Formation mechanism of core–shell structures in Mg-doped BaTiO 3 -based ceramics for high-temperature MLCCs application

Second-Phase Grain Boundary Engineering in Al2O3-MgAl2O4 Composites: Microstructure and Dielectric Breakdown Reliability

Highlights A dual-pathway mechanism governs in situ MgAl2O4 spinel formation in alumina matrix. The optimal kaolin/MgO ratio of 4:1 yields a 17.74 kV/mm characteristic breakdown strength. Excess MgO incorporates into glassy phase, inducing ionic conduction channels. A microstructure–defect–breakdown correlation model is established and provides a theoretical basis for optimizing low-cost alumina energy storage ceramics. Abstract The escalating demands of pulsed power technology and high-energy-density capacitors necessitate dielectric ceramics with simultaneously enhanced breakdown reliability and microstructural homogeneity. Herein, Al2O3-MgAl2O4 composites were fabricated via a solid-state reaction using 80 wt% α-Al2O3 with kaolin/MgO mass ratios of 7:1, 4:1, and 1:1. XRD presents a dual-pathway spinel formation mechanism. SEM reveals 2–5 μm columnar spinel grains uniformly dispersed at grain boundaries. Porosity decreased from 4.29% to 2.69% while grain size increased from 3.35 to 5.64 μm as MgO content rose. Weibull analysis (n ≥ 10) showed that the 4:1 group achieved optimal dielectric reliability with a characteristic breakdown strength of 17.74 kV/mm and a Weibull modulus of 16.07, representing 8.76% and 20.93% improvements over the 7:1 (16.31 kV/mm, m = 24.58) and 1:1 (14.67 kV/mm, m = 15.37) groups, respectively. The 4:1 composition balanced grain boundary pinning (4.61 μm) and residual porosity (3.59%), maximizing interfacial charge scattering. Excess MgO (1:1) introduced residual Mg2+ into the glassy phase, inducing ionic conduction and premature breakdown. This study establishes a quantitative “microstructural composition–defect size distribution–dielectric breakdown” correlation, providing a theoretical foundation for microstructural optimization of low-cost alumina-based energy storage ceramics.

Characterization of Al2O3 Based CMC Reinforced with ZrO2 Particles Fabricated by Powder Metallurgy Technique

This study evaluates the effect of addition of 3 mol% yttria-stabilized zirconia (3Y-TZP) in amounts of 5, 10, 15, and 20 wt.% on microstructure and phase evolution, densification behavior, and mechanical properties of alumina-based ceramic matrix composites. Composite specimens were fabricated using powder metallurgy techniques via uniaxial compaction and sintering at temperatures of 1500°C, 1550°C, 1600°C, and 1650°C for a dwell time of 2-hour. Phase composition and microstructural characteristics were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM), while densification behavior was evaluated through Archimedes’ principle. Mechanical performance was assessed using flexural strength, fracture toughness, and Vickers hardness tests. The results indicated that higher sintering temperatures promoted densification effect through vacancy diffusion and pore elimination. While the addition of zirconia restrained alumina grain coarsening through pinning of grain boundary migration, causing the composite having 20 wt.% zirconia to exhibit the highest relative density of about 97.5% when sintered at 1600°C. Mechanical properties improved progressively with increasing zirconia content up to 15 wt.%, where flexural strength reached about 438 MPa, fracture toughness increased to about 6.6 MPa·m½, and Vickers hardness of about 1770 HV, corresponding to enhancement percentages of about 20.5%, 41%, and 4.5%, respectively.

Defect-engineered colossal permittivity behavior in Dy-doped BaTiO3 ceramics via synergistic control of doping, sintering temperature, and atmosphere

Composition-dependent wetting and interfacial behavior of CMAS melts on YSZ thermal barrier coatings: a molecular dynamics and first-principles study

The corrosion of yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBCs) induced by molten calcium–magnesium–aluminosilicate (CMAS) deposits is closely related to interfacial wetting and diffusion behaviors. In this work, the effects of CMAS composition on the wetting and corrosion behavior of YSZ TBCs were investigated using molecular dynamics simulations combined with first-principles calculations. Single-component oxide melts (CaO, MgO, Al2O3, and SiO2) and designed CMAS melts with varied compositions were constructed on the YSZ (010) surface to clarify the role of individual elements. The results show that CaO exhibits the lowest equilibrium contact angle (20.3°) and the highest diffusion coefficient, indicating a strong wetting and penetration tendency. For designed CMAS compositions, increasing Ca content leads to a continuous decrease in contact angle and an increase in adsorption work, with Ca6Mg2AlSi6O22 showing the strongest interfacial adhesion. Electronic structure analysis reveals that the enhanced interfacial activity originates from strong interactions among Ca, O, and Y atoms near the Fermi level. These results provide atomic-scale insight into the composition-dependent wetting mechanisms of CMAS melts on YSZ surfaces within a simplified YSZ(010)-based model framework, and may offer theoretical guidance for improving CMAS resistance of thermal barrier coatings.

Impact of MgO Additions on the Oxidation Resistance and Compression Behavior of Vanadium Alloys

A novel route for the fabrication of core–shell structured V–MgO alloys via in situ MgO formation is developed. Spark plasma sintering is employed to obtain fully dense V– x MgO ( x  = 1, 2.5, 5 wt.%) samples. The sintered alloys consist of vanadium grains with finely dispersed MgO particles uniformly distributed along the grain boundaries. An increase in oxidation resistance at 600 °C is achieved for alloys containing more than 2.5 wt.% MgO. XRD analysis shows that during oxidation, V 2 O 5 reacts with MgO, leading to the formation of MgO 6 V 2 and Mg 2 O 7 V 2 oxides. However, these compounds formed at high temperature are not stable in ambient air with atmospheric CO 2 since it forms MgCO 3 . For further development of this concept, other more stable vanadate formers need to be investigated. The room temperature compressive strength increases from 1350 MPa for pure vanadium to 2180 MPa for the V–5MgO alloy, while at 600 °C it increases from 300 to 350 MPa.

Investigating the impact of Sm3+/Ni2+ co-doping on the dielectric behaviour of CaCu3Ti4O12 ceramics for microelectronic applications