The application of doped HfO2 ferroelectric thin films in nonvolatile memory devices becomes popular in condensed matter physics and materials science. Recent studies indicate that La doped HfO2 has excellent ferroelectric properties, and the ferroelectric remanent polarization is 45 μC/cm2 as the maximum value reported. Nd doping is expected to enhance the ferroelectric properties of HfO2 due to its similar chemical properties of Nd and La, but little research has been reported. In this paper, high quality Nd-doped HfO2 (i.e., Nd:HfO2) thin films were grown on La0.67Sr0.33MnO3 (bottom electrode)/SrTiO3 (001) substrates by using oxide molecular beam epitaxy. According to the results by X-ray diffraction and high-resolution electron microscopy, Nd doping can induce the transition of HfO2 from a monoclinic phase to an orthorhombic phase. In addition, the results by high resolution electron microscopy also show that Nd:HfO2 has a tetragonal phase structure near the interface, connecting (111) crystalline Nd:HfO2 and (001) crystalline perovskite oxide substrates. The systematic studies on epitaxial growth and ferroelectric properties of Nd:HfO2 films can expand the research of doped HfO2.

Ferroelectric materials with a morphotropic phase boundary (MPB) can exhibit enhanced dielectric, piezoelectric, and electrooptic properties, compared with conventional ferroelectric materials. In this paper, dense (1-x)Ba2NaNb5O15-x Sr2KNb5O15 (BNN-SKN) tungsten bronze structured ceramics of binary solid solution system were obtained by a solid-state sintering method. The microstructure and electric properties of BNN-SKN were investigated to explore the potential MPB regions. The MPB coexisting with Ccm2 and P4bm appears as x=0.7. As the SKN content increases, the phase transition temperature and dielectric constant of the measured samples reach their extreme values as x=0.7, i.e., Tm =170, eTR =1 211, and em=3 326. In addition, the ferroelectric properties of BNN-SKN system were also analyzed, and the factors affecting the ferroelectric change in this binary system were discussed.

In our natural environment, mechanical energy has the advantages of universality, diversity, no pollution and easy collection, and occupies a place in various forms of energy. The use of piezoelectric nanogenerators to collect this mechanical energy can provide a feasible solution for the power supply of intelligent functional electronic devices. A BaTiO3/PDMS and BaTiO3/PDMS/C based composite nanogenerator was prepared with lead-free barium titanate (BaTiO3) nanoparticles, carbon nanotubes, and polydimethylsiloxane (PDMS). The results show that the output signal of BaTiO3/PDMS based composite nanogenerator firstly increases, and then decreases with increasing BaTiO3 content. The optimal output signal is obtained at BaTiO3 content of 12%, and the output current and output voltage are 42 nA and 18 V, respectively. The output signal of BaTiO3/PDMS based composite nanogenerator is further improved with introducing C nanotubes. The BaTiO3/PDMS/C based piezoelectric nanogenerator has the optimal output signal when the content of C nanotubes is 2%, and the output current and output voltage are 73 nA and 19 V, respectively. The results indicate that BaTiO3/PDMS/C based piezoelectric nanogenerator has a great application potential in self-powered microelectronic wearable devices.

The effect of Er2O3 doping on the microstructure and electrical properties of ZnO-Bi2O3-Sb2O3-Co2O3-MnO2-Cr2O3-SiO2 varistor was investigated. A part of Er is dissolved in the Bi-rich phase as doping Er2O3, which has a great influence on the grain boundary characteristics and electrical properties of ZnO varistors. The grain boundary resistivity decreases, the leakage current density increases, the double Schottky grain boundary barrier height and the nonlinear coefficient firstly increase and then decrease, and the breakdown field strength increases with increasing Er2O3 content from 0.09% to 0.35% (in mass fraction). The ZnO varistors obtained have a nonlinear coefficient of 54.4±1.5, a breakdown field strength of (470.1±2.8) V·mm-1, a leakage current density of (1.9±0.1) μA·cm-2, and a loss tangent of less than 0.03 at Er2O3 doping content of 0.27%, showing the optimum comprehensive electrical properties. The standard deviation of the performance parameters is small, indicating that the samples have a good reproducibility. This work provides a reference for the preparation of Er2O3-doped ZnO varistor ceramics with the excellent performance.

