ABSTRACT A process for developing statistically relevant mechanical properties of advanced, high‐value ceramics using smaller, miniaturized, specimen volumes is crucial due to the challenges associated with the manufacturing and cost challenges associated with larger samples. In this study, a miniaturized ball‐on‐3‐ball (B3B) method was designed to determine the transverse rupture strength (TRS) of miniaturized right‐cylindrical technical ceramics. Two fixture configurations were tested and compared, and an optimal fixture design is demonstrated. Three technical ceramics were tested to validate the miniaturized B3B fixture, including commercially available alumina (Al 2 O 3 ), magnesia partially stabilized zirconia (MSZ), and yttria partially stabilized zirconia (YSZ). A statistically relevant number of samples ( N > 59) for each material were tested to allow for an accurate Weibull statistics assessment. TRS testing of Al 2 O 3 , MSZ, and YSZ resulted in characteristic strengths of 437, 1168, and 1380 MPa, respectively. Weibull moduli of Al 2 O 3 and MSZ were both determined to be nearly 12, whereas the Weibull modulus of YSZ was determined to be 7. The TRS and Weibull data for Al 2 O 3 , MSZ, and YSZ obtained in this study yielded comparable results to prior results using larger‐volume samples. Grain morphology was quantified via electron microscopy.
ABSTRACT Porous ceramic cores are widely used in high‐temperature filtration, catalytic carriers, aerospace, and precision casting due to their lightweight, high specific surface area, and excellent thermal stability. However, achieving a balance between high porosity and mechanical strength remains a key challenge. In this study, modified aramid fiber microspheres (20 µm) were introduced as pore‐forming agents into a photocurable alumina slurry, and the sintering process was optimized to achieve isotropic shrinkage. After systematically evaluating printing orientation, pore‐forming agent content, and sintering temperature, the optimal scheme was determined: horizontal printing with 9% pore‐forming agent, followed by sintering at 1600°C. The resulting alumina ceramic core exhibited high porosity (32.48 ± 0.31%), high flexural strength (20.51 ± 0.93 MPa), and excellent surface accuracy (Ra = 6.46 ± 0.40 µm). Furthermore, finite element simulations clarified the influence of pore structure on mechanical performance. This study achieved an effective balance between porosity and mechanical strength in 3D printed alumina ceramics, providing a new method for fabricating lightweight, thermally stable ceramic cores with tunable pore structures.
ABSTRACT Aluminum nitride (AlN) ceramic substrates are essential for advanced electronics due to their high thermal conductivity and electrical insulation. However, tape‐casting fabrication of dense, high‐thermal‐conductive AlN substrates is often hindered by difficulties in preparing high‐solid‐loading, low‐viscosity, and stable slurries. This study optimized rheological and antisedimentation behaviors by adjusting additive compositions (dispersant, binder, plasticizer) of the tape‐casting AlN slurries. A ternary dispersant system (glycerol trioleate/castor oil/KH560 at a mass ratio of 2:2:2 wt.%) enhanced the rheology and stability of AlN slurry through synergistic chemical anchoring, physical adsorption, and steric hindrance, reducing agglomeration. Optimizing the binder‐to‐plasticizer ratio further improved slurry rheology and stability, as well as enhanced the flexibility, strength, and surface quality of AlN green tapes. Using this approach, slurries with AlN solid loadings of 64–68 wt.% were produced and cast into uniform green tapes, then sintered into dense ceramics. The slurry with 68 wt.% AlN solid loading yielded a substrate with a bulk density of 3.25 g·cm − 3 , apparent porosity of 1.02%, and thermal conductivity of 176.14 W·m − 1 ·K − 1 . These results demonstrate a clear correlation between formulation of AlN slurry and tape‐casting ceramic performance, offering a practical guideline for manufacturing high‐performance ceramic substrates for next‐generation electronics.
