Sintering Aid Research Articles

Transient liquid-phase assisted low-temperature spark plasma sintering of TiCN with Si aids

The feasibility of densifying TiCN at a much lower temperature than currently by using transient liquid-phase assisted spark plasma sintering (SPS) with Si aids is demonstrated. Firstly, it is shown that TiCN can be fully densified by SPS at 1400 °C with only 5 vol% Si aids, a temperature at which TiCN hardly densifies at all, resulting in novel superhard (∼21.5 GPa) ceramic composites having fine-grained (<1 µm) multi-particulate microstructures with TiCN as the main phase and SiC, TiSi2, and TiN as secondary phases. It is found that all this is because Si is a reactive sintering aid (2TiC0.5N0.5+3Si→SiC+TiSi2+TiN) and because during SPS two eutectic melts are formed, first a Si-rich one at ∼1275 °C and then a TiSi2-rich one at ∼1375 °C. Secondly, it is shown that TiCN can also be fully densified by SPS at only 1275 °C with 5 vol% Si aids, giving the same superhard ceramic composites as at 1400 °C, but requiring much longer holding because only the Si-rich eutectic melt is formed. And thirdly, it is shown that the densification of TiCN+Si is more favoured with increasing vol% Si aids, which is important for its pressureless sintering, and also that these superhard multi-particulate TiCN-based composites are slightly less hard but slightly tougher and lighter the more SiC, TiSi2, and TiN secondary phases are formed in situ during SPS by the reaction between TiCN and Si.

Sintering Behavior, Microstructure and Microwave Dielectric Properties of Li2TiO3-Based Solid Solution Ceramics with Lithium Fluoride Addition for Low-Temperature Co-Fired Ceramic Applications

Nowadays, low-temperature co-fired ceramic (LTCC) technology has become one of the main forms of manufacturing electronic devices. However, a majority of microwave dielectric ceramics are not suitable as LTCC materials due to their high sintering temperatures. Developing novel LTCC materials with good microwave dielectric properties is extremely urgent. In this paper, an LiF sintering aid was added to Li2Ti0.8(Co1/3Nb2/3)0.2O3 (LTCN) ceramics to explore new LTCC materials. The sintering behavior, microstructure and microwave dielectric properties of LTCN + x wt% LiF ceramics were investigated in detail. The results indicated that the addition of LiF increased the degree of disorder in the LTCN matrix, transforming it from a monoclinic to a cubic crystal system. The ceramics exhibited relatively dense and homogeneous microstructures at the sintering temperature of 950 °C as the LiF doping amount was not less than 2 wt%. By LiF doping, the quality factor (Q × f) value was significantly enhanced due to the improved microstructure. Meanwhile, the temperature coefficient of resonant frequency (τf) of LTCN ceramics was successfully regulated to the near zero value owing to the negative τf characteristic of LiF. Excellent microwave dielectric properties of dielectric constant (εr) = 19.01, Q × f = 144,890 GHz, τf = −1.52 ppm/°C were obtained when the sample doped 3 wt% LiF was sintered at 950 °C for 3 h. Furthermore, the good chemical compatibility of the LTCN-3 wt% LiF ceramic with silver electrodes suggested that the ceramic was a potential material for LTCC applications.

Properties comparison of pure Al2O3 and doped Al2O3 ceramic cores fabricated by binder jetting additive manufacturing