Cold sintering process (CSP) is an efficient and energy saving sintering method emerging in recent years. In this paper, the (1-x)BNT-xNN dielectric ceramics with the density of more than 97% were prepared by CSP. The effect of CSP parameters and NaNbO3 content on the density, phase structure, microstructure, and dielectric characteristics of (1-x)BNT-xNN ceramics were investigated. The results show that the CSP can drastically reduce the grain size and prevent some components like Bi and Na from volatilizing due to low sintering temperature and short holding time, thereby increasing the dielectric constant and reducing the dielectric loss. The remnant polarization decreases, and the temperature stability of dielectric constant increases as the content of NaNbO3 increases. When x=0.3, the variation in dielectric constant of the 0.7BNT-0.3NN ceramic is less than 6% at 25?傆b400 ℃, and the dielectric loss is less than 5%. It is indicated that the (1-x)BNT-xNN ceramics prepared by CSP are one of the promising candidates for the applications in temperature-stability ceramic capacitors.

Flash sintering is extensively investigated for over a decade since its discovery, but its practical application is seldomly discussed. A primary challenge in utilizing flash sintering is a difficulty in sintering large samples. This is since in a typical direct current (DC) flash sintering, the current is concentrated primarily in the center of the sample, causing a significant temperature gradient between the interior and surface of the sample, thus leading to an inhomogeneous microstructure in the final product and sometimes large stresses in the sample that breaks the material. In this paper, we utilized the alternating current (AC) with varying frequencies to investigate its effect on this inhomogeneity issue in flash sintering. The results indicate that increasing the frequency significantly enhances the uniformity of the sample. The underlying mechanism is related to a significant “skin effect” in AC flash sintering, where the current density is concentrated on the surface of the sample rather than its center, compensating for a higher radiation heat loss at the surface and resulting in a more uniform sample temperature. This work provides a potential approach to enhance the flash sintering for industrial applications.

Y-doped BaZrO3 proton conductor has been extensively studied due to its outstanding chemical stability. However, the high sintering temperature has limited its practical application. To enhance the sintering activity of BaZrO3, we co-doped Y-BaZrO3 with Pr3+ and Ni2+, and investigated its microscopic morphology and electrochemical properties. The introduction of Ni forms a solid solution with the sample, while Pr3+ doping increases the grain size, a critical factor for the densification process. XPS, Raman and EPR results reveal that a small amount of Pr3+ doping significantly raises the concentration of oxygen vacancies in the materials. This increase promotes proton incorporation by accelerating the dissociation and adsorption of water, thereby facilitating the proton conduction. However, it’s important to note that excessive Pr3+ doping leads to a high concentration of oxygen vacancies, which triggers a defect association reaction. Consequently, this results in a slight decrease in conductivity at low temperatures. On the other hand, as the temperature increases, the hydrogen permeability of the membrane increases also rises. Moreover, the hydrogen permeability of BaZr0.66Y0.2Pr0.1Ni0.04O3-δ is found to be higher than that of BaZr0.71Y0.2Pr0.05Ni0.04O3-δ, with the former reaching 2.60×10-8 mol·cm-2·s-1 at 1 173 K. Notably, these membranes exhibit remarkable in CO2-containing atmosphere indicating excellent resistance to CO2.

As one of emerging ceramic materials, high-entropy ceramics become a research hotspot in the field of ceramics. However, their compositional design has some challenges for component design based on experimentation and “trial and error”. In recent years, the combination of machine learning and experiments can provide an effective method to solve this problem. In this paper, four machine learning models were established, the best-performing gradient-boosting decision tree model (R2=0.92) through training and evaluation was selected for prediction. A single-phase (Ti0.2V0.2Zr0.2Nb0.2Hf0.2)N high-entropy nitride ceramic was then synthesized based on the predication by the model. This effective approach can provide some ideas for the design of high-entropy nitride ceramic and discover new systems.

Single-phase bulk high-entropy spinel ceramics of (Mg0.2Co0.2Ni0.2Cu0.2Zn0.2)Fe2O4 were prepared via solid-phase reaction. The phase composition, microstructure and element distribution were analyzed by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The volume density of the ceramics increases and the porosity decreases with the increase of sintering temperature. The dense high-entropy spinel ceramic sintered at 1 200 ℃ presents a single-phase, uniform distribution of elements, and its bending strength and fracture toughness reach 43.00 MPa and 1.30 MPa·m1/2, respectively. The high-entropy spinel ceramic as a good load bearable broadband microwave absorbing ceramic has dielectric loss and magnetic loss to electromagnetic wave, and the maximum effective absorption bandwidth (EAB=12.37 GHz) maxi can be obtained at 3.0 mm.