ABSTRACT Piezoelectric materials are essential functional components widely employed across diverse technological fields. With increasing demands from aerospace, nuclear, and other extreme‐environment industries, the development of piezoelectric materials capable of reliable operation at elevated temperatures has become a critical research focus. Bismuth titanate (Bi 4 Ti 3 O 12 , BIT), an Aurivillius‐type layered ferroelectric, has emerged as a leading candidate for high‐temperature piezoelectric applications owing to its high Curie temperature (∼675°C) and large spontaneous polarization (∼50 µC/cm 2 ). This review comprehensively examines the crystal structure and electrical properties of BIT and systematically summarizes key strategies for enhancing its performance, including optimization of fabrication processes, composition control (A‐site, B‐site, and co‑substitution), microstructure tailoring (grain size and grain orientation engineering), and the design of intergrowth structures. Furthermore, recent advances in high‑temperature piezoelectric devices based on BIT, such as ultrasonic transducers and composite materials, are discussed. The paper also addresses persistent challenges, such as limited densification, insufficient piezoelectric response, and dielectric losses, and proposes potential solutions. This work aims to provide a valuable reference for the design and application of BIT‑based materials in next‑generation high‑temperature piezoelectric systems.
ABSTRACT The preparation of magnesium aluminate (MgAl 2 O 4 ) spinel refractory aggregates was undertaken using local Indian magnesite and bauxite through a simple one‐step solid‐state sintering method with a view to investigating the effect of stoichiometry on the properties of the material. Stoichiometric composition has Al 2 O 3 :MgO compositions of 1:1 where as the non‐stoichiometric mixes have two variations with MgO rich and Al 2 O 3 rich. These were produced and subsequently sintered at temperatures between 1450°C and 1600°C. The relationship between phase formation, microstructure and properties was investigated through XRD, FE‐SEM, and EDS analyses, whereas density, porosity, shrinkage, and cold crushing strength were measured for the determination of the refractory characteristics of the material. The optimum densification to stoichiometric composition at 1500°C gave a density of 3.34 g/cc (about 93% of theoretical) and improved mechanical properties due to the presence of impurity oxides in the raw materials that acted as liquid‐phase formers during sintering.
ABSTRACT Bi‐based lead‐free dielectric materials have emerged as a promising materials platform for pulsed power capacitors owing to their high polarization potential, rich local structural diversity, and broad tunability across multiple length scales. The 6s 2 lone pair electrons of Bi 3+ favor large polar displacements, while cation disorder, local structural distortion, and phase competition promote the formation of nanodomains, polar nanoregions, and relaxor states. These characteristics provide a structural basis for achieving low remanent polarization and reversible energy‐storage behavior. However, their practical performance is often limited by Bi volatilization, oxygen vacancies, and defect‐assisted conduction, which degrade breakdown strength, efficiency, and reliability. This review summarizes recent progress in four representative Bi‐based systems: BiFeO 3 ‐based materials, BNT‐based materials, BMT‐related BiMeO 3 systems, and Aurivillius‐type layered compounds. We highlight how each system addresses the key trade‐off between high polarization and high insulation with low hysteresis. We further discuss major optimization strategies, including compositional engineering, high‐entropy engineering, defect and bandgap engineering, nanodomain and local structure engineering, grain and densification engineering, and interface and heterostructure engineering. Finally, future opportunities are discussed for application‐oriented development in low‐/medium‐field, high‐temperature, multilayer, and thin‐film capacitors.
