High Sintering Research Articles

Achievement of high photoluminescence quantum yield orange-red phosphors by designing Eu2+ reduction environment for multi applications

The high photoluminescence quantum yield (PLQY) orange-red phosphor, which is of great significance for the application of phosphor-converted light-emitting diode (LED). Herein, the novel BaSrLu4O8:Eu2+ orange-red phosphor was synthesized, and the PLQY is enhanced from 30 % to 91 % by Al2O3 assisted sintering. Combined with the trap energy level analysis, it is considered that the addition of Al2O3 introduces new vacancies, which release electrons during high temperature sintering, creating a more favorable environment for the reduction of Eu3+, increasing the Eu2+ luminescence center in the matrix and improving the PLQY. The white LED device prepared with BaSrLu4O8:Eu2+ and Y3(Al,Ga)5O12:Ce3+ has a color rendering index of 84.4 at a low correlated color temperature of 4295 K. Meanwhile, the luminous brightness of the orange LED prepared by BaSrLu4O8:Eu2+ can maintain 89 % of the original light intensity in the simulated foggy day illumination experiment, which proves its excellent lighting prospect as an automobile steering lamp in foggy and smog extreme conditions. The results indicate that this work provides a new strategy for the reduction of Eu2+ while realizing the multi-application of phosphors.

Regulating the resistivity of rare-earth nickelates electronic phase transition perovskites via NiO composition

Although rare-earth nickelates (ReNiO3) exhibit widely adjustable metal-to-insulator transition (MIT) properties, it is yet difficult to control their material resistivities to cater for potential applications in correlated electronics. Herein, we demonstrate a strategy to regulate the material resistivities of ReNiO3 while maintaining their relative abrupt MIT properties by compositing with the NiO nanoparticles and afterward high oxygen pressure sintering. Introducing the more insulating NiO as a secondary phase within ReNiO3 (e.g., NdNiO3 and SmNiO3) elevates their material resistivities across two orders of magnitudes while maintaining a similar critical temperature (TMIT) and its resultant resistive change at a moderate compositing ratio (e.g., <80 %). The nearest-neighbors-hopping (NNH) model and linear model were used to fit the low-temperature electric transportation properties for both the insulating and metallic phases of ReNiO3, and it indicates that the pristine carrier transportation modes can be well preserved despite a high compositing ratio of NiO up to 80 %. Similar effects cannot be achieved by using other more insulating compositing oxides, such as BaBiO3, LaAlO3, and NiFe2O4, as the abruption in resistive change across TMIT was not preserved at a similar high compositing ratio (e.g., >20 %), while their carrier transportation modes varied at much smaller composition ratio. It is worth noticing that the compositing with NiO also improves the mechanical strength of ReNiO3, and this benefits their practical applications in electronic devices.

Effect of Polybenzimidazole Coating on Acetylene Black for Durability of Polymer Electrolyte Membrane Fuel Cell