Binder jetting additive manufacturing (BJAM) was widely used for fabricating complex ceramic cores due to its low cost and convenient process. In this study, the effects of layer thicknesses (50–100 μm) and sintering temperatures (1300–1400 °C) on the properties of pure Al2O3 and 95 wt% Al2O3–4 wt.% TiO2–1 wt.% CuO ceramics (doped Al2O3 ceramics) were investigated, respectively. For the green parts with a layer thickness of 50 μm, the maximum density, porosity, and bending strength values of doped Al2O3 ceramic increase by 14.9%, 6.3%, and 39.6% when compared with those of pure Al2O3 ceramic. When the green parts were sintered from 1300 °C to 1400 °C, the optimal values of doped Al2O3 ceramic with a layer thickness of 50 μm were 2.377 ± 0.036 g/cm3, 39.34 ± 1.20%, and 27.44 ± 1.29 MPa, respectively, and the increase rates were 23.0%, 27.2%, and 86.8% compared with those of pure Al2O3 ceramic. The dimensional shrinkage of each axis gradually increased with the increase of the layer thicknesses and sintering temperatures, and the Z-axis was always larger than X-axis and Y-axis. When the sintered part was 50 μm and 1300 °C, the minimum values of pure Al2O3 ceramic were 2.00 ± 0.15%, 1.86 ± 0.15%, and 1.59 ± 0.15%, and those of doped Al2O3 ceramic were 13.57 ± 0.20%, 12.46 ± 0.57%, and 12.60 ± 0.17%, respectively. Additionally, when the sintered part was 100 μm and 1400 °C, the maximum values of pure Al2O3 ceramic increase to 4.90 ± 0.20%, 3.94 ± 0.13%, and 3.61 ± 0.25%, and those of doped Al2O3 ceramic were 18.81 ± 0.19%, 17.27 ± 0.75%, and 16.77 ± 0.39%, respectively. These results indicate that adding sintering aids can promote low-temperature sintering and improve the mechanical strength of ceramic cores.

Effect of CeO2-Y2O3 sintering aids on the microstructure and properties of corundum-based composite ceramics

ABSTRACT Reducing the preparation cost of alumina ceramics has received significant attention, as alumina is one of the most widely used structural ceramics. In this study, corundum-based composite ceramics with a white corundum-to-zircon powder mass ratio of 7:3 were selected as the matrix. CeO2 and Y2O3 doped corundum-based composite ceramics were prepared via pressureless sintering. The total content of CeO2-Y2O3 was set at 10 wt% to study the effects of different temperatures and CeO2-Y2O3 ratios on the properties of the corundum-based composite ceramics. Physical phase and microstructural analyses of the corundum-based composite ceramics were performed using X-ray diffraction and scanning electron microscopy, respectively. The results showed that the sintering temperature of the corundum-based composite ceramics could be effectively reduced by using a solid solution of CeO2 and Y2O3. The best sintering temperature was 1400°C, and the best composition was 5 wt% CeO2-5 wt% Y2O3. The physical properties of the corundum-based composite ceramics prepared under these technological conditions include a flexural strength of 386.2 MPa, hardness of 13.5 GPa, density of 3.9128 g/cm3, linear shrinkage of 16.31% and an apparent porosity of 0.62%.

Low-firing of CaAl2B2O7 ceramics with Li2O–B2O3–SiO2 and LiF additions

Lithium borosilicate (LBS) and lithium fluoride (LiF) are verified to be effective sintering aids for CaAl2B2O7 microwave dielectric ceramic to reduce the sintering temperature and lower the activation energies. Benefiting from the liquid phase sintering, low-firing, low permittivity and low-loss CaAl2B2O7 microwave dielectric composite has been successfully obtained. Typically, CaAl2B2O7 assembled with 1 wt % LBS composite possesses desirable properties of εr = 5.91, Q × f = 39,443 GHz, τf = −23.51 ppm/°C (@16.53 GHz). For composite ceramics with 0.5 wt % LiF, the optimal microwave dielectric properties are εr = 6.08, Q × f = 37,295 GHz, τf = −22.39 ppm/°C (@15.78 GHz). The two kinds of composite are densified at 875 °C, with co-existed CaB2O4 and liquid phase. The mechanism underlying the low temperature sintering is revealed by well-matched wettability and lower activation energy of composite ceramics with additions.

Particle size modulation for effectively optimizing the dielectric and mechanical properties of La2O3–B2O3 based glass-ceramic/ceramic LTCC substrates