ABSTRACT In this study, aiming to achieve high‐temperature stability alongside a high piezoelectric coefficient, a series of Na 0 . 5 Bi 4 . 5 Ti 3 . 94‐x Mn 0 . 06 Nb x O 15 bismuth‐layered piezoelectric ceramics were prepared and poled under an applied electric field of 12 kV/mm to activate nanodomains within the ceramic and induce their orientation. Comprehensive analysis revealed that the incorporation of Nb 5 + ions into the B‑site of the lattice resulted in a reduction of ferroelectric domain size and an increase in ferroelectric domain density. Consequently, the electrical properties of the Na 0 . 5 Bi 4 . 5 Ti 3 . 94‐x Mn 0 . 06 Nb x O 15 ceramics were significantly improved. Notably, the composition with x = 0.04 exhibited a particularly high piezoelectric coefficient ( d 33 ) of 40 pC·N − 1 and a high Curie temperature ( T C ) of 671.3°C. Furthermore, this composition demonstrated excellent thermal stability, maintaining d 33 above 30 pC·N − 1 over a temperature range of 25°C–400°C. These findings not only position this material as a robust candidate for high‑temperature applications but also provide valuable insights into the design of piezoelectric ceramics with enhanced stability and performance.
ABSTRACT Electrical discharge machining (EDM) can fabricate SiC ceramic components with complex shapes and high precision, but pristine SiC is too resistive for EDM. In this study, SiC‐based conductive ceramics were fabricated by pressureless solid‐phase sintering, employing commercially available transition metal borides TiB 2 , NbB 2 , and multi‐walled carbon nanotubes (MWCNTs) as conductive phases. The effects of conductive‐phase content on phase composition, electrical conductivity, and mechanical properties were investigated. The results show that during high‐temperature sintering, SiC undergoes a phase transformation, while TiB 2 and NbB 2 undergo interdiffusion, leading to the formation of a Nb–Ti boride phase indexed as NbTiB 4 by XRD/Rietveld analysis. The electrical results qualitatively suggest that the conductivity enhancement is associated with a reduced contribution from grain‐boundary barriers and progressively improved connectivity of conductive‐phase pathways. The composites reach a minimum resistivity of 0.19 Ω·cm, which is below the commonly cited resistivity criterion for EDM eligibility. Relative to S0, which exhibited a flexural strength of 294.9 ± 14.1 MPa and a fracture toughness of 2.60 ± 0.14 MPa·m 1/2 , the composites achieved maximum values of 539.0 ± 17.1 MPa and 5.67 ± 0.47 MPa·m 1/2 , respectively.
ABSTRACT Due to its enhanced design flexibility, additive manufacturing (AM) is a game‐changing technology for piezoelectric ceramics. Still, to achieve a high‐quality ceramic by AM, slurry preparation is critical. Piezoceramics based on potassium sodium niobate [(K, Na)NbO 3 ] (KNN) are challenging to densify and therefore require extra care during slurry preparation, including adjustments for differences in the starting powder. This work presents slurries for vat photopolymerization (VPP) AM of lead‐free piezoelectric ceramics based on KNN. Powders made of two different synthesis methods, solid‐state synthesis and spray pyrolysis, with different particle morphology and size distribution, were used to formulate highly loaded non‐aqueous slurries. The rheological properties were highly dependent on powder characteristics, but suitable rheological performance could be achieved for both powders. The densities of the sintered KNN were ∼93%–94%, which is in the range typical for conventionally produced KNN, and all samples show reasonable ferroelectric and piezoelectric response for this material system. These results demonstrate the feasibility of VPP for KNN‐based piezoceramics and provide practical guidelines for slurry design based on powder characteristics.
ABSTRACT Beta‐tricalcium phosphate (β‐TCP) possesses excellent bioresorbability; however, achieving sufficient mechanical strength for load‐bearing applications remains a major challenge. This study aimed to fabricate hydroxyapatite (HA)/β‐tricalcium phosphate (β‐TCP) biphasic calcium phosphate (BCP) consolidated bodies by hydrothermal treatment and to identify factors contributing to strength enhancement. Consolidated β‐TCP bodies were hydrothermally treated at 200°C–290°C and characterized by compressive strength testing, x‐ray diffraction (XRD), scanning electron microscopy, and potentiometric titration. The relationship between the Equi‐Acid‐Base‐Point (EABP) and compressive strength was also examined. Hydrothermal treatment promoted the transformation of β‐TCP to HA with increasing temperature, resulting in a maximum compressive strength of 57 MPa. In contrast, the amount of water used during treatment had little effect on strength. Potentiometric titration revealed that the EABP shifted toward lower pH values with increasing treatment temperature, and this shift correlated with enhanced compressive strength. The observed EABP changes could not be explained solely by HA formation and suggested the formation of calcium phosphate phases with lower Ca/P ratios. These results indicate that strengthening of β‐TCP consolidated bodies is governed not only by β‐TCP‐to‐HA phase transformation but also by compositional and microstructural changes associated with dissolution–reprecipitation.
