Sintering Conditions Research Articles

Crystalline structure and dielectric relaxor behavior of MnO2-modified 0.8BaTiO3-0.2BiScO3 ceramics for energy storage application

Based on the synergistic roles of defect dipoles and MnO2 sintering aid, 0.8BaTiO3-0.2BiScO3 (BTBS0.2) ceramics with and without 0.3 wt% MnO2 were prepared by a solid-phase reaction route. The impacts of MnO2 dopant and sintering conditions on the crystalline structure, micro-morphology, dielectric, and energy storage properties were investigated in detail. The X-ray diffraction (XRD) and Raman results demonstrate the coexistence of tetragonal (T) and pseudo-cubic (pC) phases. The increased pC phase content caused by MnO2 modification is beneficial for the improvement of the relaxation degree. The O 1s fine spectra of X-ray photoelectron spectroscopy (XPS) confirms a remarkable increase in the concentration of oxygen vacancy due to the acceptor Mn dopant, indicating the valence changes of Mn ions from Mn4+ to Mn3+/Mn2+. The reduced dielectric loss is induced by the improved density and the pinning effect from the defect dipoles, thereby yielding a higher Eb. An optimal energy density of Wrec = 0.70 J/cm3 with a high energy efficiency of η = 95.8% at 140 kV/cm was realized in the BTBS0.2+Mn ceramic composition sintered at 1300 °C. Moreover, the ceramic also exhibits good temperature stability (30-120 °C). Therefore, the BTBS0.2+Mn ceramics have a promising application prospect in the energy storage field.

Synthesis and characterization of Cobalt-chromium based alloys via spark plasma sintering for biomedical applications

The present study investigates the impact of Mo and Nb on the characteristics of CoCr sintered alloys, with a specific focus on their potential for biomedical applications. Cobalt-chromium-based alloys (namely, Co-Cr-2.5Mo-2.5 Nb, Co-Cr-3Mo-3 Nb, and Co-Cr-3.5Mo-3.5 Nb) were fabricated using sintering conditions comprising a heating rate of 200 °C/min, pressure of 50 MPa, temperature of 1100 °C, and a dwell period of 15 minutes. The findings indicated that the CoCr alloy, when supplemented with Mo and Nb, exhibited a singular-phase composition consisting mostly of a face-centered cubic (FCC) core comprised of gamma-Co, accompanied by a minor proportion of a hexagonal close-packed (HCP) solid solution matrix known as epsilon-Co, and interspersed with precipitates. The inclusion of Co-Cr-3Mo-3 Nb alloy composition resulted in the highest relative density of 97.56 % compared to other alloy compositions, indicating its optimum alloying properties. The Co-Cr-3Mo-3 Nb alloy had the maximum polarization resistance of 522.52 Ω, indicating a strong resistance to corrosion. Additionally, it displayed the least corrosion rate of 1.5904 mm/year. The ternary alloy consisting of Co-Cr-3.5Mo-3.5 Nb demonstrated superior resistance to the applied indentation stress, as shown by its minimal maximum penetration depth of 372.23 nm and the lowest average coefficient of friction (COF) values.

A theoretical and experimental study of phase formation in Ti–CuO powder mixtures under reactive sintering conditions

A thermokinetic model of composite synthesis from Ti and CuO powders is suggested. The numerical modeling leads to nonequilibrium composition of the product that qualitatively agrees with the experimental data.

Creating Single-Crystalline β-CaSiO3 for High-Performance Dielectric Packaging Substrate.

β-CaSiO3 based glass-ceramics are among the most reliable materials for electronic packaging. However, developing a CaSiO3 glass-ceramic substrate with both high strength (>230MPa) and low dielectric constant (<5) remains challenging due to its polycrystalline nature. The present work has succeeded in synthesizing single-crystalline β-CaSiO3 for a high-performance glass-ceramic substrate. This is accomplished by introducing Al3+ into the CaO-B2O3-SiO2 glass system, and by optimizing the sintering condition. Al3+ doping facilitates a heterogeneous network structure that energetically favors the precipitation of polycrystalline particles, including nanosized β-CaSiO3 crystals and sub-nanosized α-CaSiO3 crystals. As the sintering temperature increases, the nano α-CaSiO3 crystals (2-10nm) are gradually absorbed by the β-CaSiO3 crystals. Through atomic rearrangement, α-CaSiO3 crystals transform into micrometer-sized single crystal β-CaSiO3 (1-2µm) with layered structure. The low temperature co-fired β-CaSiO3 glass-ceramics exhibit exceptional properties, including a low dielectric constant of 4.04, a low dielectric loss of 3.15 × 10-3 at 15GHz, and a high flexural strength of 256MPa. This work provides a new strategy for fabricating high-performance single-crystalline glass-ceramics for electronic packaging and other applications.