The macroscopic mechanical response and micro-fracture mechanism of Al2O3/SiC composite as a multiphase ceramic under impact loading were investigated. The dynamic strength and strain rate sensitivity were analyzed by load tests methods of one-dimensional stress wave and plane shock wave. The Hugoniot curve of high pressure and local deformation characteristics of material were determined at different stress modes. The results show that the micro-fracture mechanism of the multiphase ceramic differs with the macro-stress characteristics. The macro-deformation of the multiphase ceramic is mainly a brittle failure under impact loading. However, there are some local plastic deformation characteristics on the transcrystalline fracture of large grain and the intergranular fracture of small grain. The SiC particles as a second phase induce crack propagation at grain boundaries and within grains, which plays an important role in the redistribution of impact energy.

Al-pillared montmorillonite/carbon nanocomposites were prepared by a hydrothermal method using Al-pillared montmorillonite as a template and chitosan as a carbon source, and then hot-pressed to obtain Al-pillared montmorillonite-based ceramic/carbon composites. The effect of carbon content on the densities, mechanics, electrical conductivity and wave absorption properties of the composites was investigated by X-ray diffraction, scanning electron microscopy, universal material tests and vector network analysis. The results show that the Al-pillared montmorillonite/carbon is transformed into mullite/carbon ceramic material by hot-press sintering, and the carbon is further graphitized in the hot pressing. The introduction of carbon enhances the electrical conductivity and toughness of the composites, while a large amount of interfacial polarization is formed inside the material, which enhances the dielectric loss of the composites and transforms the ceramic material from a wave-transparent body to an electromagnetic wave absorbing material. The internal microcracks of the composites increase and the flexural strength gradually decreases with the further increase of carbon mass fraction in aluminum column-supported montmorillonite. The fracture toughness of the composite material is the maximum value when the mass ratio of montmorillonite to chitosan is 32 at 1 300 ℃, 20 MPa and 120 min of holding time, which is 11.41% greater than that of ceramics without carbon addition. The maximum electrical conductivity of the composite material is 17.53 S·m-1 when the mass ratio of montmorillonite to chitosan is 4. According to the simulation calculations through wave absorption performance tests, the minimum RL value of the obtained material reaches -44.93 dB when the coating thickness is 1.4 mm. The minimum RL value is -36.28 dB and the effective absorption bandwidth is 5.0 GHz when the coating thickness is 1.6 mm.

Novel high-temperature thermal barrier materials become the key materials for the development of new generation aeroengines. In this paper, a monoclinic high-entropy rare-earth tantalate material (Y0.2Gd0.2Dy0.2Ce0.2La0.2)TaO4[(5RE0.2)TaO4] was synthesized via solid-state reaction. The thermal, the mechanical and the molten silicate environmental deposits (CMAS) corrosion resistance were investigated. The results indicate that (5RE0.2)TaO4 exhibits a low thermal conductivity (i.e., 1.22 W·m-1·K-1, 600 ℃) and a high thermal expansion coefficient (i.e., 10.3×10-6 K-1，1 200 ℃), Compared with YSZ material (i.e., 2.1-2.7 W·m-1·K-1，100-900 ℃), the thermal conductivity is decreased by 42%. The fracture toughness reaches 2.8 MPa·m1/2, which is superior to most thermal barrier coating materials because of its unique ferroelastic toughening effect. The thickness and penetration depth of the (5RE0.2)TaO4 reaction layer are smaller than those of the YSZ material after being corroded by CMAS at 1 350 ℃ for different durations. This material is a developed thermal barrier coating material with a great application potential.