ABSTRACT Carbon/carbon (C/C) composites are promising high‐temperature structural materials because of their high specific strength, thermal conductivity, and thermal stability. However, severe oxidation above 400°C significantly degrades their performance. Although oxidation‐resistant coatings can effectively protect C/C composites, thermal expansion mismatch between the coatings and the substrates often causes cracking and coating failure. To address this issue, nanotoughening strategies based on coating reinforcement and matrix modification have been extensively developed. Nanomaterials such as silicon carbide (SiC) nanowires, HfC nanowires (HfCNWs), and carbon nanotubes (CNTs) enhance toughness through crack bridging, crack deflection, and interfacial strengthening. This review summarizes recent progress in the application of these nanomaterials to coating toughening and matrix modification of C/C composites, focusing on fabrication methods, toughening mechanisms, and performance improvements. The relationships among reinforcement design, interfacial regulation, and oxidation resistance, thermal shock resistance, and ablation resistance are discussed, providing guidance for the development of advanced ceramic coatings and high‐temperature structural materials.
ABSTRACT Over the past 50 years, the sol–gel process has advanced both scientifically and technologically. In this review, the process as applied to silicates is examined with a focus on its successes and its potential for further implementation. The emphasis is on applications, rather than basic science. At times, the product is identified explicitly as being a sol–gel processed material. In other cases, sol–gel processing is inferred based on the precursors and is one of many steps in producing the product.
ABSTRACT Titanium diboride (TiB 2 ) is a representative ultra‐high‐temperature ceramic; however, its limited sinterability and intrinsic brittleness restrict structural applications. In this study, TiB 2 ‒MoB 2 ceramic composites were fabricated via reactive pressureless sintering at 1550°C to investigate the effects of MoB 2 content on densification behavior, microstructural evolution, and mechanical property trends. A compositional series from TiB 2 ‐rich to Mo‐rich was characterized using XRD, SEM/EDS, X‐ray computed tomography (CT), and mechanical testing. TiB 2 ‐rich ceramics exhibited dense, near single‐phase microstructures with the highest hardness and flexural strength. Increasing MoB 2 content promoted phase segregation, grain‐boundary‐associated porosity, and heterogeneous fracture paths, leading to reduced hardness and strength but progressively enhanced fracture resistance. Fracture toughness increased to values approaching ∼10 MPa·m 1/2 , attributed to increased crack‐path tortuosity, crack deflection, and intragranular fracture at TiB 2 ‒Mo‒boride interfaces. Notably, the intermediate 50TM composition showed the most balanced performance, achieving a relative density of ∼94.7%, a flexural strength of ∼323 MPa, and a fracture toughness of ∼8.9 MPa·m 1/2 . These results demonstrate that controlled MoB 2 incorporation enables systematic tuning of densification and mechanical properties in TiB 2 ‐based refractory ceramics.
