Sintering Aid Research Articles

Effect of lead sintering aid to TiO2 photoanode for flexible dye sensitized solar cell

The commercial application of flexible dye sensitized solar cells (DSSCs) is somewhat limited due to the devices’ low conversion efficiency. The low sintering temperature in preparing the photoanode has caused poor interparticle contact, low charge transfer and low efficiency. Hence, this research aims to improve the interparticle contact of titanium dioxide (TiO2) photoanode with the novel use of lead (Pb) nanoparticles as sintering aid at low temperature. TiO2-Pb composite photoanode was prepared with different composition of Pb including 4% and 7% sintered at low temperature of 250°C. The research discovered that TiO2 photoanode mixed with 4% Pb composition showed the lowest charge transfer resistance (RCT) even at low sintering temperature. The RCT value was even lower than a commercial TiO2 photoanode sample that was sintered at 450°C. The addition of Pb sintering aid has improved interparticle contact in the photoanode via the neck formation at the TiO2-Pb interface and enhanced charge transfer despite the low temperature. The prepared photoanode samples displayed potential in developing highly efficient flexible DSSC.

Incorporation of Bi sintering aid to TiO2 photoanode for low temperature dye sensitized solar cell

The low conversion efficiency for low temperature dye sensitized solar cells (DSSCs) due to poor interparticle contact and charge transfer of TiO2 photoanode has been an issue for the solar cell. Therefore, the research aims to combat the issue with the implementation of bismuth (Bi) nanoparticles as sintering aid to the TiO2 photoanode. The addition of Bi sintering aid was found to form necks at the TiO2-Bi matrix seen in the morphological studies, despite the low sintering temperature of 200°C, due to the low melting point of Bi (271.4°C). The formation of these necks improved the interparticle contact and charge transfer of the photoanode that was observed in the electron transfer studies. Photoanodes with Bi sintering aid yielded lower charge transfer resistance (RCT) and series resistance (RS) than bare TiO2 photoanode by 15%-31%. The RCT and RS of TiO2-4%Bi photoanode (RCT=7.244 kΩ/cm2, RS=14.64 kΩ/cm2) was even almost comparable to the commercially prepared TiO2 photoanode at high temperature of 450°C (RCT=5.125 kΩ/cm2, RS=10.34 kΩ/cm2). Thus, indicating the potential for this approach in enhancing the overall performance of flexible low temperature DSSC in the future.

Microstructure and properties of silicon nitride ceramics fabricated by vat photopolymerization in combination with pressureless sintering

Silicon nitride (Si3N4) ceramics have been successfully manufactured using vat photopolymerization (VPP) technology. The formulated photocurable paste achieved a high solid loading (48 vol%) while maintaining low viscosity (3.2 Pa s at a shear rate of 30 s−1). Si3N4 ceramics doped with Al2O3–Y2O3 sintering aids were prepared using pressureless sintering at different temperatures (1650 °C, 1700 °C and 1750 °C) for 2 h. The resultant material exhibited a flexural strength of 613.3 ± 53.1 MPa, Vickers hardness of 12.6 ± 0.4 GPa, and a fracture toughness of 7.5 ± 0.3 MPa m1/2. X-ray diffraction (XRD) analysis has demonstrated a complete transformation from α-Si3N4 to β-Si3N4 at a sintering temperature of 1750 °C, where the resultant ceramic exhibited distinctive grain growth anisotropy. By investigating the shrinkage at different sintering temperatures, the sample at 1750 °C has a larger shrinkage in the Z-direction, which is also related to its anisotropic grain growth. Scanning electron microscopy (SEM) images have revealed the presence of elongated grains at a sintering temperature of 1750 °C. The combined effect of elongated grains and growth anisotropy serves to significantly enhance the overall mechanical properties of the material. This study advances current research on the preparation of high-performance Si3N4 ceramics by combining VPP technology with pressureless sintering.