One of the difficulties to retain Pt interfacial structure during PEMFC operation is arose from the high activity and large surface energy of the Pt nanoparticle, which facilitate i) Ostwald ripening, where the Pt particle size increases by a dissolution-redeposition process upon redox cycling and ii) agglomeration of Pt nanoparticles by sintering. These phenomena lead to the loss of Pt interfacial area and deteriorate the PEMFC performance. In addition, stability of carbon supports used as an electron conductive Pt supporting material is also essential to improve Pt stability since carbon corrosion catalyzed by Pt also takes place at a high potential (mainly over 1.0 V), which triggers the detachment of Pt and subsequent agglomeration. Thus, the use of durable carbon supports against the oxidation is crucial to increase the PEMFC durability. Since it is known that sp2 carbons are more thermodynamically stable than sp3 carbons upon oxidation, the use of highly graphitized carbons such as carbon nanotubes (CNTs) have been investigated to employ and it is proved that the use of such carbons mitigates the Pt agglomeration and thus enhance the PEMFC durability. However, an absence of the anchoring sites for Pt deposition on such graphitized carbon surface such as -OH and -COOH connected on sp3 carbons make the uniform deposition of Pt nanoparticles rather difficult. And it is pointed out that the weak interaction between the graphitized carbon surface and Pt nanoparticles often induces the sintering of Pt particles and, therefore the improvement of the Pt‒carbon interfacial strength will further improve the Pt stability. Although, general strategy to introduce anchoring sites for the highly graphitized carbons is to oxidize the surface by harsh chemical or physical treatments, such oxidation always involved the introduction of the sp3 sites and resulted in the decrease of the durability of carbon supports. We have developed smart method to introduce anchoring sites without creating sp3 carbons on the highly graphitized carbon surface, where the carbons are coated by polymer having anchoring sites for metal ions. In this method, polymer such as polybenzimidazole (PBI) is coated on the pristine (non-oxidized) carbons and can act as the anchoring site for the Pt deposition. Therefore, Pt can be deposited onto the surface of highly graphitized carbon such as CNTs without oxidizing the CNTs. Indeed, we reported that PEMFC having PBI-coated CNT as a carbon support showed excellent durability upon fuel cell accelerated durability test (ADT) between 1.0 ‒ 1.5 V. In that research, oxidized-CNT was used as a comparison since direct Pt deposition onto the pristine CNT was rather difficult and, in addition, we used the ADT protocol designed to degrade the carbon (1.0 – 1.5 V). Thus, we successfully demonstrated the advantage of the PBI coating to preserve inherent carbon durability but the effect of the PBI coating for the Pt stability was not investigated. We also demonstrated that the PBI-coating on Vulcan could enhance the durability of Vulcan-based PEMFC. However, in that research, PBI coating improved Vulcan stability mainly because the coverage of micropore of Vulcan decelerated the oxidation of the carbon surface during the ADT between 1.0 ‒ 1.5 V. Therefore, the effect of PBI coating for the stability of Pt particles was not observed. In this study, to clarify the effect of PBI coating for Pt stability and PEMFC durability, ADT between 0.6 ‒ 1.0 V designed to study Pt stability was applied for the PEMFC having PBI-coated carbons as a carbon support. Here, Acetylene Black (AB) was chosen as the carbon support since 1) AB shows high electrochemical stability due to their high crystallinity and Pt sintering triggered by the carbon corrosion during the ADT can be avoided and 2) direct Pt deposition on AB was possible and no oxidation pretreatment is necessary for the reference samples. As the result, we found that MEA employing PBI-coated AB shows only 8% decrease in the maximum power density, while MEA containing non-coated AB shows 34% decrease after the ADT. Structural analysis of the electrocatalysts after the ADT reveals that the PBI anchors both Pt nanoparticle and ionomer upon ADT and maintains their interfacial structure. We conclude that the polymer-coating method is promising both for the improvement of the durability and the activity of the PEMFC.

Doped Nasicon-Type Solid Electrolytes for Sodium-Ion Batteries from Scalable Spray-Flame Synthesis

Due to the limited availability of raw materials, sodium-ion batteries (SiB) are a viable alternative to lithium-ion batteries. However, liquid-electrolyte-based SiBs have a comparably low energy density and suffer from safety issues similar to their lithium-ion-based counterparts. To address these issues, solid-state SiBs are a promising option and sodium super ionic conductors (NaSICON) are suitable solid electrolytes for such systems. They exhibit good mechanical properties and chemical stability, high ionic conductivity and compatibility with sodium metal based anodes enabling high energy density [1]. One of the best studied NaSICON materials is Na3Zr2Si2PO12 (NZSP) with a high ionic conductivity in the order of 10-4 –10-3 S·cm-1 at room temperature [2]. Conventional synthesis methods of this class of materials such as solid-state reaction and liquid-phase synthesis have several drawbacks due to time-consuming process steps such as milling, high temperature sintering, precipitation, washing and drying steps to obtain the final product.We present spray flame synthesis (SFS) as a new approach for the synthesis of nanosized NaSICON materials. Recent studies have shown that sintering of nanoparticular NZSP precursors offers several advantages: A high specific surface area, which increases the sintering activity, and short atomic diffusion paths, allowing high homogeneity and phase purity to be achieved at comparatively low sintering temperatures [3]. In SFS, metal salts dissolved in organic solvents are combusted resulting in fine metal oxide particles. They are characterized by transmission electron microscopy (TEM), X-Ray diffraction (XRD) and Raman-Spectroscopy for structural and morphological investigation. Elemental information is obtained via energy-dispersive X-Ray spectroscopy (EDX). Ionic conductivities of sintered NZSP pellets are measured by impedance spectroscopy.In our approach, nanoparticles with a median diameter of around 5–9 nm are obtained. The pristine particles consist of crystalline ZrO2, homogeneously covered with an amorphous layer consisting of the elements Na, Si, P and O. After a short annealing step for 1h at 1000°C, this mixture can be converted almost quantitatively into the desired rhombohedral NZSP phase. Moreover, aliovalent dopants were successfully added for the synthesis of Na3+2xAxZr2−xSi2PO12 with A = Mg or Ca. Pressed pellets sintered at 1100°C for 3h to a relative density of ~92% showed - for a material sintered for such a short period of time - a surprisingly high ionic conductivity of up to 7.9×10-4 S·cm-1 (Mg-doped).In conclusion, a novel approach for the preparation of NZSP allowing the phase formation at relatively low temperatures is demonstrated. Spray flame synthesis is an elegant and promising possibility for the scalable production of solid electrolytes, which also holds great potential, especially with regard to further improvement of ionic conductivity through targeted doping.[1] Zhang et al., ACS Appl. Energy Mater., 3 (2020) 7427; doi.org/10.1021/acsaem.0c00820[2] Narayanan et al., Solid State Ion., 331 (2019), 22; doi.org/10.1016/j.ssi.2018.12.003[3] Jalalian-Khakshour et al. J.Mater.Sci., 55, (2019) 2291; doi.org/10.1007/s10853-019-04162-8

