Electronic Ceramics Research Articles

Microstructure formation mechanisms and property regulation methods during ceramic additive manufacturing

Anisotropic surface lamellar defects, dimensional shrinkage, and bending strength are important scientific issues that constrain vat photopolymerization additive manufacturing of biological, electronic, and core ceramics with high precision and complex structures. Through the single-factor experiment of photoinitiator concentration, average particle size, volume fraction, and refractive index constant in ceramic-resin slurry, this work studies the photopolymerization characteristics and profile curves, surface lamellar defects, and crosslinking density, verifies the reliability of the photopolymerization profile equations affected by the slurry composition, and acquires the anisotropic property formation mechanisms and control methods. The single-point scanning photopolymerization profile shape is parabolic, resulting in x-, y-, and z-direction lamellar defects before and after sintering (1550 °C), with no obvious weakening. After the quantitative description of the lamellar defects, the average surface roughnesses before and after sintering of the green body are 6.82 and 4.92 μm, respectively. Additionally, the laser energy attenuation along the penetration direction induces a gradient distribution of crosslinking density in the photopolymerization profile region. The crosslinking density gradient distribution of the decay from the slurry surface toward the depth direction is influenced by the slurry component concentration, leading to a gradient of cured powder concentration, which induces anisotropic behaviors. Through the crosslinking density controlling, the average bending strength in x(y) and z directions is increased by 63.19 % (46 %), the difference in anisotropic strength is reduced by 22.55 %, and the dimensional shrinkage difference of x and z directions is reduced by 48.32 %. This provides a theoretical and experimental research basis for ceramic vat photopolymerization with high dimensional accuracy, excellent performance, and morphology control.

Improving the suppression of charge movement by porous chromium oxide coating

A chromium trioxide coating was prepared on the surface of electronic ceramics by screen printing, and solid-phase sintering was carried out at 1350 °C. The surface roughness and surface resistance characteristics of composite coatings with different chromium trioxide contents were studied. The analysis results indicate that the average thickness of Cr2O3 coating is about 19.89 μm. The main crystal phase is (Al0.9Cr0.1)2O3. SEM shows that the surface "pores" and surface roughness of the coating change with the content of Cr2O3. AFM shows that when the Cr2O3 content in the coating is 0.0921 mol, the surface roughness changes the most, and the corresponding surface resistivity of Al2O3 insulating ceramics decreases to the lowest, from 1016 Ω to 1012 Ω. An increase in surface roughness can lead to changes in the incidence angle of electrons, reducing the probability of electron surface collision. The lower the surface resistivity, the better the high-voltage breakdown resistance of vacuum ceramic devices, thereby improving the surface flashover performance of ceramics.

Novel NaNbO3-based relaxors featuring ultrahigh energy storage performance

Ferroelectric ceramics with ultrahigh power density and fast charging/discharging are attracting increasing attention. The practical application of most antiferroelectric ceramics in current electronics is significantly limited by their poor recoverable energy storage density. Here, a novel system ceramic of (1-x) Na0.84Ca0.16Nb0.84Ti0.16O3-xBiZn2/3Nb1/3O3 (NCNT-xBZN) solid solutions, possessing a giant Wrec∼7.05 J cm−3 and excellent conversion efficiency (η)∼83.7% under 53 kV mm−1, was synthesized to exhibit superior stability with changing temperature, frequency and fatigue behavior, together with the large current density (CD=571.8 A cm−2), ultrahigh power density (PD=85.7 MW cm−3) and ultrafast discharge rate (∼200 ns). These outstanding properties are attributed to the phase transformation from the AFE R to the FE Q phase, accompanied by the smashing of sub-microdomains into polar nanoregions, as the BZN content raises. The experimental results disclose that the synergistic effect of the highly dynamic response of polar nanoregions and the local lattice distortion arising from the disruption of long-range polar ordering by heterovalent ion filling generates a delayed saturation polarization with a strong relaxor behavior, thereby optimizing the energy storage density. The unique combination, together with a simple synthesis strategy, offers a refreshing strategy for the development of dielectric materials.