Lanthanum borate-based glass-ceramic has recently received considerable attention in the field of high-frequency communications as a sintering aid, due to the low sintering temperature and the precipitation of crystalline phases with excellent dielectric and mechanical properties. Importantly, the densification and crystallization behaviors of glass-ceramic are not only determined by its composition, but also affected by various processing parameters, such as the initial particle size, which is rarely explored for optimizing the dielectric and mechanical properties of lanthanum borate-based glass-ceramic/ceramic composites. Herein, La2O3–B2O3–CaO–P2O5–SiO2 (LBCPS) glass-ceramics with a series of initial particle sizes are achieved by ball milling method through controlling the milling time. Employing LBCPS glass-ceramics with different particle sizes as the sintering aid, various LBCPS/Al2O3 composites are fabricated, and the dielectric and mechanical properties of which are further investigated. Notably, the LBCPS/Al2O3 composite with a moderate glass-ceramic particle size of 2.7 μm exhibits the excellent comprehensive performance with a low dielectric loss of 8.6 × 10−4 at 9.8 GHz and a high flexural strength of 199 MPa. Moreover, the influencing mechanisms of the glass-ceramic particle size on the crystallization, microstructure, and densification of the LBCPS/Al2O3 composite have also been systematically explored and proposed. This research work provides an intriguing strategy for optimizing the dielectric and mechanical properties of the glass-ceramic/ceramic as the high-performance low-temperature co-fired ceramic (LTCC) substrate.

Enhanced properties of Li0.42Zn0.27Ti0.11Mn0.1Fe2.1O4 ferrites co-fired with Bi2O3–B2O3 additive at low sintering temperatures

In this study, Li0.42Zn0.27Ti0.11Mn0.1Fe2.1O4 ferrites were co-fired with Bi2O3–B2O3 (BB) additive at low sintering temperatures (∼920 °C), and the effects of BB additive on various properties of Li–Zn ferrites were systematically investigated. First of all, the existence of BB additive would not pollute the spinel phases of Li–Zn ferrites, in contrast, it could make the ferrites well-ripened at low temperatures. The micro-morphology results revealed that the introduction of BB additive could significantly promote the grain growth, where the average diameter of grain size increased from 0.81 μm (0.0 wt % BB) to 8.12 μm (0.5 wt % BB), leading to a higher densification degree and density. Owing to the liquid phase formed in the sintering process, magnetic properties of the Li–Zn ferrites were improved with the assistance of BB additive. The saturation flux density (Bs) and saturation magnetization could reach a maximum value of 319.3 mT and 74.2 emu/g, respectively. The coercivity (Hc) and ferromagnetic resonance (FMR) linewidths (ΔH) could reach a minimum value of 176.3 A/m and 243.2 Oe, respectively. Finally, it is noted that the optimal values of these parameters are obtained under the condition of 0.5 wt % BB additive doped, and most magnetic properties would be deteriorated when exceeding the above content. Thus, BB additive is considered as a promising sintering aid for synthesizing Li–Zn ferrites at low temperatures, which will play a vital role in the development of low-temperature co-fired ceramics (LTCC) technology.

Low temperature sintering, structure and electrical properties of BiFeO3-BaTiO3 based piezoelectric ceramics using CuO-B2O3 composite sintering aids

Piezoelectric ceramics usually have high sintering temperature, which cannot meet the low-temperature co-firing requirements of ceramics and metal electrodes in production of micro devices. Here, we studied the effects of CuO-B2O3 binary composite sintering aids on the sintering behavior, phase composition, microstructure, and electrical properties of the bismuth ferrite-barium titanate (0.7BiFeO3-0.3BaTiO3, BFO-BT) based lead-free piezoelectric ceramics. We found that the CuO-B2O3 sintering aids can effectively lower the sintering temperature of the BFO-BT ceramics to 880 ℃, which is far below the melting point of metal electrodes. The BFO-BT based ceramics with 0.5 wt% sintering aids exhibited excellent dielectric, ferroelectric, and piezoelectric properties (εm = 83029, Pm = 38.4 μC/cm2, Pr = 33.8 μC/cm2, d33 = 119 pC/N) with high Curie temperature (TC = 460 ℃). Meanwhile, this ceramic possessed high depolarization temperature (Td) near 300 ℃, demonstrating a good temperature stability of piezoelectricity. This study provides a feasible solution to improve the compatibility of lead-free piezoelectric materials and low-melting point metal electrodes for fabrication of micro piezoelectric devices.

Zirconium Carbide for Hypersonic Applications, Opportunities and Challenges.