Co-Sintering of Lithium Aluminum Germanium Phosphate (LAGP) Glass/Powder Composite Electrolyte for Multilayer Ceramic Batteries

Inorganic solid electrolytes are one of the key materials instead of organic liquid electrolytes for next-generation all-solid-state batteries (ASSBs). The advantages of ASSBs are long cycle life and high safety due to the non-flammable of the solid electrolyte. The ASSBs can be stacked layer by layer, reducing the volume in battery packaging and resulting in increased energy density. These ASSBs can be applied to wearable or healthcare or smart home devices in the form of multilayer ceramic battery (MLCB), in addition to energy storage devices and electric vehicles. However, the MLCBs are difficult to fabricate due to the high sintering temperature and high interfacial resistance of the solid electrolyte. The Li-based solid electrolytes of NASICON-type have received much attention as prospective solid electrolytes due to their high ionic conductivity and high stability against moisture. Especially, lithium aluminum germanium phosphate (LAGP) is potential solid electrolyte material in the NASICON family due to superior stability. LAGP glass electrolyte was selected to enable sintering at low temperatures and reduce resistance at the interface for the application to MLCB.In this study, a LAGP-based solid electrolyte ceramic sheet was prepared using glass/powder composite at 750 °C. The obtained LAGP-based solid electrolyte exhibited a NASICON-type hexagonal structure and a total ionic conductivity of 1.45 × 10-4 S/cm at 25 ˚C. A Coin cell with the LAGP composite electrolyte, LiCoO2 (LCO) as cathode, and Li metal as anode was assembled. The coin cell was charged and discharged by using a battery cycler and the charge capacity was approximately 130 mAh∙g-1. Additionally, we prepared a LiMnPO4 glass-based cathode (LMP) using conventional melt quenching techniques and then stacked it layer by layer with the LAGP electrolyte and co-sintered at 650°C. After co-sintering the LAGP/LMP cell, it was confirmed that the interface between the LAGP composite electrolyte and the LMP cathode was well attached, and its ionic conductivity maintained a value similar to that of the LAGP composite electrolyte. Subsequently, an electrochemical analysis of the LAGP/LMP cell was performed.

Modulation of Rh species in Rh/Al2O3/FeCrAl-foam structured catalysts for steam reforming of toluene

Steam reforming of tar is an appealing way for tar elimination during biomass gasification. In this work, structured Rh/Al2O3 supported on FeCrAl-foam catalysts with different Rh species contents (Rh0, RhiOx and Rh(AlO2)y) were modulated through calcination and/or reduction at different temperatures for toluene steam reforming. Among all the structured catalysts and conventional supported catalysts, the structured Rh/Al2O3/FeCrAl-foam catalyst, calcined in air at 300 °C followed by reduction with hydrogen at 600 °C, showed superior activity as well as excellent resistance to sintering and coke deposition. Such high performance can be attributed to the suitable Rh0/RhiOx ratio as well as the enhanced mass transfer capability. The integrated studies of controlled catalytic tests, catalyst characterizations, TPSR, H2O-TPD and in-situ DRIFTS revealed that metallic Rh0 site was responsible for the cleavage of the C-C/C-H bonds in toluene. The activate ability of H2O was governed by the Rh0/RhiOx ratio, while the RhiOx specie played a significant role, which further promotes the reaction activity and eliminate coke deposition. Furthermore, the RhiOx specie enable the catalyst with high sintering resistance, due to the strong affinity to the Al2O3 surface. However, the Rh(AlO2)y specie was inactive. The catalytic performance was controlled by balancing the toluene activation and H2O dissociation. Consequently, rational tuning of these species is crucial for obtaining high-performance Rh/Al2O3 catalysts for steam reforming of toluene.