A novel linear temperature thermistor in the xAl2O3-(1-x)CdSnO3 system

Negative Temperature Coefficient (NTC) thermistors, known for their high sensitivity and fast response, find wide applications in national economy, military, aerospace and various other fields. The study of NTC thermistors with linear temperature-resistance is of great significance in streamlining circuit designs and developing high-performance electronic ceramics. This study focuses on the synthesis of a linear thermistor material in xAl2O3-(1-x)CdSnO3 system by a solid-phase reaction method. Through the introduction of th high-resistance Al2O3 phase, a three-dimensional conductive network is established with Al2O3 and CdSnO3, resulting in the acquisition of linear electrical properties. These properties have exhibited excellent linear NTC variation within the temperature range of 308 K–458 K. Notably, at x = 0.2, the thermistor shows the highest linearity (R2 = 0.9984). Additionally, the complex impedance spectral analysis has helped build resistive and capacitive conductivity models revealing the linearization mechanisms.

Low-temperature joining of alumina ceramic and nickel by Al-Ni self-propagating nanofoil

To meet the requirements of alumina ceramics in delicate electronics, there is an urgent need for a low-temperature bonding technology that can realize a good combination of alumina and metal. In this work, alumina ceramics and nickel metals were successfully connected at a low temperature (25–150 °C) by Al-Ni self-propagating nanofoil as a heat source. The interface microstructure and element distributions of the solder joints from cross-section and fracture surface were investigated. In addition, the solder joint formation process was simulated by finite element analysis and molecular dynamics. These results showed that their shear strengths could be continuously improved with the growing temperature, which were 17.4 MPa (room temperature, 25 °C), 19.5 MPa (50 °C), 22.9 MPa (100 °C) and 25.69 MPa (150 °C). The Al2O3/Al-Ni nanofoil/Ni solder joints were prone to crack at the corner and boundary at Al2O3/solder interfaces due to the stress concentration. Moreover, the increase in ambient temperature not only raises the melting time and transient temperature during the self-propagating reaction, but also improves the interdiffusion of Ni and Sn atoms at the Ni/Sn interfaces.

New linear high-temperature thermistors based on the xAl2O3-(1-x)CaMnO3 ceramics

It is very important for a thermistor to have linear electrical properties, which can effectively reduce the complexity of circuit design. Phase structure modulation through introducing a second phase is crucial to achieve high performance electronic ceramics. Herein, new linear high-temperature thermistors based on the xAl2O3-(1-x)CaMnO3 ceramics were synthesized by the solid phase reaction method. With increasing Al2O3 content, CaMn2O4 and CaAl2O4 phase were observed, which formed internal conducting network and induced linear electrical properties. The ceramics exhibited negative temperature coefficient (NTC) thermistor characteristics in the temperature range of 523 K–1173 K. Their resistance-temperature (R-T) relationship displayed a good linear characteristic, especially for x = 0.3, which showed the highest linearity (R2: 0.9984) in the temperature range of 523 K–1173 K, covering medium to high temperature region. The mechanism of linear electrical properties was explained by a parallel conductive model in combination with complex impedance analysis. This approach could be generalized for designing linear high-temperature thermistors with a wide temperature range.

Microstructure and dielectric properties of high-entropy Sr0.9La0.1MeO3 (Me: Zr, Sn, Ti, Hf, Mn, Nb) perovskite ceramics

Entropy engineering has attracted extensive attention, which is applied to induce controllable changes in structures through lattice distortion effects to optimize certain properties. In this work, a series of pure phase high-entropy dielectric ceramics, Sr0.9La0.1MeO3 (Me = Zr, Sn, Ti, Hf, Mn, Nb) were synthesized at the sintering temperature of 1550 °C via a traditional solid phase method. The internal relationship between phase stability and dielectric properties with respect to the variation of mixing entropy were investigated. The distortion of oxygen octahedron (in-phase and antiphase) and antiparallel cation displacement were produced in Sr0.9La0.1(Zr0.25Sn0.25Ti0.25Hf0.25)O3 (4M) ceramic system after the introduction of four cations into B-site. Finally, 4M ceramic possesses excellent dielectric permittivity frequency stability and dielectric-temperature stability (εr/ε25°C<5% within −100 to 300 °C) with a low dielectric loss (<0.01). This work provides a valuable reference for entropy engineering to control dielectric performance and phase stability, and may facilitate the discovery and design of novel electronic ceramics.

