Si 3 N 4 ceramics were sintered at 1900℃ for 12 h with Y 2 O 3 and MgSiN 2 as sintering aids under 1 MPa nitrogen pressure. The effects of diamond with different particle sizes (1,2 μm) as carbon source on the microstructure, thermal properties and carbothermal reduction behavior of Si 3 N 4 ceramics were systematically studied. The results show that the carbothermal reduction process introduced by diamond significantly reduces the oxygen content and increases the N/O ratio of the secondary phase at the grain boundary. Among them, the sample with 1μm diamond (SNC-1) showed the best reaction efficiency: the fine-grained diamond had a higher specific surface area and stronger reactivity, which promoted the uniform carbothermal reduction reaction and effectively removed the oxygen impurities at the grain boundary. In the final dense Si 3 N 4 ceramics, although the strength of the SNC-1 sample with 1 μm diamond is slightly sacrificed, with the decrease of grain boundary oxygen content, the content of β-Si 3 N 4 increases, the grain morphology develops into a rod shape and the size is obviously coarsened, forming a microstructure that is more conducive to heat conduction. Therefore, SNC-1 achieves a balance between thermal conductivity and mechanical properties, and improves thermal conductivity while maintaining high strength. This is of great significance for the application scenarios that pursue the synergy of high thermal conductivity and good mechanical properties.

In this study, well-dispersed spherical gold powders have been prepared by liquid-phase chemical reduction method. The effects of particle size on the properties of gold electrodes for negative temperature coefficient (NTC) thermistor chip were investigated systematically. The research clarifies the correlation between particle size, microstructure, and service properties, offering a reference for the optimization of electrode materials. SEM, XRD, TGA, and BET were used to characterize gold powder, whereas metallographic microscopy, shear strength, high-temperature storage, and thermal shock test were performed to evaluate the performance of gold electrodes. The results have revealed that variations in particle size (1–2 μm) influence the degree of sintering densification, the gold electrode surface characteristics, and microstructural features (such as the grain size and grain boundary dimensions). Differences in size affect the shear strength, high-temperature storage performance, and thermal shock resistance. A decrease in gold particle size resulted in a slightly lower gold electrode shear strength with an increase in high-temperature storage and a decrease in thermal shock performance. Electrodes fabricated using 1.53 μm gold powder delivered a superior performance with a shear strength of 35.46 gf (0.35N) and 0.34

To improve the comprehensive properties of Si3N4 ceramics, diamond powders with different particle sizes (1 and 2 μm) were added. The effects of diamond particle size on carbothermal reduction behavior, phase evolution, microstructure, and thermomechanical properties of Si3N4 ceramics were systematically investigated. The results show that 1 μm diamond exhibits higher reactivity because of its smaller particle size and larger specific surface area, which promotes the carbothermal reduction of surface silica, decreases oxygen-related impurities, and increases the N/O ratio of the liquid phase. As a consequence, the dissolution–reprecipitation growth of elongated β-Si3N4 grains is enhanced, leading to reduced grain-boundary scattering and improved thermal conductivity. In contrast, 2 μm diamond shows lower reactivity, resulting in insufficient carbothermal reduction, hindered densification, and inferior overall properties. Although the sample containing 1 μm diamond exhibits the highest thermal conductivity, its flexural strength decreases slightly, which is attributed to the combined effects of grain coarsening, reduced intergranular phase, and increased defect sensitivity. These results demonstrate that optimizing diamond particle size is an effective approach for regulating oxygen impurity, microstructure, and overall performance in Si3N4 ceramics.