Experimental research of the regularities of iron-bearing ore desulfurization for the temperature conditions of liquid phase sintering

Experimental research of the regularities of iron-bearing ore desulfurization for the temperature conditions of liquid phase sintering

Activation and development of direct plasma spark sintering and this method after the synthesis of combustion of ceramic-metal compositions through different mixtures of metal melts and/or intermetallic compounds

The article shows the effect of different mixtures melts of metals and/or intermetallic compounds with various oxide, non-oxide additives, obtained solid solutions of metallic phases during spark plasma sintering, spark plasma sintering after combustion synthesis on the phase composition, micrstructure, grains sizes of crystalline phases, relative density, linear shrinkage, microstructural featres of boundary layers, paths of microcracks, physical-mechanical properties, values of standart erors of properties of samples. Synthesized powders of h-BN, B4C, NiTi, NiZr are characterisized by high intensity of crystallization of h-BN, B4C, NiTi, NiZr. Sintered by spark plasma method c-ZrO2, c-BC2N at pressing loadings 35 MPa and 1400 oC, 5 GPa and 2327 oC in boron melt show evoluted crystalli-zation of c-ZrO2, с-BC2N phases, respectively, crystalline, uniform and dense microstructures. Obtained by combustion synthesis powder shows multi-phase composition with various crystallization of phases. Sintered by direct spark plasma method samples show evoluted mullitization, crystallization of c-ZrO2, solid solutions of metallic phases, but in the samples, obtained by spark plasma method in different sintering conditions after combustion synthesis are visible crystalline, multi-intensive phases. The samples show crystalline, multi-uniform and multi-dense microstructures, variously dispersed grains of crystalline phases. Sintered samples are differ by the relative density, linear shrikage, density, uniformity, width, path of boundary layers and propagating microcracks across these boundary layers, the resistance to the cracking, values of physical-mechanical properties, values of standart errors of properties of samples.

Preparation and characterisation of zirconia/hydroxyapatite bioactive composites as potential dental implants

In dental implants, zirconia is well-known as a crown material due to its excellent acid and base resistances and appearance close to natural teeth. In addition, its extraordinary mechanical properties render zirconia to be a potential candidate as an implant component of a whole implanted tooth, if its biocompatibility can be improved to promote adhesion to natural hard tissues. This study aims to enhance the bioactivity of zirconia with the aim of improving its integration with gum bone. Hydroxyapatite is the major component of natural bone and is thus selected as the modifier to improve the bioactivity of zirconia. A series of zirconia/hydroxyapatite composites with varied compositions were prepared under different conditions in order to find the optimal composites for the target application. Various analytical technologies and mechanical tests are employed to characterise the structure and properties of resultant composites. Results show that the component ratio and sintering temperature have a significant influence on the composite properties. An increase in hydroxyapatite component tends to enhance bioactivity but decline mechanical strength. Composites containing 10 wt% of hydroxyapatite maintain sufficient mechanical strength under the optimal sintering conditions whilst possessing excellent bioactivity, demonstrating that hydroxyapatite-modified zirconia has the potential as dental implant materials. Sintering results suggest that mechanical strength is obtained at 1400 °C for 2 h for the composite containing 10 wt% of hydroxyapatite.

Reconstruction of LATP-LT composite solid electrolyte and analysis of Li+ conduction mechanism using 3D CT

Li1+xAlxTi2-x(PO4)3 (LATP) is a highly promising solid-state electrolyte, known for its high lithium-ion conductivity and stability at room temperature. This study successfully prepared LATP-LT composite solid-state electrolytes by combining LATP with Li2O-TeO2 (LT) glass, utilizing the molten state of the glass at high temperatures. The investigation focused on the effects of different ratios and sintering conditions on the performance of the LATP-LT composites. Results indicate that an appropriate amount of LT enhances the material's sinterability, facilitating continuous lithium-ion conductivity while inhibiting the diffusion of lithium dendrites within the pores. The LATP-LT composite solid electrolyte achieved an ionic conductivity of 1.81×10-4 S/cm at room temperature. Thus, selecting an optimal concentration of LT can serve as a breakthrough in the development of all-solid-state lithium-ion batteries, advancing the field of solid-state electrolytes.