ABSTRACT This review aims to critically analyze the fatigue, aging, wear, and interface‐driven performance of contemporary zirconia crown systems and to establish evidence‐based, indication‐specific guidance for clinical material selection. A comprehensive narrative review was conducted focusing on experimental fatigue studies, hydrothermal aging investigations, wear simulations, bonding durability assessments, and long‐term clinical reports of zirconia crowns. Data were synthesized across zirconia systems with differing yttria contents (3Y‐TZP, 4Y‐PSZ, and 5Y‐PSZ) to identify dominant failure mechanisms, quantify performance limits, and evaluate the influence of surface finishing and cementation strategies under simulated oral service conditions. The analysis demonstrates that the long‐term clinical performance of zirconia crowns is governed primarily by fatigue resistance, surface integrity, and interfacial stability, rather than static strength alone. Tetragonal‐rich 3Y‐TZP exhibits superior fatigue reliability and aging resistance, supporting its use in posterior and high‐load conditions. Increased yttria content enhances translucency but reduces fracture toughness, fatigue thresholds, and tolerance to hydrothermal aging, thereby restricting high‐translucency zirconia to low‐stress indications. Polished surfaces significantly reduce antagonist wear, while MDP‐based adhesive cementation improves retention and fatigue performance, particularly in short or minimally retentive preparations. This review provides a clinically performance‐driven synthesis of zirconia crown behavior, integrating mechanical degradation mechanisms with clinical outcomes.
ABSTRACT Zinc aluminate spinel (ZnAl 2 O 4 , gahnite) is gaining importance as a spinel component in the alumina spinel refractory castables due to its excellent thermo‐mechanical and chemical properties. The present work investigates the effect of the amount of in situ formed ZnAl 2 O 4 spinel on the properties of cement‐bonded high‐alumina castable. ZnO was added in the castable composition at 4.4, 6.6, and 8.8 wt.% to form 10, 15, and 20 wt.% in situ ZnAl 2 O 4 spinel, respectively. The castable compositions were processed through conventional technique and heat treated at 110°C, 1000°C, and 1550°C. They were then characterized for various refractory properties, namely, bulk density, apparent porosity, strength at ambient and elevated temperatures, phase analysis, and microstructural study. The optimum ZnAl 2 O 4 ‐containing composition was further characterized for resistance against thermal shock and slag corrosion. The evaluated properties were compared against a high‐alumina castable (without ZnO), used as a reference. The results show that 10 wt.% in situ ZnAl 2 O 4 spinel‐containing castable has the optimum properties. The properties indicate that the Al 2 O 3 ‒ZnAl 2 O 4 spinel castables can substitute Al 2 O 3 ‒MgAl 2 O 4 spinel castables, especially for iron and steel industry applications.
ABSTRACT Zeolite catalysts and adsorbents are widely used in the petrochemical industry, environmental governance, and gas separation, and will play an increasingly important role in emerging technologies such as energy conversion. Customized zeolite design requires an in‐depth understanding of crystallization pathways to accurately manipulate nucleation and growth. Due to the complexity of synthesis media and the diversity of mechanisms, a systematic summary of existing knowledge is essential. This paper reviews representative synthesis strategies—including traditional hydrothermal routes, solvent‐free synthesis, and steam‐assisted crystallization—and investigates the critical factors influencing zeolite formation. We specifically focus on the distinct roles of liquid‐phase, solid‐phase, and solid‐liquid biphasic mechanisms. Furthermore, we analyze the crystallization trends of key framework types, such as LTA, FAU, MFI, and CHA, elucidating the effects of precursor assembly and induction period dynamics. Finally, we propose current research gaps and future directions to advance the precise synthesis of zeolite materials.
ABSTRACT In the present investigation, (TiB 2 –SiC)/B 4 C composite ceramics were successfully prepared through an in situ reaction strategy utilizing SPS, where precisely synthesized controlled additions of 25 wt.% TiSi 2 and carbon powders functioned as effective sintering aids. The processing parameters, specifically sintering temperature (1450°C, 1550°C, 1650°C, and 1750°C) and applied pressure (0, 50, and 80 MPa), were systematically varied under short‐duration holding conditions to elucidate their effects on phase evolution, microstructural development, and resultant mechanical properties. The findings indicate that both sintering temperature and pressure significantly govern the densification kinetics and mechanical response of the composite system. The optimum mechanical properties were attained under specific sintering conditions of 1650°C and 80 MPa, where the composite demonstrated exceptional mechanical characteristics with a Vickers hardness of 33.92 GPa, flexural strength of 546.02 MPa, and fracture toughness of 6.75 MPa·m 1/2 . The enhancement in comprehensive performance is principally ascribed to a reduction in residual porosity, refined grain microstructure, a combination of intergranular and transgranular fracture modes, and synergistic strengthening mechanisms facilitated by the in situ‐formed second phases.