Experiences and Learnings through Electronic Ceramics Development

Experiences and Learnings through Electronic Ceramics Development

Rainer Waser – A Pioneer of Fundamentals of Resistive Switching Memories

Rainer Waser – A Pioneer of Fundamentals of Resistive Switching Memories

Optimizing the stability and electrical transport properties of CeNbO4+δ-based oxide ceramics by regulating oxygen ion content

CeNbO4+δ ceramics have attracted extensive research interest because of their unique mixed ion-electron transport characteristics and interesting structure-functional characteristics caused by the difference in oxygen ion content. Although the change of oxygen ion content brings rich redox properties, it also causes serious crystal transformation and abnormal electrical transport properties. In order to obtain stable structure and excellent electrical transport properties, the directional regulation of the oxygen ion content has been realized through introducing Al2O3 and high temperature aging. After 600 h of aging at 1073 K, the prepared composite ceramics not only obtain a stable structure without crystal transformation, but also show good negative temperature coefficient (NTC) thermistor characteristics in the temperature range of 473 K–1273 K, in which the linear fitting maximum Pearson's r of the relationship between lnρ and 1000/T can reach 99.97%. The proposed method provides a new thought for the design and application of high-temperature electronic ceramics.

顕微Raman断層イメージングによる電子材料・セラミックス材料研削加工面の品質検査技術

顕微Raman断層イメージングによる電子材料・セラミックス材料研削加工面の品質検査技術

Study on drying kinetics of calcium oxide doped zirconia by microwave-assisted drying

Ca–ZrO2 is an essential structural and functional material, which is commonly used in refractories, electronic ceramics, and functional ceramics. The properties of Ca–ZrO2 materials are depending on the quality of Ca–ZrO2 powders. The main factors affecting the quality of powder are sintering temperature and the drying effect. This paper applied modern microwave drying technology to dry Ca–ZrO2 powder. The impact of initial mass, microwave heating power, and initial moisture content on the drying of Ca–ZrO2 were explored. The results showed that the average drying rate increased with the rise of initial mass, microwave heating power, and initial moisture content. Wang and Singh, Page, and Quadratic Model were applied to fit Ca–ZrO2 with an initial moisture content of 5.6%, mass of 30 g, and microwave output power of 400 W. The results displayed that the Page model had a better fitting effect. It was also applicable to other different initial moisture content, original mass, and microwave heating power. The diffusion coefficient calculated by Fick's second law displayed that with the increase of initial mass, initial moisture content, and microwave heating power of Ca–ZrO2, the effective diffusion coefficient increased first and then declined. When the Ca–ZrO2 of microwave heating power was 640 W, mass was 30 g, and the moisture content was 5.65%, the effective diffusion coefficients of zirconia were 1.42533 × 10−13, 2.91806 × 10−13, 5.652.2471 × 10−13 m2/s, respectively. To determine the activation energy of microwave dried zirconia, using the relationship between microwave power and activation energy, the activation energy of microwave dried zirconia was calculated to be −23.39 g/W. This paper aims to rich experimental data for the industrial application of microwaves to strengthen dried zirconia and propose a theoretical basis.

Development of multifunctional electronic-ceramics with piezoelectric effect and varistor behavior

In this paper, electronic ceramics with multiple functions are studied for the first time and prepared by the traditional solid-phase sintering method. These electronic ceramics were composed by a serious of Pb(Ni1/3Nb2/3)0.55-(ZrxTi1-x)0.45O3 (PNN-PZT) (x = 0.3, 0.285, 0.27 and 0.255) piezoceramics raw materials and the commercial ZnO–Bi2O3 based varistor raw materials. The results show that they exhibit the piezoelectric effect and varistor behavior and that they can produce a kinetic response to a particular critical applied field. The multifunctional ceramics present both piezoelectric effect and varistor behavior simultaneously in a single sample. Two kinds of crystallographic phases in the samples are found, namely, perovskite and wurtzite, based on the XRD, EDS and SEM results. For all multifunctional ceramics, the piezoelectric constants d33 values are over 150 pC/N, potential gradients E1mA values are higher than 1100 V/mm, and nonlinear coefficients α values are over 10. The potential gradient values of multifunctional ceramics are much higher than that of commercially used varistors, and these samples present special hysteresis loops.