At ultra-high temperatures, resilient, durable, stable material choices are limited. While Carbon/Carbon (C/C) composites (carbon fibers and carbon matrix phases) are currently the materials of choice, zirconium carbide (ZrC) provides an option in hypersonic environments and specifically in wing leading edge (WLE) applications. ZrC also offers an ultra-high melting point (3825 K), robust mechanical properties, better thermal conductivity, and potentially better chemical stability and oxidation resistance than C/C composites. In this review, we discuss the mechanisms behind ZrC mechanical, thermal, and chemical properties and evaluate: (a) mechanical properties: flexure strength, fracture toughness, and elastic modulus; (b) thermal properties: coefficient of thermal expansion (CTE), thermal conductivity, and melting temperature; (c) chemical properties: thermodynamic stability and reaction kinetics of oxidation. For WLE applications, ZrC physical properties require further improvements. We note that materials or processing solutions to increase its relative density through sintering aids can have deleterious effects on oxidation resistance. Therefore, improvements of key ZrC properties for WLE applications must not compromise other functional properties. We suggest that C/C-ZrC composites offer an engineering solution to reduce density (weight) for aerospace applications, improve fracture toughness and the mechanical response, while addressing chemical stability and stoichiometric concerns. Recommendations for future work are also given.

Ultra-high quality factor of transparent Al2O3 ceramics fabricated by vacuum sintering and post hot isostatic pressing

Transparent polycrystalline Al2O3 (PCA) ceramics were prepared by vacuum sintering followed by hot isostatic pressing (HIP) using MgO as a sintering aid. The prepared sample with thickness of 0.8 mm exhibits a transmittance of 50% (λ = 640 nm) and 78% (λ = 4.5 μm) in the entire visible band and infrared band, respectively. Effects of additive content, sintering temperature as well as HIP method on the microstructure of Al2O3 ceramics were systematically investigated. The experimental results show that the effect of HIP on the transmittance of PCA in the visible light region is particularly obvious, which can increase the transmittance by almost two times. In particular, the quality factor of pure Al2O3 ceramics prepared by the same process is as high as 1,120,970 GHz (at 13.6 GHz) owing to extremely high density and reduction of the grain boundary, which render Al2O3 ceramics potential candidates for fabrication of multilayer electronic devices.

Ultrafast high-temperature sintering (UHS) of ZrB2-based materials

ZrB2 is one of the most promising materials for extreme environment applications, especially in the aerospace field, due to the combination of superior thermophysical properties and low density. Nevertheless, pure ZrB2 is intrinsically hard to sinter, requiring either the application of intense external pressure or the use of sintering aids. In the present work, the feasibility of ultrafast high-temperature sintering (UHS) for the densification of commercial ZrB2 was explored. Thanks to the addition of B4C as a sintering aid, Densities up to 92–98% could be obtained in just 2 min. Hardness of 16.3–17.8 GPa was obtained for the UHS ZrB2-based ceramics, similar to what is reported in the literature using slower, more sophisticated and energy-consuming sintering approaches like spark plasma sintering. These first results show that UHS could provide a quick and simple way to produce high-performance ZrB2-based components with just a few minutes of processing time in pressure-less conditions.

Competition of Li+ and Cu2+ ions dopant in BiAlO3–Pb(Zr,Ti)O3 piezoelectric ceramics in low temperature sintering processes

Sintering with sintering aids is widely used to achieve a low sintering temperature of lead-based piezoelectric ceramics. In this study, two low-temperature sintering aids, namely Li2CO3 and CuO, were doped into the x BiAlO3-(1-x) PZT + 0.2 wt% MnO2 composition, and the microstructures and electrical properties were investigated for these ceramics prepared via solid-phase reaction method. Differential Scanning Calorimetry (DSC) indicated that the Li2CO3 liquid phase formed at a lower temperature than that of CuO, while co-dopant of Li2CO3 and CuO will result in a competition between Li+ and Cu2+ ions during the low-temperature sintering processes, which negatively impacts piezoelectric properties. The results demonstrated that the piezoelectric properties of ceramics with only Li2CO3 or CuO additives are much better than ceramics with co-doped Li2CO3 and CuO additives. Ceramics with 0.3 wt% Li2CO3 or 0.1 wt% CuO sintering aid were sintered at 1000 °C, resulting in excellent piezoelectric coefficients (d33) exceeding 300 pC/N and mechanical quality factors (Qm) of 500 were obtained, respectively. This work provides inspiration for low-temperature sintering strategies in other ceramic materials.