In this work, high-entropy [(Mg1/3Zn1/3Li1/3)1-x(Co1/2Ni1/2)x]2TiO4-delta (MZLCNT) ceramics (x = 0.0-0.4) were synthesized via a solid-state reaction method. The introduction of low concentrations of Co and Ni significantly increased the configurational entropy (Delta Sconfig) of the ceramics, inducing cation disorder and promoting the system transformation from the stable Mg2TiO4 phase to an entropy-stabilized Zn2TiO4-based high-entropy solid solution in the high-entropy MZLCNT ceramic, as confirmed by Raman spectroscopy. However, excessive Co and Ni contents reduce the cation disorder due to their strong preference for octahedral sites. Meanwhile, reducing the Li+ content effectively suppresses the formation of oxygen vacancies. Based on the complex chemical bond theory (P-V-L theory), the Ti-O bond exhibits significantly higher ionicity and lattice energy than the A-O bond (A = Mg/Zn//Li/Co/Ni), contributing more substantially to the dielectric constant (epsilon r) and quality factor (Qf) of ceramics. Furthermore, the increase in Delta Sconfig significantly reduces lattice distortion, thereby enhancing the bond strength of A(1)-O bonds in tetrahedra and further improving the temperature coefficient of the resonant frequency (tau f) of ceramics. As Delta Sconfig changes, excellent microwave dielectric properties were obtained at 1300 degrees C: epsilon r values of 14.81-16.24, Qf values of 36 700-74 600 GHz, and tau f values of -42 to -18 ppm degrees C-1. The research findings offer promising candidate systems for the development of high-performance and highly stable microwave dielectric materials, while further enhancing the understanding of the high-entropy effect mechanism in ceramics.

A series of (Mg1/2Zn1/2)(0.4+x)(Co1/3Ni1/3Mn1/3)(0.6-x)TiO3 (0.0 <= x <= 0.6) ceramics with configurational entropy (triangle S-config) ranging from 0.69 R to 1.61 R were synthesized via the solid-state reaction with sintering from 1000 degrees C to 1300 degrees C. As entropy increased, the secondary MTi2O5 phase was suppressed, leaving a primary ilmenite MTiO3 (M = Mg, Zn, Co, Ni and Mn) phase at triangle S-config > 1.59 R. Sintering at 1200 degrees C produced ceramics with dielectric constant (epsilon(r)) of approximately 19 and a maximum quality factor (Qf) value of 58,000 GHz at x = 0.5. Furthermore, the temperature coefficient of the resonant frequency (tau(f)) that asymptotically approaches zero, varying from -59 ppm/degrees C to -17 ppm/degrees C. This trend was cross-validated using a high-entropy (Mg0.16Zn0.16Co0.16Ni0.16Mn0.16Li0.2)TiO3-delta ceramics (S-triangle(config) approximate to 1.79 R and tau(f) approximate to -5 ppm/degrees C). This work demonstrates that increased configurational entropy induces [TiO6] octahedron distortion, thereby mediating bond stabilization achieves near-zero tau(f) at lower sintering temperatures in ilmenite-structured ceramics.

In this study, a series of high-entropy [(Mg 1/2 Zn 1/2 ) 0.4+ x (Ni 1/3 Co 1/3 Mn 1/3 ) 0.6- x ] 2 TiO 4 (expressed as MZNCMT) (0.0 <= x <= 0.6) ceramics were prepared via the solid-state reaction, the high-entropy ceramics exhibited inverse spinel structure. The phase compositions, microstructures, and microwave dielectric properties were investigated. The results of x-ray diffraction (XRD) showed that a principal phase of [(Mg 1/2 Zn 1/2 ) 0.4+ x (Ni 1/3 Co 1/3 Mn 1/ 3)0.6-x]2TiO4 ceramics, whereas the second phase of (Mg, Zn, Ni, Co, Mn)TiO3 appeared when x <= 0.4. With the increase of x value, the relative density of the sample decreased, the unit cell volume first decreased and then kept expanding. This phenomenon could be attributed to the reduction of (Ni 1/3 Co 1/3 Mn 1/3 ) 2 + . Good microwave dielectric properties were achieved: x = 0.0 (epsilon r = 17.17, Qf = 16500 GHz, zf = -33 ppm/degrees C), x = 0.5 (epsilon r = 16.30, Qf = 53900 GHz, zf = -30 ppm/degrees C) and x = 0.6 (epsilon r = 16.26, Qf =110800 GHz, zf = -39 ppm/degrees C). The epsilon r value of MZNCMT ceramics is consistent with the theoretical dielectric constant (epsilon theo), indicating that epsilon r is mainly based on ion polarization. The Qf value were highly related to the packing fraction. Furthermore, the zf value depended on the bond strength of A-site.