Preparation of eco-friendly and high-strength ceramsite by granite scraps, granite fine mud, and phosphogypsum: Response surface methodology optimization, environmental safety assessment

Granite scraps (GS), Granite fine mud (GFM), and phosphogypsum (PG) are solid wastes containing harmful substances produced during the processing of granite and the production of phosphate fertilizer. Their resourceful and harmless utilization holds great significance in reducing environmental pollution. This study explores the preparation of eco-friendly and high-strength ceramsite using GS as the primary material, GFM as the binder, and PG as the regulator. The performance of ceramsite was studied by conducting single-factor experiments to examine the impact of the GS, GFM, and PG mass ratios. The Box-Behnken response surface methodology was utilized to optimize the effect of sintering conditions on the strength of ceramsite. The results suggested that the properties of the ceramsite are affected by the material ratios. The sintering temperature and keeping time notably influence the strength of ceramsite. Under optimal preparation conditions, the ceramsite achieved a bulk density of 1085.40kg/m3, apparent density of 2253.63kg/m3, 1-h water absorption of 0.13%, hydrochloric acid soluble rate of 0.016%, and compressive strength of 34.52MPa. Importantly, high-temperature sintering plays an essential role in fixing heavy metals and reducing the ecological risk level of heavy metals in ceramsite, which ensures excellent environmental performance and application prospects for ceramsite.

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

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

Impact of Sintering Aid Type and Content on the Mechanical Properties of Digital Light Processing 3D-Printed Si3N4 Ceramics.

Digital light processing (DLP) 3D-printed Si₃N₄ ceramics, known for their exceptional performance, offer distinct advantages in meeting the high-strength and complex structural demands of industries such as aerospace, semiconductors, healthcare, automotive, energy, and machinery. However, due to Si₃N₄'s strong chemical stability, low diffusion rate, low self-sintering ability, and high melting point, achieving densification under conventional sintering conditions is challenging. As a result, sintering additives are essential to promote the sintering process, lower the sintering temperature, improve densification, and enhance performance. In this study, 45 vol% Si₃N₄ slurries were prepared using DLP 3D printing technology, incorporating nine different combinations of sintering additives, including aluminum oxide (Al2O3), yttrium oxide (Y2O3), and aluminum nitride (AlN), in various ratios with Si3N4. The slurries were then sintered at 1800 °C for 2 h under a 1 MPa N2 atmosphere. Additionally, the phase composition, microstructure, grain distribution, and crack propagation of the materials. The results showed that a Si3N4 to Al2O3 and Y2O3 ratio of 95:2.5:2.5 produced elongated β-Si3N4 grain structures and enhanced density, achieving a maximum Vickers hardness of 12.88 ± 0.52 GPa. Additionally, the synergistic toughening effect of the rod-like β-Si3N4 grains and sintering aids significantly improved the fracture toughness of the Si3N4 ceramic matrix, with a flexural strength of 540.63 ± 10.05 MPa and a fracture toughness of 4.92 ± 0.07 MPa·m1/2. This study lays the foundation for the future application of 3D-printed Si3N4 ceramics, optimization of sintering aid combinations at different ratios, and performance enhancement in extreme environments.

Effects of Multiple Factors on the Compressive Strength of Porous Ceramsite Prepared from Secondary Aluminum Dross.

Aluminum is one of the most in-demand nonferrous metals in the world. The secondary aluminum dross (SAD) produced during aluminum smelting is a type of solid waste that urgently requires disposal. SAD, municipal solid waste incineration fly ash, and bottom slag were used as raw materials to prepare porous ceramsite in a laboratory in this study. Multi-factor design experiments were then used to explore the influence of the sintering condition on the compressive strength to provide a basis for ceramsite preparation using SAD. The results showed that, within a certain variation range, the levels of each factor showed overall positive correlations with the ceramsite compressive strength. The contributions of the ceramsite particle size, the silicon-aluminum ratio (Si/Al), the sintering temperature, and the sintering time to the compressive strength of the porous ceramsite then decreased. The factors had a synergistic effect. The interactive effect of multiple factors on the porous ceramsite compressive strength rose with an increase in the particle size and Si/Al ratio. The average compressive strength of the porous ceramsite prepared in this study was 4.06 ± 3.71 MPa, and the maximum compressive strength was 14.13 MPa. The highest ceramsite compressive strength was achieved under a sintering temperature of 1270 °C, a particle size of 2 cm, a sintering time of 30 min, and a silicon-aluminum ratio of 1.5. In addition, there was a reaction relationship between the multiple factors involved in the sintering of the SAD-based porous ceramsite. Pilot or industrial tests should be conducted in the future based on these experiments and the intended ceramsite use.