Cold sintering of BaZr0.8Y0.2O3-ẟ ceramics: Phase formation and grain boundary properties

Electrochemical devices based on the proton conducting ceramic BaZrO3 have shown their immense potential for efficient energy conversion and gas separation processes at intermediate temperatures. A major drawback of this material class is the inevitably high sintering temperature, which is necessary to reach sufficient densities for gas tightness. Recently, cold sintering has been applied to densify BaZrO3 – BaCeO3 solid solutions at low temperatures using a partial dissolution of the Ce-rich phase. Here, we apply the method to BaZr0.8Y0.2O3-ẟ (BZY20), which is a Ce-free proton conducting ceramic. We show that densification by cold sintering is viable at temperatures between 150 °C and 250 °C under uniaxial pressures of 400 MPa and deionized water as a sintering aid. The dissolution of yttrium from BZY20 during cold sintering acts as the trigger for densification at low temperatures but forms Y(OH)3 as an instable side product. Therefore, we developed a two-step cold sintering process that adds an additional thermal treatment between 900 and 1100 °C directly after the cold sintering process to enable electrochemical characterization and transmission electron microscopy investigations.

Single crystal growth and physical properties of La, Co doped (Eu,Ca)FeAs2

We report the growth of La and Co doped (Eu,Ca)FeAs2 ((Eu0.5Ca0.4La0.1)(Fe0.97Co0.03)As2, La,Co-(Eu,Ca)112) single crystals via high temperature sintering method and their superconducting properties were investigated. Unlike other iron-based superconductors, single crystals of this compound were relatively easy to obtain by sintering at high temperatures from stoichiometric compositions. Using small amounts of precursor (0.5 g) and optimization of the isothermal temperature and temperature gradient profiles, relatively large (up to 2.8 mm2) 112 single crystals were obtained. X-ray diffraction measurements on the 112 single crystals indicated only (0 0 l) Bragg peaks. Energy dispersive X-ray spectroscopy analysis indicated the composition of the grown 112 single crystals to be (Eu0.54, Ca0.38, La0.09)(Fe0.96, Co0.037)As2. The coexistence of superconductivity and Eu2+ magnetism, as reported in EuFeAs2, was confirmed. The onset of superconducting transition temperature of 30 K (magnetic susceptibility) and 31.8 K (electrical resistivity) was observed in the La,Co-(Eu,Ca)112 single crystal grown by thermal gradient method. Our present results indicating further optimization of Co doping may enhance the superconductivity in these compounds. The La,Co-(Eu,Ca)112 iron-based superconductor, which have unique physical properties and are relatively easy to grow as single crystals, may bring an interesting playground in the field of superconducting materials.

Crystal structure of AlFe0.95.

Three B2-type inter-metallic AlFe1 - δ phases (0.18 < δ < 0.05) in the Al-Fe binary system were synthesized by smelting and high temperature sinter-ing methods. The exact crystal structure for δ = 0.05 was refined by single-crystal X-ray diffraction. The amount of vacancy defects at the Fe atom sites was obtained by refining the corresponding site occupancy factor, converging to the chemical formula AlFe0.95, with a structure identical to that of ideal AlFe models inferred from powder X-ray or neutron diffraction patterns.