Effects of Bi2O3–CuO additives on microstructure and microwave properties of low-temperature-sintered NiCuZn ferrite ceramics

In this study, (Ni0.2Cu0.2Zn0.6O)1.03(Fe2O3)0.97 ferrite ceramics with low microwave loss were synthesized through low-temperature sintering and doped with low eutectic mixture Bi2O3–CuO. Additionally, the influence of Bi2O3–CuO doping amount on phase composition, microstructure, and microwave performance of NiCuZn ferrite ceramics was systematically explored. It was found that all samples exhibited pure spinel phase. Moreover, scanning electron microscopy analysis revealed that appropriate doping amount of the Bi2O3–CuO mixture promoted grain growth and densification, leading to dense dual microstructure in NiCuZn ferrite ceramics. Notably, this microstructure significantly enhanced microwave properties of the material. For Bi2O3–CuO doping amount of 0.5 wt % and at sintering temperature of 910 °C, the NiCuZn ferrite ceramics exhibited low ferromagnetic resonance linewidth (ΔH ≈ 90 Oe), minimal dielectric loss (tanδε ≈ 2.73 × 10−4) at 9.3 GHz, and high saturation magnetization (4πMs ≈ 3644 Gauss). These results highlight the potential of Bi2O3–CuO as promising sintering aid, which could support the application of NiCuZn ferrite ceramics to microwave devices.

Ultra-low temperature co-sintering of water glass (WG)-bonded silicon carbide ceramic membranes for oil-water separation

Silicon carbide (SiC) ceramic membranes with high water permeance and good antifouling properties are promising for efficient oil-water separation. However, the high production cost of SiC membranes, in particular contributed by their high sintering temperatures, restricts the commercialization and full-scale applications of the membranes. In this work, a new coupling method of low-temperature co-sintering and spraying was proposed to prepare asymmetric water glass (WG)-bonded SiC microfiltration membranes for oil-water separation and reduce the cost of production. For this purpose, alkaline WG was used as the sintering aid to lower the sintering temperature to 600 °C and as the pH regulator to optimize the dispersion of the SiC powder. A facile optimization of the ultra-low temperature co-sintering program facilitated the formation of a crack-free multilayer of the membranes, by preventing thermal stress imbalance between the membrane layer and the support layer. The mean pore size of the co-sintered ceramic membrane was 0.25 μm, corresponding to high pure water permeance of above 2400 L· m−2·h−1·bar−1. In comparison with other reported ceramic membranes, the as-prepared co-sintered membranes exhibited higher stable-permeance (234.8 ± 9.4 L·m−2·h−1·bar−1) and a higher oil rejection (98.9 ± 0.2%) even under a lower transmembrane pressure (0.2 bar), which were attributed to the superhydrophilicity and underwater superoleophobicity of the membranes, during filtration with oil-in-water emulsions (500 mg· L−1). The low-temperature co-sintering method, aided by WG-based bonding, provides technical support for designing high performance ceramic membranes at reduced cost of production, which may promote their practical applications in wastewater treatment.

Towards sustainable electrochemistry: green synthesis and sintering aid modulations in the development of BaZr0.87Y0.1M0.03O3−δ (M = Mn, Co, and Fe) IT-SOFC electrolytes

In this study, BaZr0.87Y0.1M0.03O3−δ perovskite electrolytes with sintering aids (M = Mn, Co, and Fe) were synthesized by a sustainable approach using spinach powder as a chelating agent and then compared with chemically synthesized BaZr0.87Y0.1M0.03O3−δ (M = Mn, Co, and Fe) electrolytes for intermediate temperature SOFCs. This is the first example of such a sustainable synthesis of perovskite materials with sintering aids. Structural analysis revealed the presence of a cubic perovskite structure in BaZr0.87Y0.1M0.03O3−δ (M = Mn, Co, and Fe) samples synthesized by both green and conventional chemical methods. No significant secondary phases were observed in the samples synthesized by a sustainable approach. The observed phenomena of plane shift were because of the disparities between ionic radii of the dopants, impurities, and host materials. The surface morphology analysis revealed a denser microstructure for the electrolytes synthesized via green routes due to metallic impurities in the organic chelating agent. The absence of significant impurities was also observed by compositional analysis, while functional groups were identified through Fourier-transform infrared spectroscopy. Conductivity measurements showed that BaZr0.87Y0.1M0.03O3−δ (M = Mn, Co, and Fe) electrolytes synthesized by oxalic acid have higher conductivities compared to BaZr0.87Y0.1M0.03O3−δ (M = Mn, Co, and Fe) electrolytes synthesized by the green approach. The button cells employing BaZr0.87Y0.1Co0.03O3−δ electrolytes synthesized by the chemical and green routes achieved peak power densities 344 and 271 mW·cm−2 respectively, suggesting that the novel green route can be applied to synthesize SOFC perovskite materials with minimal environmental impact and without significantly compromising cell performance.