A series of Sr1‒1.5xLuxTiO3 (x = 0, 0.005, 0.01, 0.015, and 0.02) ceramics was sintered under an air atmosphere through the solid-state reaction method. The results show that doping with Lu3+ considerably enhances material permittivity. The ceramic with x = 0.01 exhibits a colossal permittivity (CP) of ∼101000 with a tanδ of ∼0.16 at a frequency of 1 kHz, demonstrating enhanced stability over a wide temperature (30 to 300 °C) and frequency (102 to 106 Hz) range. Based on the analysis of dielectric relaxation, X-ray photoelectron spectroscopy (XPS), and the universal dielectric response law, the CP effect is primarily due to the formation of defect dipoles, which are correlated with the presence of oxygen vacancies, such as Ti3+ Ti3+, , Ti3+, and Ti3+. These defect dipoles serve to pin electrons, limiting long-range transitions, and enhancing local polarization. Doping with Lu3+ also induces a secondary Lu2Ti2O7 phase, which are characterized by X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS). The results generated in this study can inform the development and application of new CP materials based on SrTiO3.

This study investigates the synergistic enhancement of tantalum (Ta) doping and nitrogen (N-2) annealing on the dielectric properties of Sr(0.98)5Lu(0.01)Ti(1-x)TaxO(3) (x = 0, 0.01, 0.015, and 0.02) ceramics. X-ray diffraction (XRD) confirmed the presence of the primary SrTiO3 phase along with a minor secondary phase of Lu2Ti2O7. XPS, Raman, and UV-vis spectroscopy analyses revealed the formation of defect dipoles including [Ti3+-Lu-Sr(+)], Sr[e '-Ta-Ti(center dot)], and [Ti3+-V-O(center dot center dot)-Ti3+], induced by Ta doping and N-2 annealing. The combined effects of electron-pinned defect dipole (EPDD, obtained from defect dipoles), along with interface polarization (induced by phase boundaries), resulting in ultra-low dielectric loss and excellent thermal stability. Notably, the Sr(0.98)5Lu(0.01)-Ti(0.98)5Ta(0.015)O(3) ceramic, which was sintered in air and subsequently annealed in N-2 at 1325 degrees C, exhibited a high permittivity (epsilon(r) similar to 162,000), ultra-low dielectric loss (tan delta similar to 0.013), and excellent thermal stability (-55 degrees C-125 degrees C, Delta epsilon'/epsilon ' 25 degrees C <= +/- 15 %) at 1 kHz. This study can provide a way to improve the properties of colossal permittivity materials.

This study investigates the dielectric properties of Sr0.985Lu0.01Ti1-xTaxO3 ceramics co-doped with Lu and Ta as dual-donor, which were prepared using a solid-state method and sintered in a nitrogen atmosphere. The XRD results demonstrate that the dual-donor doping of Lu and Ta at Sr and Ti sites, respectively, which will improve the dielectric properties. The optimal dielectric properties were observed when x = 0.01, which the permittivity reaching approximately 220,000 and the dielectric loss is around 0.02. Through XPS and defect chemical analysis, it has been identified that the formation of point defects including (VSr)-Sr-y, (LuTi)-Ti-y, V center dot center dot O and Ti3+ will be produced by sintering in N2-atmosphere and the dual-donor doped of Lu3+ and Ta5+. These point defects aggregate into dipole clusters, such as Ti3+ - V center dot center dot O - Ti3+, (VSr)-Sr-y - V center dot center dot O and (LuTi)-Ti-y - V center dot center dot O - Ti3+, resulting in enhanced EPDD effect and reduced dielectric loss. This work provides valuable insights into the design of advanced dielectric materials with colossal permittivity.