Experimental study and performance improvement of recycled building bricks based on microwave sintering technology

The preparation of recycled building bricks (RBB) from construction spoil with microwave technology is a green, highly efficient, and energy-saving method. However, the low dielectric loss and high sintering temperature of construction spoil result in a long continuous heating time, which is not conducive to energy conservation or the lifespan of microwave equipment. This study proposes the use of hematite tailings as an auxiliary sintering material to enhance the response of RBB to microwave radiation. Orthogonal experiments were used to analyze the influence of the mass fraction of hematite tailings, the mass fraction fly ash, forming pressure and sintering temperature on the sintering efficiency, mechanical properties, and other basic properties of RBB. The optimum materials and process parameters for manufacturing RBB were obtained. These results indicated that hematite tailings can effectively improve the sintering efficiency of RBB under microwave radiation. The mass fraction of tailings is the most important factor affecting the sintering efficiency, and sintering efficiency increases with an increase in the tailings mass fraction. These four factors have a significant impact on the mechanical properties of RBB. Higher sintering temperature and forming pressure improve the compressive strength, which will decrease with the increasing mass fraction of tailings and fly ash. The average compressive strength of the samples in No. 9 group was the highest, reaching 34.44 MPa. The No. 9 group (30 wt% hematite tailings, 4 wt% fly ash, 66 wt% construction spoil, 20 MPa forming pressure and 800 °C sintering temperature) is considered the best material and process parameter combination for manufacturing RBB with microwave technology due to its highest strength, high solid waste content, good sintering efficiency and performance.

Ce:LuAG transparent ceramics for high-brightness solid-state lighting: Fabrication and effect of Ce concentration

Compared to phosphor and phosphor in glass, phosphor ceramics have higher thermal properties, and are less prone to thermal quenching. (Ce,Lu)3Al5O12 (Ce:LuAG) has better thermal stability than most of the phosphors, such as (Ce,Y)3Al5O12 (Ce:YAG). However, the high melting point of Lu3Al5O12 (LuAG; up to 2010 °C) presents a great challenge in producing transparent ceramics (TCs), so a series of Ce:LuAG nanopowders with high sintering activity were prepared by the co-precipitation method and then used as initial materials to obtain x at.% Ce:LuAG (x = 0.05, 0.1, 0.2, 0.3, 0.35, 0.4, 0.5, 0.55, 0.6, 0.65, 0.7) TCs by vacuum sintering at 1775 °C for 10 h. Moreover, the luminous properties of typical Ce-doped LuAG phosphors were systematically investigated using excitation by light-emitting diodes or laser diodes (LEDs/LDs). The emission intensity of 0.4 at.% Ce doped sample is the highest among all TCs with Ce amount ranging from 0.05 to 0.7 at.% at room temperature. The photoluminescence intensity of 0.4 at.% Ce:LuAG only decreases by 12.5% from 25 to 225 °C. The 0.4 at.% Ce:LuAG based on 0.8 W LEDs and 1.1 W LDs has the optimum luminous flux of 71.5 and 113.7 lm and the luminous efficiency of 89.3 and 101.4 lm∙W−1, respectively. As Ce concentration increases, a decrease in the luminescence saturation threshold of TCs is observed with a blue laser power density of 2.5–36.9 W∙mm−2. A high-flux yellow-green light of 1166.9 lm is obtained from 0.1 at.% Ce:LuAG when excited with a high-power LD with an energy density of 36.9 W∙mm−2. This work explored the best Ce doping level in Ce:LuAG TCs, as well as the luminescence saturation threshold in remote laser lighting applications.

Design, synthesis and improved sintering behavior of core-shell Mo–Cu composite powders

Molybdenum-copper composites have attracted increasing attention due to their excellent properties in terms of electrical conductivity, thermal conductivity and mechanical property, which are closely related to the density and composition of the sintered material. However, high temperatures are required to obtain high sintering density, resulting in loss of copper in most cases. In this work, a novel core-shell Mo–Cu composite powder was prepared by a ball-milling method followed by hydrogen reduction. The phase compositions and microstructure of prepared powders were studied by XRD, TEM and EDS, and the formation process of core-shell structure of Mo–Cu powders was discussed in detail. It was shown that the significant difference in reduction temperatures between molybdenum and copper oxides contributes to the formation of core-shell structure.