Effect of sintering aid combined vacuum infiltration on the properties of Al2O3-based ceramics via binder jetting

Binder Jetting (BJ) technology enables cost-effective and efficient fabrication of complex Al2O3-based ceramic components. However, in the process of manufacturing Al2O3-based ceramics using BJ, issues such as high sintering temperatures and relatively low sintered strength and relative density are encountered. In this study, we investigated the MnO2 sintering aid in combination with TiO2 sol-gel vacuum infiltration to introduce a MnO-TiO2-Al2O3 ternary sintering system, which could reduce the sintering temperature and enhance the strength and relative density of Al2O3-based ceramics. Through single-factor and response surface experiments, the effects of MnO2 addition, green body sintering temperature, infiltration time, and infiltration vacuum level on the properties and reinforcement mechanism of BJ Al2O3-based ceramics were studied. The research results revealed that with 10% MnO2 addition, a sintering temperature of 1450 °C, infiltration time of 60 s, and infiltration vacuum level of 24 KPa, the bending strength and sintered relative density of Al2O3-based ceramics reached 113.79 MPa and 78.13%, respectively. The bending strength was 48 times higher than that of the Al2O3 ceramic samples without sintering aid composite infiltration treatment, and the sintered relative density was improved by 41.85%.

Comparison between Lithium Substitution and Doping on the Physical and Piezoelectric Properties of Lead-Free BCZT Ceramics

Defects generation in ceramics by element substitution or doping may improve their properties. However, different results will be obtained even though the same element is involved due to different mechanisms. Ceramics Ba0.85Ca0.15Ti0.9Zr0.1O3 (BCZT) is one of the potential candidates to replace lead-based material PZT. However, the conventional method requires high-temperature calcination and sintering process to synthesize this material. Thus, Lithium (Li) can act as the sintering aid to lower the temperature at the same time, the properties of piezoelectric can be enhanced. In this paper, the structural, physical, and piezoelectric performance of lead-free Ba0.85Ca0.15Ti0.9Zr0.1O3 (BCZT) ceramics with Lithium Li substitution and doping, synthesized by the solid-state reaction method were studied. The substitution of Li increases the density, ρ and piezoelectric coefficient, d33 of BCZT which are 4.075 g/cm3 and 304.6 pC/N, respectively. These results demonstrate that Li substitution is more beneficial to the piezoelectric properties than doping because it produces higher grain boundary resistance and activation energy and has lower conductivity than doping. This can provide a definite strategy during the chemical composition design and manufacture of BCZT ceramics.

The Sintering Aids Maintain Giant Strain in Lead‐Free NBT–ST Piezoceramics Sintered at 975 °C

The 0.74Na1/2Bi1/2TiO3–0.26SrTiO3 codoped with Li2CO3 and B2O3 is studied to develop the low‐temperature sintered lead‐free piezoceramic for multilayer applications. The studied piezoceramics are synthesized by a conventional solid‐state reaction method. Their crystal structures, microstructures, ferroelectrics, and strain properties are analyzed. Interestingly, the addition of Li2CO3 and B2O3 reduces the sintering temperature of the 0.74Na1/2Bi1/2TiO3–0.26SrTiO3 sample from 1175 to 975 °C. All samples show a pseudocubic perovskite structure with a dense microstructure and an inhomogeneous grain size distribution. The electric‐field‐induced polarization loops of the samples are saturated at 4 kV mm−1. More importantly, the 0.74Na1/2Bi1/2TiO3–0.26SrTiO3 + 1 wt%Li2CO3 + 1 wt%B2O3 sample sintered at 975 °C shows a Smax/Emax value of 510 pm/V under an applied electric field of 2 kV mm−1, which is promising for multilayer lead‐free piezoelectric actuator applications.