Application Status and Development Prospect of Electronic Ceramics

Application Status and Development Prospect of Electronic Ceramics

Original scientific paper examination of influence sintering temperature on mineral compounds

Mineral materials, such as corundum, quartz and periclase are very often used in technological processes. Due to its characteristics, and chemical reaction in solid state, these minerals form very interesting and useful material, cordierite. The mineral ratio in this compound (MgO : Al2O3 : SiO2) is 2:2:5. They form cordierite, electronic ceramic, which can be sintered in a narrow temperature range, at about 1375 °C. Composition of this electronic ceramics material is is 2MgO-2Al2O3-5SiO2 (MAS) and in this research 20% mass Bi2O3 was added in the aim of decrease the sintering temperature. The effects of sintering, the composition and morphology were followed by x-ray diffraction, scanning electron microscopy and EDS analysis, as a function of sintering temperature. MAS ceramics were sintered at 1000ºC, 1100ºC and 1200ºC.

Preface

It was a great pleasure to welcome all the participants from different countries to the 2021 International Conference on Electronic Materials and Information Engineering (EMIE 2021), which was successfully held during April 09-11, 2021 in Xi´an, China. EMIE 2021 provides an enabling platform for Electronic Materials and Information Engineering experts to exchange new ideas and present research results. This conference also promotes the establishing of business or research relations among global partners for future collaboration. We hope that this conference could make significant contribution to the update of knowledge about these latest scientific field.The conference model was divided into two sessions, including oral presentations and keynote speeches. In the first part, some scholars, whose submissions were selected as the excellent papers, were given 15 minutes to perform their oral presentations one by one. Then in the second part, keynote speakers were each allocated 30-45 minutes to hold their speeches. In this conference, we were greatly honored to have invited Professor Alex Lugovskoy from Department of Chemical Engineering, Ariel University as our Conference Chair. There were over 70 experts and scholars in the area of Electronic Materials and Information Engineering representing different famous universities and institutes around the globe to attend the conference.During the conference, we were pleased to invite four distinguished experts to present their insightful speeches. Prof. Fanian Shi, our first keynote speaker, from Shenyang University of Technology. His research interests: Crystal Structure Design and Elucidation; Electromagnetic wave absorbing material; Composite. Prof.Jing Guo, from School of Materials Science and Engineering, Xi’an Jiaotong University. He devoted to electronic ceramics, low temperature sintering, microwave dielectric materials and other related research area. Prof.Yang Yue, from Nankai University. He had outstanding research in intelligent photonics, optical communications and networking, optical interconnect, detection, imaging and display technology, integrated photonics, free-space and fiber optics and other related area. Prof. Xiaoming Zhang, our finale keynote speaker, from Hebei University of Technology. His research area: Topological theory; Electronic materials; 2D materials.The participants of the conference were from most part of the world, with background of either academia or industry, even well-known enterprise. The success and prosperity of the conference is reflected high level of the papers received. The proceedings are a compilation of the accepted papers and represent an interesting outcome of the conference. EMIE 2021 for exchange of research findings, analysis, information, and knowledge in areas which include but are not limited to: Electronic Materials, Information Engineering and other related topics.We would like to acknowledge all of those who supported EMIE 2021. Each individual and institutional help are very important for the success of this conference. Especially we would like to thank the organizing committee for their valuable advices in the organization and helpful peer review of the papers. We sincerely hope that EMIE 2021 will be a forum for excellent discussions that will put forward new ideas and promote collaborative researches. We are sure that the proceedings will serve as an important research source of references and the knowledge, which will lead to not only scientific and engineering progress but also other new products and processes.The Organizing Committee of EMIE 2021List of Committee member are available in this pdf.

Energy storage performance of BaTiO3-based relaxor ferroelectric ceramics prepared through a two-step process

As the industrial pillar of electronic ceramics, BaTiO3 ceramic is difficult to achieve large energy storing performance due to its high Pr and low dielectric breakdown field strength, making it difficult to satisfy their development requirements of miniaturization and lightweight of power electronic equipment. Therefore, a two-step strategy including adjusting the ratio of chemical elements to modify the microstructures and optimizing the preparation process to enhance electric breakdown strength has been proposed to greatly enhance the energy storing performance of lead-free ferroelectric ceramics, whose effectiveness has been proved within this investigation. Especially, the (Ba0.65Sr0.245Bi0.07)0.99Nd0.01TiO3 (BT-SBT-NdVPP) ceramic prepared by this strategy obtains a superhigh energy storage density of 4.2 J/cm3 under 460 kV/cm, and its temperature (30 ~ 100 °C) and frequency (10 ~ 400 Hz) stabilities under 300 kV/cm are pretty good. In addition, this ceramic has excellent pulse performance under 350 kV/cm between 30 and 150 °C. Therefore, this two-step strategy put forward within this investigation not only significantly improves the energy storage performance of BT-based ceramics but also provides a reference for the preparation of dielectric ceramics with high quality, which could has great potential for the practical industrial application.