Prediction of Li Ion Conductivity Using a Denoising Autoencoder and an Attention for Experimental Data

While all-solid-state batteries composed of inorganic materials are attractive in terms of safety, rate performance is still insufficient. One of the causes is rather poor ionic conductivity of the solid electrolytes, and new high ionic conductive materials are required. Li containing NASICON-type materials are one of candidates due to its high Li ion conductivity. Many efforts have been devoted to improve their Li ion conductivities by changing composition and/or sintering conditions. Meantime, many experimental data, such as optical spectroscopy, diffraction, and so forth, are accompanied in the process of measurements for ionic conductivities. Making a link between ionic conductivity and all the analytical outputs may lead to good guideline for designing materials, though interpretation of analytical output is often difficult. In this study, we focused on Li1.45Ca0.15Zr1.85Si015P2.85O12 ( LCZSP ) [2] doped with Ca and Si in LiZr2(PO4)3, which belongs to NASICON-type solid electrolyte that exhibits high lithium-ion conductivity and stability against metallic lithium[1]. We reported that the conductivities of this material change depending on the sintering conditions, where we performed 54 synthesis, XRD and Li ion conductivity measurements.[3] Revisiting these experimental data, we tried to make link between XRD and conductivities through machine learning. Fig. 1 is the schematic representation of the present machine learning model based on deep neural network techniques. An XRD pattern contains noise derived from device, human factors, and so forth. To reduce the influence of noise in the XRD measurement data, a denoising autoencoder was utilized in the model. In addition, XRD patterns are reduced to a two-dimensional representation by the denoising autoencoder and make a link from encoded variables to the ionic conductivities( The blue and yellow areas in Fig. 1 ). The use of the denoising autoencoder enables the construction of a more general model for experimental data. Furthermore, we aimed to enhance the prediction accuracy and interpretability by introducing an attention mechanism that learns the points of interest in the spectrum ( The yellow-green area in Fig. 1 ). Here, we successfully fit the ionic conductivity through autoencoder derived variables, and confirm an improvement of fitting results by implementation of the attention mechanism. The details will be presented in our poster session.

Development of Nasicon-Type Electrolytes Using Combination of Experimental Techniques and Materials Informatics

Introduction Research and development of large lithium-ion batteries is essential for new societal infrastructures such as electric vehicles, aircraft and smart grids. Replacing the liquid electrolyte of conventional lithium-ion batteries with solid electrolytes not only makes them less prone to ignition, but also increases their energy density. Sulfide, chloride and oxide systems are known as solid electrolytes. Sulphide and chloride types have high lithium-ion conductivity but are generally unstable in air. Therefore, there is an urgent need to develop oxide-based solid electrolytes that are stable in air, and the Na superconductor (NASICON) type LiZr2(PO4)3 (LZP) is a candidate oxide-based solid electrolyte for all-solid-state lithium-ion batteries. However, its ionic conductivity is inadequate. We have therefore investigated co-doped LZP (Li1+x+2yCayZr2-ySixP3-xO12), in which Zr is partially replaced by Ca and P by Si. First, a total of 49 compositions were synthesized and their crystal structure, relative density and lithium-ion conductivity were experimentally evaluated [1]. Since lithium-ion conductivity is also affected by microstructural properties such as density, morphology and elemental distribution of the sintered pellets, the conductivity can be improved by controlling process parameters such as heating conditions during the solid-state reaction. Therefore, the material was synthesized in a solid-state reaction under different heating conditions in two stages and the effect of the heating conditions on the microstructural properties of the sintered pellets was investigated [2].Such thorough sample preparation requires considerable time, effort and cost, and consumes a large amount of energy and resources. Therefore, AI-based optimization methods called Bayesian Optimization (BO) have attracted attention. Bayesian optimizations is a method that uses statistical inference to select the next candidate to explore and find the best performing sample with the least number of samples. Using the experimental data obtained in our study, we demonstrated whether the BO algorithm can 'efficiently' find the optimal composition and heating conditions to achieve the highest ionic conductivity of such materials. Experimental Li1+x+2yCayZr2-ySixP3-xO12 was synthesized by a conventional solid-state reaction using two-stage heating. The crystalline phase of the samples was determined by X-ray diffraction (XRD). The micro morphology of the samples was evaluated by scanning electron microscopy. The ionic conductivity of the pellets was measured by AC impedance.BO was performed to evaluate the efficiency of the optimized composition or heating conditions to obtain the highest ionic conductivity of the experimentally evaluated samples. Conductivity at 30 °C was the objective. Results and discussion The Li1.45Ca0.15Zr1.85S0.15P2.75O12 sample heated at 1050°C and 1250°C gave the highest lithium-ion conductivity of 3.3 x 10-5 S/cm at 30°C. Investigation of the sintered samples showed that composition and heating conditions affected the crystalline phase, density, microstructure and elemental distribution. The relationship between ionic conductivity and these observations was so complex that it was difficult to determine the optimum composition and heating conditions intuitively from a few experiments. Figure 1 shows the number of experiments required to find (a) the optimal composition and (b) the optimal heating conditions with 80%, 90% and 100% probability using BO or random search. The results show that using BO can find the optimum composition or optimum sintering conditions in about half the number of trials compared to a random search. Thus, Bayesian optimization has been shown to be effective in finding the optimum composition or process conditions of a material.