Composite phase change material based on Al alloy with durability of over 10,000 cycles for high-temperature heat utilization

High-temperature latent heat storage (LHS) technology using alloy-based phase change materials (PCMs) is promising for high-temperature heat applications owing to its high heat storage capacity at a constant temperature. Microencapsulated PCMs (MEPCMs) coated with stable ceramics can help prevent corrosive reactions observed in alloy PCMs during heat storage. Because MEPCMs are considered as ceramic particles, a composite PCM can be prepared by compositing them with a sintering aid. In this study, composite PCMs consisting of MEPCM with Al–12 mass% Si alloy (melting point: 577 °C) particles with diameters of 31.7 or 68.2 μm, and α-Al2O3 as the sintering aid were prepared. The MEPCM used in the preparation of the composite PCM included alumina hydroxide and various alumina polymorphs as coatings. Pellet-like compacts were successfully produced by mixing each MEPCM with α-Al2O3. After heat treatment, the composite PCMs retained their shape. In particular, the latent heat capacities of the composite PCMs made from small and large MEPCMs with α-Al2O3 coatings were 171 and 231 J g−1, respectively. Moreover, the composite PCMs retained their shape and more than 80 % of their latent heat capacity after 10,000 and 1000 cycles. The developed composite PCMs, with their high latent heat capacity and durability, can be employed for high-temperature heat applications.

One-step sintering process for high-performance SiC membranes for efficient filtration of dust-laden gas

Silicon carbide (SiC) ceramic membranes are known for their remarkable attributes, including resistance to acid and alkali corrosion, exceptional tolerance to thermal shock, and high mechanical strength. These properties have garnered considerable attention for dust-laden gas filtration. However, large-scale applications of SiC membranes are limited because of the high sintering energy consumption in membrane formation. In this study, a preparation method for high-performance and low-cost SiC membranes using a co-sintering process was proposed. In this method, SiC particles with a 100-μm average particle size were uniformly mixed with sintering aids and SiC green supports were prepared via a dry pressing process. Subsequently, SiC dispersion was coated on the SiC green supports via a spray coating method to prepare membrane layer. Through optimization of the sintering process and sintering atmosphere, the sintering stress difference during co-sintering was released. Finally, a defect-free membrane surface was fabricated. The carbon powder in the green supports was utilized as a pore-forming agent and to prevent small particles in the SiC membrane layers from infiltrating the SiC green supports, decreasing the mass transfer resistance in the application process. The SiC ceramic membrane had a mean pore size and a gas permeance of 3.90 μm and 246.33 m3 m−2 h−1. In addition, when subjected to identical average pore size and porosity conditions, it exhibited a high Darcy's permeability coefficient, indicating favorable structural characteristics for the membrane. Additionally, the membrane was optimized to have a 99.9 % rejection of solid particles in dusty gases, including nanometer (0.3 μm) and micron (2.5 μm) solid particles. This study has introduced a preparation method for low-cost and high-performance SiC membranes for industrial dust-laden gas filtration.

High-entropy design in sintering aids for proton-conducting electrolytes of solid oxide fuel cells