Improved densification in cold sintering of gadolinia‐doped ceria with reactive sintering aids

AbstractThis study explores a novel reactive cold sintering method for improving the density of gadolinia‐doped ceria (GDC) ceramics while reducing the annealing temperature. Instead of using deionized water as an aid in conventional cold sintering, stoichiometrically mixed Ce(NO3)3·6H2O and Gd(NO3)3·6H2O precursors were added as additives during the CSP in this study. The effects of processing parameters such as sintering temperature and additive content on the relative density of the compacts were investigated using synthesized GDC and commercial GDC powders as raw materials. The results showed that with the aid of precursors, GDC ceramics were sintered up to 90% of their theoretical densities at 850°C and up to 94% at 950°C when the synthesized nanopowder GDC was used. Additionally, the sintering mechanism was investigated, and it was found that the GDC generated by the precursor reaction effectively filled the gaps between the original particles, promoting densification of the sample after cold‐pressing.

Preparation, characterization and application of BaZr0.1Ce0.7Y0.2O3-δ for a high-performance and stable proton ceramic electrochemical cell

The high sintering temperature (＞1500 °C) of the electrolyte is the main challenge for the application of proton ceramic electrochemical cells (PCECs). In this work, we prepare BaZr0.1Ce0.7Y0.2O3-δ (BZCY) electrolyte materials by various synthetic routes, compare their physicochemical properties and optimize their applications in PCEC. The BZCYs powder prepared by the solid state reaction method shows a large grain size of 2–3 μm and is used in the support layer. The optimal proportion of the support is determined according to the thermal expansion characterization. The BZCYp powder from the ultrasonic-assisted co-precipitation method presents well dispersed particles of 30∼50 nm and is used as the electrolyte layer and in the fuel electrode layer. The electrolyte becomes very dense after co-sintering with the support at 1400 °C without any sintering aids, giving a low conducting activation energy of 0.26 eV. The single cell demonstrates excellent performance and good stability. Under steam electrolysis mode, the cell gives 840 and 260 mAcm−2 @1.3V at 600 °C and 500 °C. Under cell mode, the cell displays 0.46 and 0.21Wcm−2@0.7V at 600 °C and 500 °C, respectively.

Phase Composition and Physicomechanical Properties of β-Sialons Prepared Using NaF as a Sintering Aid

Phase Composition and Physicomechanical Properties of β-Sialons Prepared Using NaF as a Sintering Aid

In operando characterization of the ionic conductivity dependence on liquid transient phase and microstructure of cold-sintered Bi2O3-doped Li1.3Al0.3Ti1.7(PO4)3 solid-state electrolyte

A disruptive sintering technique, Cold Sintering Process (CSP), has been used to produce cold-sintered samples of Bi2O3-doped Li1.3Al0.3Ti1.7(PO4)3 (LATP) as solid-state electrolyte (SSE). An in operando impedance study has been performed to shed light on this sintering process. In this work, Bi2O3 and 3 m acetic acid solution sintering aids were synergistically added to LATP powders to sinter at low temperature. Effects of Transient Liquid Phase (TLP) content on the sintering behavior, phase composition, microstructure, and electrochemical properties were all investigated for a LATP doped with 2 wt% Bi2O3 (optimal content) solid-state electrolyte (SSE). The data revealed that the final electrical properties, which are the key parameter decisive for their application, are defined by the following sintering parameters: Transient Liquid Phase (TLP) content, temperature, pressure, and dwell time. Using acetic acid 3 m as TLP, LATP-based samples can be cold-sintered at optimized sintering conditions of 150 °C and 700 MPa of uniaxial pressure for 90 min. The resultant SSE shows a high ionic conductivity (4.5·10−5 S cm−1) at room temperature (RT) and relative density (∼95%), which demonstrates the effectiveness of the low-temperature sintering process by optimizing the ionic conductivity of LATP-based SSE, also reducing preparation costs and CO2 emissions.