Assessing ceramic powder quality by activated Sinterability Test: The case of UO2

Ceramics fail by brittle fracture due to flaws and affect process yield. The starting material is usually in powder form. UO2 pellets are obtained by pressing powder, sintering and finish grinding. Large powder blends are usually accepted for pressing and sintering after evaluating a small representative powder sample by conducting a sinterability test under regular process conditions. On the other hand, this paper recommends activated sintering conditions, such as those achieved with additives or sintering atmosphere control. Many defects in ceramics have origins in the powder. For example, large hard agglomerates in the powder can cause packing difficulties in pressing. Defects that are not detected in normal sintering may be noticed more readily in activated sintering due to defect amplification. In sintering, open porosity ceases after reaching a density of ∼93 % TD. The residual closed porosity tends to shrink on further sintering. The temperature at which open porosity or permeability is lost shifts to a lower temperature in activated sintering. Yet, activated sintering is to be carried out at conventional high sintering temperature, to be able to amplify and expose pellet defects due to powder. Desintering is a result of large sized packing defects in the green body and premature loss of open porosity in the course of sintering. A descriptive model of desintering is suggested that takes into account powder specific surface area, sintering additive and atmosphere. There is no desintering when green microstructure is homogeneous with no density gradients and with uniformly distributed fine voids that shrink and close during sintering. A high-quality powder sample is one that results in high pelleting yield both in conventional and activated sintering. The low temperature sintering process for UO2 manufacture that did not progress due to thermal stability concerns in nuclear reactor, may be revived to lower nuclear fuel costs.

Powder casting of polyetheretherketone and polyphenylene sulfone: Sintering

Systematic studies of the influence of the basic powder characteristics and its sintering conditions on the physical and mechanical properties of samples intended for the implementation of the technology of powder injection molding of products from typical heat-resistant high performance engineering polymers - crystallizing polyetheretherketone (PEEK) and amorphous polyphenylene sulfone (PPSu) - were carried out. Polymers with different MW were synthesized as initial materials and powders with different sizes and bulk density were obtained. The influence of these parameters on the nature of powder sinterability and, as a consequence, on their elastic modulus and tensile strength was shown. Optimum characteristics for bulk density and sintering temperature were established, which provide maximum values of mechanical characteristics of the molded samples. The results of the fundamental research conducted allowed us to produce two typical products for biomedicine - an intervertebral cage (an implant replacing a removed vertebra) and a blood dialyzer part.