Microstructure, mechanical properties and arc erosion behavior of CuW composites prepared by high energy ball milling and spark plasma sintering

In this study, the CuW75 composites with excellent interfacial bonding were successfully fabricated by the combination of high energy ball milling and spark plasma sintering (SPS). The microstructure, comprehensive properties, and arc erosion resistance of CuW75 composites were investigated. The results show that with the increase of milling time, a layered structure is gradually formed in the mixed powder of CuW75 composites, and the grain size remains basically unchanged after 40 h. When the ball milling time is 40 h, the CuW75 composites exhibits excellent comprehensive properties, with an electrical conductivity of 24.39% IACS, a hardness of 441 HB, and a relative density of 98.1%. The compressive strength of CuW75 composites after ball milling for 40 h is 49.7% higher than that of commercial CuW75 composites. In terms of arc erosion resistance, the CuW75 composites after ball milling for 40 h have a shallower surface and larger ablation areas. The reason is that good interface bonding and grain refinement improve the strength of the matrix and makes the arc move rapidly along the grain boundaries, retarding downward erosion.

Ionic Conductivity of Electrolytes Composed of Oleate-Capped Yttria-Stabilized Zirconia Nanoparticles.

Yttria-stabilized zirconia (YSZ) is a highly promising electrolyte material for solid oxide fuel cells (SOFCs). We investigated the conductivity-enhancing effect of nanosized YSZ to explore key techniques to decrease the operating temperature. YSZ nanoparticles ranging from 2 to 4 nm were synthesized with oleate groups by the hydrothermal method at various oleate/metal ion ratios (Ole/M = 1.00, 0.75, and 0.50). The nanoparticles were sintered, and the ionic conductivities were evaluated. The 1.00 Ole/M sample exhibited high dispersibility in cyclohexane and showed a nearly monodispersed distribution. The other samples possessed agglomerated nanoparticles. The sintered YSZ nanoparticles had densities of 3.36-2.80 g/cm3 and ionic conductivities of 2.52-1.16 mS/cm at 750 °C, which are higher than those of commercial 8 mol % YSZ. Furthermore, the sintered YSZ nanoparticles exhibited higher activation energies than the commercial samples in the lower temperature range (550-650 °C). The ionic conductivity enhancement despite the high activation energy is likely due to the increased grain boundary volume. This study demonstrated the successful production of YSZ with high ionic conductivity and sinterability upon sintering at 1050 °C using YSZ nanoparticles.

Noble metal-free 0D-1D CoOx/Mn0.3Cd0.7S nanocomposites for efficient visible-light hydrogen production

Here, a series of MnxCd1-xS sosoloid composite photocatalysts with visible-light activity were first prepared by a solvothermal process. The element ratio of Cd2+ to Mn2+ was optimized to be Mn0.3Cd0.7S in MnxCd1-xS sosoloid on account of its photocatalytic activity for H2 evolution from H2O in response to visible light excitation. And on this basis, the CoOx nanopariticles were loaded on the surface of Mn0.3Cd0.7S sosoloid composite to obtain a binary p-n heterojunction of CoOx/Mn0.3Cd0.7S composite through a facile impregnation process and a high temperature sintering procedure. Benefitting from the synergistic effect of the built-in electric field, binary p-n heterojunction structure, and rearrange of the Fermi level equilibrium, the as-synthesized CoOx/Mn0.3Cd0.7S composite presents a highly enhanced photocatalytic activity for hydrogen production from H2O in response to visible light excitation, which is demonstrated to be 53.4 and 4.0 times higher than that of the primitive CdS and Mn0.3Cd0.7S, respectively. Furthermore, after 4 times circles of photocatalytic H2 production tests, the CoOx/Mn0.3Cd0.7S composite still keeps 92.0 % of the original photocatalytic activity. Considering its reasonable photochemistry stability and excellent photocatalytic activity for hydrogen evolution from H2O under with visible light excitation, the as-synthesized CoOx/Mn0.3Cd0.7S composite has potential applications in solar hydrogen production areas.

Effects of Bi2O3 doping on structural and electrical properties of Ce0.8Sm0.2O1.9 electrolyte for solid oxide fuel cells