Liquid phase sintering of yttrium oxide: The effect of Al2O3 and SiO2 additives

Solid-state sintering of Y2O3 is difficult and requires high-temperature heat treatment or the use of a sintering additive. In this study, liquid-phase sintering was utilized to produce dense Y2O3 bodies with fine-grained microstructure. Al2O3 and SiO2 were added to a commercial nano-Y2O3 powder using aluminum nitrate and tetraethylorthosilicate (TEOS) as the precursors; the samples were uniaxially pressed at 100 MPa and sintered at 1500 °C and 1650 °C. The addition of the sintering aids increased the relative density of the samples sintered at lower temperatures; also, the sintering aids suppressed grain growth. The dissolution of Y2O3 into the liquid phase changes the solid-liquid interfacial energy resulting in the formation of isolated yttrium-silicate/yttrium-aluminate grains and accounts for the suppression of the growth of yttria grains.

Effect of Mo-Doping on the Proton-Conducting BaCe0.9-xMoxY0.1O3-δ Electrolyte at Intermediate Temperature SOFCs

Perovskites have been attracting much attention because of their many potential applications as solid electrolytes in solid oxide fuel cells (SOFC). Among various kinds of perovskite materials, the Y2+ doped BaCe0.9Y0.1O3-δ (BCY) have been investigated extensively. It is noted that the doped BCY have good stability and relatively high protonic conductivity. However, the sintering temperature of BCY is very high above 1600 °C to achieve the required densification. High sintering temperature leads to evaporation of barium and the subsequent segregation of doped elements. As a result of this, the electrochemical properties of BaCe0.7Zr0.1Y0.2O3-δ electrolyte are reduced. At high temperatures, it’s difficult to maintain the porous structure of electrodes and causes the formation of impurity phases. So, in order to overcome this issue, we doped Mo- to BCY and reduce the sintering temperature of the electrolyte without comprising its performance. The sol-gel method was followed for the preparation of Ba1Ce0.9-xMoxY0.1O3-δ (BCMY, x=0.025%-0.2%) powder. The precursor's Ba(NO3)2, Ce(NO3)3.6H2O, Y(NO3)3.6H2O, and (NH4)6Mo7O24.4H2O in the stoichiometric ratio were dissolved in a mixture of water, citric acid, and glycine used as chelating agents in the molar ratio of 1:2:1. The solution was heated at 100 °C and was constantly stirred till it becomes a gel. The dried precursor was then heated at 350 °C for 2 hrs to remove the organic residues through combustion. Afterward, it was calcined at a temperature of 1100 °C for 10 hrs and finally, a white powder of BCMY was obtained. The synthesized BCMY electrolytes were sintered at 900, 1000, and 1100 °C to observe the effects of low sintering temperature on the structural, morphological, and electrical properties of BCMY. All BCMY electrolyte materials exhibited a crystalline perovskite structure and were found to be thermally stable as shown in XRD (Fig. 1 (a, b)). The morphology and element distribution of the BCY and BCMY electrolyte were observed by the scanning electron microscope (SEM, (Fig. 1c)) and energy-dispersive x-ray spectroscopy (EDX). SEM images show that BaCe0.9Y0.1O3-δ electrolyte sinterability and densifications are significantly improved. Fully dense pellets are sintered by using 0.025-0.2 mole% Mo. Energy dispersive spectroscopy shows that sintering aids are uniformly distributed throughout the structure. This study demonstrates BCMY as a dense proton-conducting electrolyte for intermediate-temperature solid oxide fuel cells. The BCMY with Mo-doping appears to be a potential candidate for sintering at low temperatures. Sintering facilitates addition from oxygen vaccines, which ease ionic conduction through the electrolyte, result in a low activation energy of at moderate temperatures. Fully dense pellets are sintered by using 0.025-0.2 mole% Mo. This method of decreasing the BCMY sintering temperature is useful in improving the SOFC performance.