Sintering aids are commonly used to improve the sinterability of proton-conducting oxides, whereas the sintering aid elements are being used alone in previous research. In this study, a high-entropy design method for the BaCe0.4Zr0.4Y0.2O3 (BCZY) proton-conducting oxides sintering aid is proposed. In contrast to the use of sintering aids such as Ni, Fe, Cu, Co, and Zn alone, the high-entropy design allows for the simultaneous use of all five elements, resulting in the new composition BaCe0.4Zr0.4Y0.15Ni0.01Cu0.01Co0.01Fe0.01Zn0.01O3 (HE-BCZY). Compared to conventional BaCe0.4Zr0.4Y0.15M0.05O3 (BCZYM, M = Ni, Cu, Co, Fe, Zn) materials, the sinterability of the new HE-BCZY material is significantly greater than that of BCZYM, despite the fact that the concentration of sintering aids is the same. Following sintering at 1300 °C, the HE-BCZY electrolyte membrane is completely dense. In addition, the HE-BCZY electrolyte has a higher conductivity than BCZYM. The low sintering temperature allows the successful preparation of proton ceramic fuel cells (PCFCs) with the HE-BCZY electrolyte, and the fuel cell reaches a high peak power density of 1218 mW cm−2 at 700 °C, which is much higher than that of PCFCs using BCZY-based electrolytes. In addition, the excellent chemical stability of HE-BCZY is maintained under both H2O and CO2 conditions. Consequently, a fuel cell employing the HE-BCZY electrolyte operates without detectable degradation for 200 h. This study demonstrates that although the high-entropy design is seldom used for sintering aids of proton-conducting oxides, it is an intriguing and promising strategy for creating high-performance electrolyte materials with good sinterability, high conductivity, and excellent stability.

Sinterability of sodium bismuth titanate-based electroceramics at low temperatures

The demand for robust multilayer ceramic capacitors with high-temperature and high-power capabilities is surging. Cost-effective production is a key challenge, often linked to precious metal electrodes like Pt, Pd, and Ag in multilayer ceramic capacitors (MLCCs). To address this, cost-efficient base metal electrodes such as Cu and Ni are sought. Promising lead-free options are Na0.5Bi0.5TiO3 (NBT)-based materials. However, their sintering temperatures exceed Cu's melting point (1085 °C), necessitating sintering aids for compatibility. We investigated several low-temperature sintering aids (Li2O, Na2O, Bi2O3, B2O3, ZnO, and V2O5) to lower the sintering temperature of Na0.5Bi0.5TiO3-BaTiO3-CaZrO3-BiAlO3 solid solutions. Results reveal NBT-based materials' sensitivity to acceptor dopant incorporation from sintering aids, impacting electrical properties. Yet, we successfully reduced the sintering temperature to 975 °C, suitable for Cu co-sintering, with minimal adverse effects on capacitor properties using well-tuned sintering aids.

Effect of sintering temperature and time on the microstructure, density, phase, selected mechanical and tribological properties of [formula omitted] composite fabricated by the spark plasma sintering

The purpose of this study is to examine the effect of different temperatures and sintering times on the microstructure, density, hardness, bending strength, coefficient of friction (COF), fracture toughness, and abrasion rate of Cf/Si3N4 fabricated via the spark plasma sintering (SPS) technique. For this target, the α phase of Si3N4 powder was prepared alongside sintering aids and carbon fiber. Next, five samples were sintered via SPS method at temperatures 1750 °C, 1800 °C, and 1850 °C, under the pressure of 70 MPa, and times of 10, 15, and 20 min. The obtained data illustrated that with an elevation of the sintering temperature from 1750 °C to 1850 °C, the density of the sintered body increased from 91.11 % to 93.03 %, and the hardness rose from 536 to 916 Vickers. Furthermore, upon prolonging the holding time from 10 min to 20 min, the density was enhanced from 93.03 % to 96.53 %, and hardness improved from 916 to 1433 Vickers. The results showed that with an elevation of temperature and time of sintering, the abrasion rate dropped from 14.4 × 10-7 to 4.4 × 10-7 g/N.m due to reducing the porosity of the sample. Finally, with a temperature rise from 1750 °C to 1850 °C, the bending strength of the samples decreased.