A textured SiAlON ceramic with a centripetal grain alignment was obtained via sinter-forging through outer diameter strain ring compression using spark plasma heating. The microstructure, texturing degree and anisotropy of mechanical properties of the ceramic were investigated. The results show that the c-axis (i.e., long axis) of the rod-like SiAlON grains is parallel to the radial direction of the cylindrical sample, forming a centripetal grain alignment. The average included angle between the c-axis and radial direction is 19.2° and 9.9° on the plane perpendicular to pressing direction and parallel to radial direction, respectively. The degree of centripetal texture is 0.79. The hardness on the plane perpendicular to pressing direction is 12% greater than that on the plane perpendicular to radial section, reaching 17.85 GPa. The flexural strength with fracture plane perpendicular to radial section is 57% greater than that with fracture direction parallel to radial direction, which is 1 341 MPa. The fracture toughness with crack propagation perpendicular to radial section is 75% higher than that with crack direction parallel to radial direction, which is 6.27 MPa·m1/2.

Direct ink writing technology is conducive to molding personalized and customized products with complex structures. However, it is easy to produce pores and an-isotropic problems of mechanical properties when printing a dense solid structure. In this paper, Al2O3 was used as a raw material and a nozzle with a diameter of 2.0 mm was selected for direct ink writing. The results show that the layer height is 0.8 mm, the internal structure of the printed sample is relatively dense, and no pores appear after writing. Also, the mechanical properties parallel to/perpendicular to the inter-layer are similar, and the anisotropy index is close to 100%, thus alleviating the anisotropy problem of mechanical properties.

Silicon carbide (SiC) ceramic has a broad application prospect in aerospace and nuclear power industries due to its advantages of high strength, high hardness and low density. However, the processing difficulty and low toughness of SiC hinder its application. To solve the problems above, SiCw/SiC composites containing different silicon carbide whiskers (SiCw) were prepared via binder jetting additive manufacturing and liquid silicon infiltration. The experimental results show that the flexural strength and fracture toughness of the composite can be 215.29 MPa and 3.25 MPa·m1/2 when SiCw contentis 7.5% (in volume fraction), and the hardness is 23.06 HV at 5% SiCw. However, the residual silicon phase content within the composite elevates, and the mechanical properties deteriorates when SiCw content further increases. The two carbonization processes to the green parts effectively reduce Si phase content and increase the flexural strength, fracture toughness, and hardness by 10.15%, 10.46%, and 10.58%, respectively. SiCw is added as a reinforcing and toughening agent for the composite ceramic via deflection cracking, pulling out and fracturing.

Achieving a biocompatible joint between titanium alloy and ZrO2 ceramic is of great significance to extend its application in the biomedical field. In this paper, the joining between Ti-13Nb-13Zr alloy and ZrO2 ceramics was achieved with Sn-Zr filler metal. The interfacial microstructure and reaction products of TNZ/ZrO2 joints were analyzed by X-ray diffraction, scanning electron microscopy and energy disperse spectroscopy, and the shear test was carried out to evaluate the mechanical properties of joints. The effect of Zr content on the interfacial microstructure and mechanical properties of the joints was also investigated. The results show that the typical microstructure of the joints brazed at 600 ℃ for 30 min with Sn-6Zr (atomic fraction) filler metal is TNZ/Ti6Sn5/β-Sn+Zr(s,s)+ ZrSn2/m-ZrO2/ZrO2. Among all of the reaction phases, the formation of m-ZrO2 facilitates the metallurgical bonding between ZrO2 substrate and brazing seam. The amounts of both Zr solid solution and ZrSn2 phase increase, but the proportion of β-Sn in the brazing seam gradually decreases with the increase of Zr content. The maximum average shear strength of brazing joints reaches 25.6 MPa when the Zr content is 6%. According to the analysis of fracture path, the joints brazed with Sn-6Zr mainly fracture along the β-Sn in the brazing seam.

(Ni, Sb)-codoped rutile yellow (NiSb-RTi) pigment with a high near-infrared (Near infrared, NIR) reflectance was prepared by a solid-phase method, and then (Ni, Sb)-codoped rutile/silica aerogel (NiSb-RTi/silica aerogel) hybrid pigment with a high NIR reflectance and a network structure was prepared with SiO2 aerogel substrate. The structural characteristics, color rendering performance, NIR reflectance, and thermal insulation performance of the hybrid pigment were characterized. The results show that NiSb-RTi pigment synthesized at 1% (in mass fraction) NaF as a sintering aid has superior color rendering performance (b*=54.24) and NIR reflectance. NiSb-RTi/silica aerogel hybrid pigment with a network structure has a good color rendering performance, a low transmittance, a high NIR reflectance (i.e., 96.60%) and a low thermal conductivity (i.e., 0.068 54 W/(m·K)), indicating a superior thermal insulation performance. In addition, the preparation process and thermal insulation mechanism of the hybrid pigment with a network structure were also discussed.