ZnO-B2O3-SiO2-Nb2O5 (ZBSN) glass-ceramics were synthesized via glass melt quenching followed by heat treatment at 700-1050 degrees C. FTIR analysis revealed that the high field strength Nb5+ ions preferentially attracted O2-ions within the glass, competing with B3+, Si4+, and Zn2+ ions to form Nb-O bonds, thereby reinforcing the glass network. In-situ FTIR spectrograms further demonstrated that elevated temperatures promoted nucleation and growth of Si4+ and B3+ ions containing crystalline phases, intensifying the competition for O2-ions among these cations. This process amplified vibrational modes associated with B-O-B and Si-O-Si bonds in the structural units. Increasing the Nb2O5 content enhanced network connectivity, suppressing crystallization and increasing the residual glass phase. Consequently, the sintering temperature decreased progressively, while the coefficient of thermal expansion (CTE) increased. Among the compositions studied, the ZBSN0.5 glass-ceramic sintered at 950 degrees C for 30 min demonstrated optimal properties: CTE = 3.2 ppm/degrees C, epsilon r = 6.2, and Q x f = 19573 GHz.

The TiO2 doped CaNb2O6 ceramics were successfully prepared by solid state reaction in this work. The XRD and Rietveld refinement results of the CaNb2-xTixO6 (0 <= x <= 0.025) showed that Ti4+ entered the Nb5+ lattice site and replaced a part of Nb5+, forming a substitutional solid solution. The XPS results of the CaNb2-xTixO6 ceramics explained that Ti4+ entered the Nb5+ lattice position and caused the formation of oxygen vacancies. Dipoles caused by oxygen vacancies limited the long-range transition of electrons, resulting in electron pinning effect. The SEM results displayed that with the addition of Ti4+, the structure of CaNb2-xTixO6 ceramics densified rapidly. The dielectric constant (epsilon(r)), resonant frequency (tau(f)) and quality factor (Qxf) values were related to density, bond valence, anharmonic motion between atoms and crystallinity, respectively, which provided a theoretical basis for further regulating microwave dielectric properties. When the doping amount of Ti4+ increased from 0.005 to 0.02, the tau(f) value increased from -62 ppm/degrees C to -22 ppm/degrees C. The CaNb2-xTixO6 ceramics with x=0.02 sintered at 1425 degrees C for 4 h had excellent microwave dielectric properties: epsilon(r) = 15.76, Qxf =30397 GHz, tau(f) =-22 ppm/degrees C.

A series of high-entropy ceramics with the nominal composition (Mg0.5Zn0.5)0.4+xLi0.4(Ca0.5Sr0.5)0.4−xTiO3 (0 ≤ x ≤ 0.4) has been successfully synthesized using the conventional solid-phase method. The (Mg0.5Zn0.5)0.4+xLi0.4(Ca0.5Sr0.5)0.4−xTiO3 ceramics are confirmed to be composed of the main phase (Zn,Mg,Li)TiO3 and the secondary phase Ca0.5Sr0.5TiO3 by X-ray diffractometer, Rietveld refinement, and X-ray spectroscopy analysis. The quality factor (Q×f) of the samples is inversely proportional to the content of the Ca0.5Sr0.5TiO3 phase, and it is influenced by the density. The secondary phase and molecular polarizability (αT) have a significant impact on the dielectric constant (εr) of the samples. Moreover, the temperature coefficient of resonant frequency (τf) of the samples is determined by the distortion of [TiO6] octahedra and the secondary phase. The results indicate that (Mg0.5Zn0.5)0.4+xLi0.4(Ca0.5Sr0.5)0.4−xTiO3 ceramics achieve ideal microwave dielectric properties (εr = 17.6, Q×f = 40900 GHz, τf = −8.6 ppm/°C) when x = 0.35. (Mg0.5Zn0.5)0.4+xLi0.4(Ca0.5Sr0.5)0.4−xTiO3 ceramics possess the potential for application in wireless communication, and a new approach has been provided to enhance the performance of microwave dielectric ceramics.