Lower-temperature sintered high energy density fine-grained sodium bismuth titanate - strontium bismuth titanate ceramics multilayer capacitors

The breakdown field strongly determines the energy density of energy-storage ceramic capacitors. In this work, a compound sintering aid of CuO and SiO2 was preferably selected to explore the effect on sintering behavior and energy storage of sodium bismuth titanate - strontium bismuth titanate (NBT-SBT) relaxor ferroelectrics. The optimum sintering temperature promotes a dense microstructure and fined-grain size in NBT-SBT, which contributes to an increase in breakdown strength. Meanwhile, the appropriate CuO/SiO2 ratio retains the advantages of the high polarization value of NBT-SBT. Specifically, when sintered at 1040 °C with 0.2 wt% SiO2 and 0.8 wt% CuO composite sintering aids, the NBT-SBT bulk ceramics achieved an energy storage density of 4.09 J/cm3 under a high electric field of 270 kV/cm. Owing to the lower sintering temperature, the NBT-SBT achieved co-firing with 30/70 Ag/Pd electrodes. Finally, multilayer ceramic capacitors with a recoverable energy density of 8.43 J/cm3 have been successfully fabricated.

NaBr-Assisted Sintering of Na3Zr2Si2PO12 Ceramic Electrolyte Stabilizes a Rechargeable Solid-state Sodium Metal Battery.

Solid-state metal batteries with nonflammable solid-state electrolytes are regarded as the next generation of energy storage technology on account of their high safety and energy density. However, as for most solid electrolytes, low room temperature ionic conductivity and interfacial issues hinder their practical application. In this work, Na super ionic conductor (NASICON)-type Na3Zr2Si2PO12 (NZSP) electrolytes with improved ionic conductivity are synthesized by the NaBr-assisted sintering method. The effects of the NaBr sintering aid on the crystalline phase, microstructure, densification degree, and electrical performance as well as the electrochemical performances of the NZSP ceramic electrolyte are investigated in detail. Specifically, the NZSP-7%NaBr-1150 ceramic electrolyte has an ionic conductivity of 1.2 × 10-3 S cm-1 (at 25 °C) together with an activation energy of 0.28 eV. A low interfacial resistance of 35 Ω cm2 is achieved with the Na/NZSP-7%NaBr-1150 interface. Furthermore, the Na/NZSP-7%NaBr-1150/Na3V2(PO4)3 battery manifests excellent cycling stability with a capacity retention of 98% after 400 cycles at 1 C and 25 °C.

Influence of CuO addition on the sintering temperature and giant dielectric properties of (In0.5Nb0.5)0.05Ti0.95O2 ceramics

Co-doped TiO2 ceramics exhibit great potential as high-performance giant dielectric materials. However, their excessively high sintering temperature renders them unsuitable for economical industrial production. The giant permittivity of these ceramics is closely correlated with the concentration of Ti3+ ions present. Adding a sintering aid to the ceramics is an effective method to reduce the sintering temperature. CuO, a common sintering aid, not only reduces the sintering temperature but also potentially enhances the Ti3+ ions concentration through the multivalence of Cu element, further optimizing their giant dielectric properties. Therefore, the effects of CuO addition on the sintering condition, microstructure, and dielectric properties of In and Nb co-doped TiO2 ceramics were investigated. The results indicate that CuO effectively lowers the sintering temperature of the ceramics. However, the presence of a large number of Cu+ ions inhibits the formation of Ti3+ ions, resulting in the disappearance of their giant dielectric properties. Upon annealing at 1150 °C for 2 h in air, the Ti3+ ions concentration significantly increases in the ceramics, consequently restoring their giant dielectric properties. Additionally, a new dielectric relaxation appears around 100 kHz, likely arising from the conductivity difference between the shallow layers and cores of grains induced by annealing. Furthermore, annealing enhances the grain boundary resistance, thereby reducing the low-frequency dielectric loss of the ceramics.