The blue and cyan amorphous photonic color glazes were prepared with the addition of 2%-7% niobium pentoxide to Na2O-K2O-MgO-CaO-Al2O3-SiO2 ceramic glaze. The effect of Nb2O5 addition on the glaze color, phase-separated structure and elemental distribution was investigated by UV-Vis reflection spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscope, transmission electron microscope, and the regulation mechanism on the structural color of amorphous photonic was analyzed. The results indicate that the [NbO4] tetrahedra transforms into [NbO6] octahedra as the content of Nb2O5 increases, which exists as network oxides, causing a decreased viscosity of the glaze melt at high temperatures and an increased size of the phase-separated droplets. Also, a large enrichment of Nb2O5 improves the refractive index difference between the two phases, leading to the wavelength of amorphous photonic structural coloration moving to the long-wave direction and a transition of the glaze color from blue to cyan.

The Al2O3-ZrO2-Cr2O3-SiO2 (AZCS) material as a new type of fused-cast refractory has better corrosion resistance than other fused refractories under high-temperature and high-corrosion resistance conditions. To investigate the erosion resistance behavior of the material to the borosilicate glass melt, the AZCS material was subjected to an erosion test at 1 500 ℃, by using borosilicate glass waste-forms containing B2O3 of 12% (in mass fraction). The samples before and after erosion were analyzed by chemical analysis, X-ray diffraction, scanning electron microscopy and energy disperse spectroscopy. The results show that AZCS material can be divided into the metamorphic layer, transitional layer and central layer based on the degree of corrosion. The central layer changes little, there are still a large amount of aluminum-chromium solid solution and baddeleyite, and only a small amount of newly formed magnesia-alumina spinel. MgO infiltrating the material reacts with the solid solution to form the MA spinel in situ and partially replaces the aluminum-chromium solid solution in the original position. In the transitional layer, the maximum amount of MA spinel is formed, and the Al-Cr solid solution dissolves and disappears. Therefore, the phases in this layer are MA spinel and baddeleyite. In the metamorphic layer, there is basically only undissolved Cr2O3 phase with a loose Cr2O3 structure and a worm-like morphology. Aluminum-chromium solid solution, baddeleyite and MA spinel dissolve and disappear.

Microwave absorbing materials refer to a class of materials that can absorb or weaken the electromagnetic wave energy on their surface, thereby reducing electromagnetic interference. In recent years, various high-entropy ceramic absorbing materials have emerged in the exploration of absorbing materials. These materials exhibit a better absorbing performance than single-component materials due to their thermodynamic high-entropy effect, lattice distortion effect in structure, hysteresis diffusion effect in kinetics, and synergistic enhancement effect of components. This review summarized recent research results on the component design, preparation, and absorbing performance relationship of different types of high-entropy absorbing ceramics, and analyzed the influence of high-entropy effect on its absorbing performance. In addition, this review also summarized the corresponding scientific issues and challenges in research work and prospected the future development directions of high-entropy absorbing ceramics.

The emission of electromagnetic wave is a fundamental property of any substance at a temperature higher than 0 K. However, the capability of thermal radiation is not an immutable property of materials, and the static and dynamic modulations of thermal emission are realized by different methods in recent years. This review represented the general principles of thermal emission, and recent work on the static and dynamic modulation of infrared thermal emission by using nanophotonic structures. Besides, the emerging applications of spectrally modulated selective infrared emitters in fields such as energy were highlighted. In addition, this review also summarizedthe current problems and outlined the potential future direction in the modulation of infrared emission of inorganic materials.

In the field of backlight liquid crystal display (LCD), narrow-band green-emitting phosphor plays an important role in expanding the color gamut, improving luminous intensity and optimizing color rendering performance. This review represented recent research progress on the narrow-band green emission phosphors. The phosphors classified by different activating ions, i.e., Eu2+ and Mn2+, were introduced, and the relationships between their structures and luminescence properties were analyzed. In addition, the advantages and disadvantages were described and the future development were also prospected.