the electrical contact layer is (Mn, Co)3O4, which is also used as the interconnect coating in an SOFC stack, due largely to its coefficient of thermal expansion that matches with the interconnect and cathode [1, 2]. The (Mn, Co)3O4 is electrically conducting, yet its conductivity remains several orders of magnitude lower than certain perovskite counterparts, such as (La, Sr)CoO3. In addition, (Mn, Co)3O4 often requires high sintering temperature (≥ 1000°C) when the oxide powders are used as starting materials [1, 3]. There is a need to develop novel processes to reduce the sintering temperature of (Mn, Co)3O4 to about 850°C, at which the sealing glass is sintered. In this work, we employ a new approach to fabricate (Mn, Co)3O4 spinels as the electrical contact materials. This innovation significantly enhanced the conductance of the contact layer and its bonding strength. The bonding strength with interconnect is evaluated by evaluating the maximum shear stress when the spinel layer is sandwiched by two 430 stainless steel coupons. Electrical resistance is measured for the contact layer with different Mn-Co ratios.

Resolving the Impact of Sr and Ni Diffusion on Moderate-Temperature Sintered BaZr0.44Ce0.36Y0.2O3/SrZr0.4Ce0.4Y0.1O3–NiO Half-Cells Interface for PCEC/PCFC

Proton-conducting solid oxide electrolytes are poised to play a transformative role in steam electrolysis (PCEC) and fuel cells (PCFC) application at moderate to low temperatures, given their high ionic conductivity and inherent advantages in the gas flow configuration over traditional solid oxide cells. However, their refractory nature necessitates high sintering temperatures to ensure sufficient densification which also compromises the protonic conductivity of the material. This paper investigates the impact of Sr and Ni segregation at the electrode/electrolyte interface in BaZr0.44Ce0.36Y0.2O3 (BZCY(54)8/92) proton conductinghalf-cells using a combination of high-resolution STEM-EDX, 3-dimensional atom probe tomography (APT), and Raman spectroscopy to understand structural modifications of the half-cells upon sintering at varying temperatures. Our half-cells are fabricated using an industrially established inverse tape-casting route with NiO-SrZr0.5Ce0.4Y0.1O3-δ as the substrate, ensuring minimal warping and no cracks in the end-fired state. After co-sintering at 1300 °C for 5 hours, the tri-layered green tapes achieved dense, gas-tight electrolyte layers with a He leakage rate well within the threshold necessary for cell operation (~5 × 10–5 hPa dm3 (s cm2)–1). Using Ba0.5La0.5CoO3−δ as the air electrode demonstrates remarkable capabilities and endurance within the 450-600°C temperature range, achieving a peak power density of 1.13 W cm-2 at 600 °C in the fuel cell mode and a high current density of 1.5 A cm-2 at 1.3 V in the electrolysis mode. Furthermore, It is apparent from the latter techniques that upon sintering above 1350 °C, the electrolyte material undergoes evident structural changes with new crystal defects that affect the perovskite host. Ni diffuses into the electrolyte layer and gets dissolved in the bulk while some segregate at the grain boundary, below monolayer coverage in either case (GNi 2.0 at%/nm2).Acknowledgment: The authors gratefully acknowledge financial support through JSPS KAKENHI Grant-in-Aid for Scientific Research (C), No. 19K05672, NEDO (International collaboration) JPNP20005, JSPS Core-to-Core (Solid Oxide Interfaces for Faster Ion Transport) and WPI-I2CNER sponsored by the World Premier International Research Center Initiative (WPI), MEXT, Japan.