Preparation of water–impermeable NASICON solid electrolyte separators for aqueous/nonaqueous hybrid sodium–ion cells using alumina as a sintering aid

The Na3Zr2(SiO4)2PO4 (NZSP)-based Na Super Ionic Conductor (NASICON) is widely known as a Na–ion conductive ceramic, and its stability in water makes it a promising solid electrolyte separator for aqueous and aqueous/nonaqueous hybrid Na–based cells. Some sintering additives have been used to enhance the densification of NASICON ceramics, while decreasing their stability against water because of their hygroscopicity. In this paper, we propose the use alumina (Al2O3) as a sintering aid for the preparation of dense NASICON ceramics. For this purpose, 5 mol.% of alumina powder was mixed with commercially available NZSP powder and the obtained composite green pellet was sintered at 1200 °C for 6 h in air. The crystal structure of the prepared NASICON ceramics, characterized via X–ray diffraction, significantly matched that of the pristine NZSP powder with a monoclinic (C2/c) structure. In the sintered sample, the boundaries of the NZSP particles were densified by a Na–Al–Si–P–based glass component. The sintered NASICON ceramic sample was used as a solid electrolyte separator in an aqueous/nonaqueous hybrid Na-ion cell. A hybrid cell constructed from a Na3LiTi5O12 negative electrode and 3 wt% H2O2-added 1.0 M Na2SO4 aqueous electrolyte/1.0 M sodium bis[(trifluoromethyl)sulfonyl]amide (NaTFSA)-based nonaqueous electrolyte exhibited a stable cell voltage of 2.4 V during several charge–discharge cycles. The Al2O3-added NZSP sintered ceramics can be used as solid electrolyte separators for aqueous/nonaqueous hybrid sodium-ion batteries.

Low-temperature co-fired PZNN-PZT multilayer piezoelectric ceramics with excellent electrical and bending properties

A 0.65 Pb(Zr0.47Ti0.53)O3–0.35[Pb(Zn0.1Ni0.9)1/3Nb2/3]O3 (PZNN-PZT) piezoceramic with sintering aids of Li2CO3, Bi2O3, CuO and Sm2O3 was prepared via a traditional solid reaction to achieve a high-performance multilayer actuator. The microstructure and electrical properties of ceramic bulks were systematically explored. The piezoceramics sintered at various temperatures show multi-phase co-existence. The sintering aids are beneficial for grain growth and microstructure densification. The piezoceramic sintered at 960 °C possesses relatively desirable electrical properties, including d33 ∼ 550 pC/N, kp ∼0.7 εr ∼2200, tan δ ∼0.021, Qm ∼71, Tc ∼240.5 °C, Pr ∼24.44 μC/cm2 and Ec ∼823.7 V/cm. Furthermore, we employed the tape casting and low-temperature co-fire methods to fabricate a PZT-PZNN/Ag–Pd multilayer piezoceramic of 7 × 7 × 36 mm3 in dimension with a single ceramic film of about 80 μm in thickness. The Ag–Pd electrode is effectively bonded with the ceramic layer, especially chemical binding induced by oxygen diffusion at some partial areas, which plays a crucial role in high binding strength (∼9.2 MPa). The multilayer piezoceramic exhibits outstanding actuating characteristics of high Smax ∼55.53 μm @ 150 V, and low H ∼19.8% @ 150 V together with outstanding stiffness of 70.87 N/μm @ 150 V.

Core-rim microstructure formation and mechanical properties of TiB2 ceramics with TiC, B4C, Co, and Mo sintering aids

This research investigates titanium diboride (TiB2) ceramics, renowned for their exceptional properties: high hardness, chemical inertness, and thermal stability. The challenge lies in achieving dense structures through pressureless sintering, given TiB2 ceramics' high melting point and low self-diffusion coefficient. To address this, a combined method of liquid phase and reactive sintering is employed, focusing on the influence of metallic cobalt (Co) and molybdenum (Mo) as sintering aids to enhance microstructural and mechanical properties. Vacuum sintering at 1900 °C facilitates the reaction between TiC and B4C, forming TiB2, with Co improving wettability and Mo inhibiting high-temperature grain growth. The matrix of 90TiB2+10(TiC + B4C + Co + Mo) recipe achieved 94.7 % relative density and a hardness of 31.97 GPa. Moreover, adding polyvinyl butyral (PVB) assists in creating gas evacuation channels during the sintering process. The research also reveals the reaction between TiC and B4C, forming (TiMoB)C with molybdenum, while the eutectic Co–Mo alloy dissolves into borides, promoting densification and forms dense core-rim structures.