Development of Large Area Protonic Ceramic Cells for Stack Implementation

Protonic Ceramic fuel and electrolysis Cells (PCCs) offer a promising alternative to oxide-conducting cells in the fields of renewable energy and hydrogen. Due to their operation at reduced temperatures and with pure hydrogen flows (while in SOCs the hydrogen flow is diluted with water) they present a potential of cost reduction in large-scale applications. However, the SOC technology is more advanced and is already commercialized at the stack level and implemented in demonstration plants. The newer PCC technology is not yet at the same level as cells and stacks are not commercially available, but research on the scale-up and implementation of cells into stacks and systems is a major topic in the PCC landscape. A major obstacle to the increase of the PCC technology readiness is the scale of the cells themselves. Research on electrochemical activity is mostly reserved for button cells with areas of less than 10 cm2. For the cells to be integrated into a stack, the active area needs to be larger to allow for a cost-efficient production of larger-scale devices. However, the manufacture of large cells is complicated by the increase in frequency of defects such as pinholes, cracks, bends among others. These prevent the use of a cell in or decrease the quality of an electrochemical performance measurement. Therefore, a careful and thorough adaption of the manufacturing process is necessary. Compared to common laboratory-scale preparations such as powder pressing, the use of wet chemical industrial processes allows for the elaboration of larger cells and the establishment of protocols that are more easily scalable and may be utilized in commercial applications in the future.Using a multi-step manufacturing wet chemical route, a number of hydrogen electrode-supported cells with areas of over 60 cm2 and half-cells with a maximum of 75 cm2 have been achieved. First, the hydrogen electrode is manufactured via tape-casting from a slurry containing NiO and BCZY721 (BaCe0.7Zr0.2Y0.1O3-d) as the functional materials. After drying, the cutouts are coated with a BCZY721 electrolyte ink by screen-printing. The two layers are co-sintered at 1300°C to yield a half-cell. The low sintering temperature limits the effect of shrinkage of the half-cell, while a dense electrolyte is nonetheless ensured by utilizing infiltrated ZnO as a sintering aid. The thusly produced half-cells are then coated with air electrode layers composed of LSCF (La0.4Sr0.6Co0.2Fe0.8O3-δ) or BGLC (Ba0.5Gd0.8La0.7Co2O6-δ) compositions. To improve the thermomechanical compatibility, a composite layer of BCZY271 and the respective air electrode material is applied before the pure air electrode layer. A second sintering step is performed to ensure a good bonding at the interface between the electrolyte and the air electrode layers. The resulting microstructure is a dense electrolyte of 5-10 µm thickness, whereas the electrodes remain highly porous to ease the gas diffusion. The significant parameters crucial to a high yield of suitable large cells are the electrolyte ink composition and screen-printing process parameters, and the sintering configuration (temperature and pressure applied). The effects of these parameters on the cell output and the electrochemical characterization results of the manufactured complete cells including electrochemical impedance spectroscopy (EIS) will be discussed. As a step towards the implementation into stacks, results on these cells in a serial repeating unit (SRU), i.e. including interconnects and sealing, will also be discussed. Figure 1

(Digital Presentation) Prolonged Operation Strategies For Solid Oxide Fuel Cell Through Barrier Layer-Based Interface Engineering

As one of the current benchmark cathode materials, La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) is in the process of widely commercialization. Normally, a high-density barrier layer, such as doped Ceria (Gd0.1Ce0.9O2-δ, GDC), is essentially introduced in SOFC single cell between Zirconia electrolyte and cathode, in order to prevent chemical incompatibility and elements diffusion. However, in large-scale fabrication, the GDC barrier layer is typically screen-printed onto the as-sintered YSZ electrolyte. Consequently, the post-sintered GDC layer is often porous. Increase GDC barrier layer density can effectively facilitate oxygen ions transfer and inhibit elements diffusion. Therefore, in this study, four YSZ electrolyte supported symmetrical cathode cells with various barrier layers are investigated, i.e. (1) screen printed GDC (named as GDC), (2) screen printed GDC with Cobalt Nitrate sintering aid (GDC-Co), as well as hydrothermal modified cells named as (3) GDC-HY and (4) GDC-Co-HY, respectively. The results show largely decreased Rohm of ~20% when sintering aid are used in GDC barrier layer. Furthermore, both Rohm and Rp values are extremely stable after further hydrothermal modification, with growth rate of 0.014 and 0.03 Ω·cm2/kh for GDC-Co-HY, respectively, which are much lower than 0.22 and 0.248 Ω·cm2/kh for pristine GDC-Co. Current study suggests that increasing the GDC barrier layer density by hydrothermal modification is an effective method to enable better cell performance and more stable long-term operation.Figure 1 Evolution of (a) Rohm and (b) Rp with aging time in air. Microstructure of the GDC surfaces (c-f) and cell fractures (g-j). Figure 1