Electrochemically manipulating BiFeO3 particles via Bi3+ ion extraction

AbstractBecause multifunctional ceramics are widely used in the electronics, manipulating composition and structure of the electronic ceramics aim at improving the performance of the target material for appropriate applications. However, the composite materials with multiphases and multicomponents could be achieved by mixing the nanomaterials with various preparing methods or technologies, which generally require a bunch of experimental design to obtain the target products. For achieving the goals, a novel electrochemical approach for preparing functional ceramic materials is demonstrated via ion extraction from the A site of perovskite BiFeO3 (BFO) ceramic particles, and whereby a single‐phase perovskite BFO could be evolved into multiphase and multicrystalline homogeneous composites. With gradual changes in material particle size, composition, structure, and morphology upon electrochemical Bi3+ ion extraction, the magnetic and electromagnetic properties of the decomposed BFO along with the generated multiphase and multicrystalline composites would present pronounced evolutionary behaviors, compared with original BFO. Apparently, such titration method upon electrochemical ion extraction could be employed to manipulate the properties of the functional ceramics. The simple strategy of electrochemical manipulation BFO would be applied to certain materials with electrochemical activity to achieve the target performance.

Influence of Annealing Atmosphere on Varistor Property of TiO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;-Nb&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O&amp;lt;sub&amp;gt;5&amp;lt;/sub&amp;gt;-SrCO&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt; Ceramics

Varistor ceramics are typical electronic ceramics, which are widely used in circuits of overvoltage protection, high voltage stabilization and high energy surge absorption. TiO2 varistor ceramics has the advantages of low varistor voltage and good dielectric properties, but their low nonlinearity limited the application. The influence of annealing on the varistor properties of TiO2-Nb2O5-SrCO3 ceramics was investigated in this paper. TiO2-Nb2O5-SrCO3 varistor ceramics were prepared by the traditional method of ball grinding-forming-sintering and they were annealed in oxygen and nitrogen, respectively. The nonlinear coefficient α and the breakdown voltage EB of the samples were tested using the varistor dc parameter meter. The microstructure of samples was analyzed by XRD, SEM, STEM-EDAX and SAEDP. The results show that during annealing, Sr2+ ions with a larger radius obtain the kinetic energy and are segregated to grain boundaries, which increases the acceptor density of the grain boundaries and improves α. Annealing in an oxygen atmosphere, the enrichment of oxygen at grain boundaries is also helpful to increase the density of acceptor states and the height of the potential barrier, so as to further increase α. Meanwhile, annealing makes crystalline grains grow properly, which results in even grain size, reduces the porosity and increases the density of grains. So EB tends to reduce. As the doping concentration of Nb2O5 and SrCO3 is 0.15 mol%, respectively, and sintering temperature is 1300°C, TiO2-Nb2O5-SrCO3 varistor ceramics annealed in oxygen for 3 h at 750°C achieved the highest nonlinear coefficient α = 8.9 and the lowest breakdown voltage EB = 19.1 V·mm-1, which annealed in nitrogen achieved α = 8.4, EB = 20.6 V·mm-1, both superior to unannealed samples.

Multi-scale micro-stereolithography using optical fibers with a photocurable ceramic slurry

In this study, ceramic lattice microstructures were fabricated via micro-stereolithography using optical fibers to irradiate a photocurable ceramic slurry containing β-tricalciumphosphate microparticles. Changing the optical fiber core diameter and incident laser power can produce microstructures of the desired linewidths and cured depths. Fabrication conditions, such as scanning distance, accumulation pitch, and number of lamination layers, were optimized using the proposed method. The fabricated lattice structures were degreased and sintered to produce ceramic lattice structures. Overall, a simple and compact fabrication system was proposed for producing 3D microparts fabricated from various kinds of ceramics for electronics, mechanics, optics, and medical applications.