Steel Chips as a Raw Material for MEX

In recent years, metal chip powders obtained from solid-state processes have shown great potential as a sustainable raw material for powder technologies. The material and fragmentation process of the chips has a significant role in the final characteristics of the powder particles, such as size and particle size distribution, shape, surface, and structure, which are essential parameters to consider when converting chips to powder for applications. However, tool steel chips as a powder raw material have not yet been significantly studied. In this study, the steel chips were from machining AISI H13 steel and the milling process used a ball mill, and the challenge was to obtain powder particle sizes of around 20 µm with suitable properties from the application of envisaged material extrusion (MEX). A comparison study with the commercial raw material for MEX, such as powder metal filament extrusion, was performed. This study highlights the behaviors of chip powders during all steps of MEX, namely, feedstock and filament production, 3D object shaping, thermal de-binding, and sintering. A comparison of the mixture based on powder from chips and commercial powders for MEX was performed after evaluating the mixing torque of the powder and the system of binders and additives suitable for the rheological characteristics required for an extrusion mixture, and optimizing the binder removal and the sintering conditions. The 3D objects resulting from chip powders had a refined microstructure, showing an increase of 15% in the microhardness when compared with the those resulting from commercial powders.

Role of co-doping (Sm3+ and Nb5+) and Sintering Conditions on the Dielectric Properties of CaCu3Ti4O12 Ceramics

This research delves into the impact of Sm3+ and Nb5+ co–doping and the effect of sintering temperature on the grain size and the dielectric properties of CaCu3Ti4O12 (CCTO) ceramics synthesized via the sol–gel process. The Rietveld refinement provided detailed structural parameters, including atomic positions, bond lengths, bond angles, and R–factors, with a goodness of fit below 2% with no secondary phases. The expected core levels for Ca 2p, Sm 3d, Cu 2p, Ti 2p, Nb 3d, and O 1s were verified by XPS analysis, suggesting that these materials were present in their expected oxidation states. As the sintering temperature is increased, the average grain size grew from 0.61 ± 0.08 μm to 2.38 ± 0.32 μm. Notably, the sample sintered at 1050 °C exhibited huge dielectric permittivity (ε' ≈ 105) with good stability in the wide frequency range (102–105 Hz) with significantly low dielectric loss. The complex impedance analysis was studied to separate the contributions of grain and grain boundary resistances while the Nyquist plot revealed that the Rgb ranged from 4.26 × 103 to 4.95 × 106 Ω. The AC conductivities of all the ceramics displayed semiconducting characteristics, exhibiting a frequency dependence that conforms to Jonscher's power law. The observed performance of the dielectric of the ceramic can be ascribed to the Internal Barrier Layer Capacitance (IBLC) model.

Mo site nonstoichiometry engineering: An effective strategy to enhance microwave dielectric properties of Al2Mo3+xO12 ceramic

Al2Mo3O12 materials exhibit remarkable potential in Low-Temperature Co-fired Ceramics devices due to their low relative permittivity and favorable low-temperature sintering properties; nevertheless, its Q×f value is not satisfactory. In this study, non-stoichiometric modification engineering of Mo site ions was designed, to investigate the effects of non-stoichiometric design on structural evolution and microwave dielectric responses of Al2Mo3+xO12 ceramic. The results demonstrate that the excessive contents of Mo6+ cations within the range of x = 0.02 to 0.06 leads to the formation of a monoclinic Al2Mo3O12 solid solution ceramic, different shrinkage of the unit cell cause structural distortion, which can be confirmed by the normalized variations of chemical bonds and Raman spectra. Both the structural evolution and sintering conditions contribute to the enhancement of microwave dielectric properties. Specifically, based on dielectric theory of chemical bonds, the average bond ionicity primarily affects the high frequency micro-polarizability of Al2Mo3+xO12 ceramic; the inherent dielectric loss is affected by the lattice stability, as indicated by the variation of total lattice energy. Also, the outer factors including bulk density and average crystallite size cannot be ignored. Through the inherent dielectric response analysis method of Al2Mo3.04O12 ceramic, the specific influence of each phonon mode to the inherent dielectric response were calculated, revealing that the phonon mode at 159.84 cm-1 provides significant contributions to the dielectric properties. It is found that non-stoichiometry design on Mo site effectively improves the Q×f value of Al2Mo3+xO12 material. Typically, the microwave dielectric properties of Al2Mo3+xO12 (x = 0.04) ceramic are: εr = 6.19, Q×f = 63216 GHz (@13.87 GHz), when sintered at 800 oC.

Evaluation of Zn-Mg alloys: Microstructural and mechanical properties under low sintering condition

Evaluation of Zn-Mg alloys: Microstructural and mechanical properties under low sintering condition