ABSTRACT Bioactive glasses (BGs) have evolved significantly since their discovery in the late 1960s, transitioning from simple biocompatible materials to multifunctional platforms capable of modulating tissue response at the molecular level. BGs can dissolve in physiological environments, precipitate hydroxyapatite, and release therapeutic ions, establishing them as third‐generation biomaterials. Among emerging functionalities, antibacterial properties have attracted considerable interest, driven by the need for materials capable of preventing and combating infections in biomedical applications. Early compositions, such as 45S5 and S53P4, exhibited antibacterial effects mainly via pH changes, whereas more recent formulations incorporate antibacterial ions to achieve stronger and tunable effects. Metallic ions – including silver, copper, zinc, strontium, cerium, and boron – can confer bactericidal activity, acting through membrane disruption, enzyme interference, oxidative stress, or inhibition of DNA replication. Modifying BG compositions allows the creation of materials combining osteogenic and antibacterial functions, enabling applications in bone scaffolds, implant coatings, and wound healing. This review summarizes recent advances in the design, mechanisms, and biological performance of antibacterial BGs, emphasizing translational potential. By integrating findings from in vitro, in vivo, and clinical studies, we highlight the strengths and challenges of BGs that couple regenerative capability with antibacterial action, offering insights for future biomedical development.
ABSTRACT A novel series of high‐entropy ceramics (Y 0.25 La 0.25 Nd 0.25 Eu 0.25 ) 2 (Zr 1‐ x Ti x ) 2 O 7 ( x = 0, 0.25, and 0.5) was synthesized via solid‐state reaction. The results indicated that the doping of Ti 4+ partially substituted the site of Zr 4+ , induced lattice distortion, and tuned thermophysical properties. The thermal conductivity at 25°C reaches its minimum value of 1.233 W·m −1 ·K −1 at x = 0.25, representing a 15% reduction compared to the undoped sample, while maintaining a coefficient of thermal expansion near 10.30 × 10 −6 K −1 . Notably, under the combined effects of grain refinement and stress concentration, the fracture toughness of (Y 0.25 La 0.25 Nd 0.25 Eu 0.25 ) 2 (Zr 1‐ x Ti x ) 2 O 7 ( x = 0.25) increases to the value of 1.746 MPa·m 1/2 , while the elastic modulus decreases to 79.42 GPa. This work demonstrates that the design of B‐site doping can effectively improve the thermophysical properties of rare‐earth zirconates, making these ceramics promising candidates for next‐generation thermal barrier coatings.
ABSTRACT Within the industry of plate‐shaped corundum advanced refractory industry, firing temperatures are concentrated around 1900°C. Due to the interwoven structure of plate‐shaped crystals, the compressive strength of most plate‐shaped corundum exceeds 200 MPa. To reduce energy consumption, this study used γ‐Al 2 O 3 and activated modified limestone fine powder as raw materials. Sintering was conducted at 1600°C, 1650°C, and 1700°C to investigate the effects of modified limestone content and sintering temperature on the phase composition and properties of the composite material. The study revealed that with increasing reaction temperature, the bulk density and compressive strength of the composite phase material first increased and then decreased, while the apparent porosity continuously decreased. When the modified limestone content was 1.11 wt.%, the sintered product at 1650°C achieved a relatively favorable apparent porosity of 13.31%, a bulk density of 3.7 g/cm 3 , and a maximum compressive strength of 218.03 MPa. This enabled sintering at lower temperatures while maintaining properties comparable to plate‐like corundum. As the modified limestone content increased, the porosity of the product increased, while the bulk density decreased; the compressive strength generally remained high, and it is expected to be used as a lightweight, high‐temperature‐resistant thermal insulation material.