The study investigates the impact of Bi2O3 doping on the crystal structure, density, and ionic conductivity of Ce0.8Sm0.2O1.9, a type of samarium-doped ceria oxide (SDC). The material is intended for use as a solid electrolyte in intermediate temperature solid oxide fuel cells (IT-SOFCs). The SDC-based electrolyte was created using the auto-combustion technique, with various molar ratios of Bi2O3. Phase compositions, microstructure, and ionic conductivity of all ceria ceramics were analysed using XRD, SEM and impedance analyses, respectively. The language is formal, clear, objective, and value-neutral, using high-level, standard language with consistent technical terms. Grammar, spelling, and punctuation are correct. Consistent citation and footnote style are maintained. The samples are single-phase ceramics that crystallise into a cubic fluorite type structure with space group Fm-3 m, as confirmed by the X-ray diffraction pattern. Technical abbreviations are explained. The structure ensures a logical flow of information with causal connections between statements. No filler words or biased language are used. SDC/Bi2O3 composite powders exhibit high sintering activity. The relative density of all samples sintered at 1300 ºC for 5 h was more than 96%, which is higher than that achieved by pure SDC electrolyte sintered at 1400 ºC (94.06%). Electrochemical performance results demonstrate that adding an appropriate amount of Bi2O3 can significantly enhance the conductivity of SDC materials. The SDC-based electrolyte containing 9 mol% of Bi2O3 (SDCB9) demonstrates the maximum conductivity of 43.5 mS·cm−1 at 800 °C, surpassing that of pure SDC which measures 26.86 mS·cm−1.

Maximizing Efficiency and Affordability with Ceramic Membranes for Enzyme Immobilization

AbstractLow‐cost ceramic microfiltration membranes were explored for immobilizing lipases. Expensive commercial ceramics (e.g., alumina, zirconia) have advantages like chemical robustness, but high sintering temperatures limit their usability. To overcome this, researchers used Fuller's earth clay with rice husk ash to create cost‐effective membranes. However, fewer reactive sites on ceramic surfaces hinder enzyme immobilization. To address this, 3‐aminopropyltriethoxysilane and glutaraldehyde activated the membrane for covalent lipase binding. The immobilized membrane retained activity for over five 1‐h reaction cycles with a minimal performance decline of around 60 %. After five cycles, it retained over 40 % of the initial activity. These results show promise for using low‐cost ceramic membranes in various industries, such as in food, beverages, pharmaceuticals, and chemical production.

Cold-sintering and Li doped ZnO sintering aid for the densification of BaZr0.7Ce0.2Y0.1O3-δ proton conducting ceramics

Proton conducting BaZr0.9-xCexY0.1O3-δ electrolytes have been intensively investigated in the past years. The zirconium rich stoichiometry of this perovskite type material shows good chemical stability coupled with high proton conductivity. However, this material remains highly refractory. Therefore, high sintering temperatures (1800 °C) are required to fully densify the electrolyte layer. This study focuses on using different sintering strategies, such as cold-sintering and sintering aids, during the fabrication of the electrolyte to decrease the sintering temperature. After various densification protocols, the electrical conductivity of the zirconate (BaZr0.7Ce0.2Y0.1O3-δ) electrolytes are compared to study the influence of the densification process on the bulk, grain boundary and total conductivity of the electrolyte layer.

Flash sintering of Lead Zirconate Titanate (PZT) with minimal lead oxide loss and enhanced dielectric properties

Generally, a high temperature (>1100°C) is required to sinter Lead Zirconate Titanate (PZT) ceramics. Such a high sintering temperature results in significant lead oxide evaporation which is a major environmental problem due to its toxicity. In this work, we have performed flash sintering of Lead zirconate Titanate (Pb (Zr0.5Ti0.5) O3)) using a novel setup and compared the phase and microstructural evolution, dielectric, piezoelectric properties and lead loss with conventionally sintered Lead zirconate Titanate (PZT). The lead oxide evaporation has been reduced by 5–10 times compared to conventionally sintered PZT. Results also show that the flash-sintered samples' dielectric constant is about ∼ six times higher than the conventionally sintered samples with similar dielectric loss. Ferroelectric and piezoelectric properties of flash sintered PZT on the other hand are lower than conventionally sintered PZT. The mechanisms behind the anomalous properties are discussed using structural and microstructural observations.

Influences of Sintering Temperature and Pressure on Microstructure, Optical and Mechanical Properties of Hot-Pressing-Sintered Gd2O3–MgO Nanocomposites

Low temperature combined with high application pressure sintering technology is one of effective approaches to fabricate ceramics with fine microstructure. We reported that the Gd2O3–MgO nanocomposite ceramics were obtained by hot-pressing sintering using nanopowders derived from sol–gel combustion method in this paper. The high optical transmittance (80.1%–83.5%) over 2-6 μm and the high values for Vickers hardness (11.1 ± 0.3 GPa) and bending strength (192.6 ± 8.1 MPa) were obtained by hot-pressing sintering at low sintering temperature (1300 μC) and high application pressure (65 MPa).