Si3N4 ceramics are highly valued for their exceptional thermal conductivity and mechanical properties. This study investigated the effects of different addition ratios of Y2O3-MgO-MgSiN2 ternary sintering additives on liquid phase viscosity, densification, microstructure, thermal conductivity and mechanical properties. The incorporation of MgSiN2 as sintering additives introduced additional Si and N into the liquid phase, forming a nitrogen-rich liquid phase that promoted the grain growth showing a bimodal distribution. When the MgO/ MgSiN2 ratio reached 2/3, the moderate liquid phase viscosity facilitated enhanced densification and grain growth. This resulted in an increased number of large grains, a moderate grain size distribution, and a good bimodal microstructure. Consequently, the 2M3N exhibited superior properties, including a thermal conductivity of 105.22 W m-1 K-1, a fracture toughness of 5.91 MPa m1/2, and a bending strength of 726.12 MPa. The study demonstrates that precise control of the Y2O3-MgO-MgSiN2 ratio can effectively regulate the microstructure, leading to improved thermal and mechanical performance.

In this work, the ceramics of Sr(Ta 1/2 Al 1/2 ) x Ti 1-x O 3 (x = 0 %, 0.5 %, 1 %, 2 %, 3 %, 4 %, and 5 %) were produced through the solid-state reaction and sintered under N 2 atmosphere. The frequency coefficient of permittivity and dielectric loss for the sample with x = 4 % is blow |24%| and |26%|, respectively, within the frequency of 1 kHz to 1 MHz. This demonstrates favorable frequency stability in the dielectric properties. The sample with x = 4 % exhibits remarkable permittivity (e r - 125,000 @ 1 kHz, e r - 95,000 @ 1 MHz) and low dielectric loss (tan delta - 0.054 @ 1 kHz, tan delta - 0.044 @ 1 MHz) were achieved at room temperature. Through the analysis of HAADFSTEM, XPS, it is concluded that and dielectric relaxation, the colossal permittivity effect is primarily attributed to defect clusters associated with oxygen vacancies such as Ti 3+ - V center dot center dot O - Ti 3+ . The clusters of defect dipoles exert a pinning effect on freedom electrons, constraining their long-range transition and improving the dielectric properties. This study lays the foundation for advancing the electronic components, making a significant milestone in technological advancements.

In this study, a two-step method combining the direct foaming process with the control of solid content and heat treatment temperature was employed to prepare ZrP2O7-CePO4 composite porous materials with varying porosities. The results indicate that an increase in solid content and heat treatment temperature leads to a reduction in porosity and average pore size while simultaneously improving the mechanical properties. The porosities, compressive strengths, thermal conductivities, epsilon and Tan delta ranged from 63.2 to 85.3 vol%, 19.43 to 0.99 MPa, 0.089 to 0.088 W/(mK), 1.64 to 2.72, and 0.88 x 10(-3) to 1.99 x 10(-3), respectively. Electromagnetic simulations have validated that ZrP2O7-CePO4 composite porous ceramics, when used as the core layer material for A-sandwich antenna radomes, exhibit excellent transmittance properties. This suggests the potential application of these materials for supersonic aircraft antenna radomes.

The sintering shrinkage behavior, viscosity, microstructures, phase composition, dielectric properties and chemical compatibility with Ag of a novel low-temperature co-fired ceramic (LTCC) material, (1-x) CaO-B2O3- SiO2-ZrO2(CBSZ) + x Ca0.99Cu0.01SiO3 (x = 0, 5, 10, 15 and 20 wt%) glass/ceramics were discussed. The partial dissolution of the Ca0.99Cu0.01SiO3 ceramic powder in CBSZ glass will form additional liquid phase and make viscosity decrease, which could promote the densification of CBSZ/Ca0.99Cu0.01SiO3 composite. The introduction of Ca0.99Cu0.01SiO3 will form heterogeneous nucleus and promote the crystallization of samples. The CBSZ/ Ca0.99Cu0.01SiO3 composite with 10 wt% Ca0.99Cu0.01SiO3 content sintered at 875 degrees C for 30 min has a dielectric constant epsilon r = 6.05, a dielectric loss tan delta = 1.18 x 10-3 @ 13.76 GHz, flexural strength = 176 MPa, CTE = 7.7258 x 10-6/degrees C, and shows good chemical compatibility when co-fired with Ag electrode. These results indicate that CBSZ glass/Ca0.99Cu0.01SiO3 ceramic composites have a potential to meet the demand of LTCC applications.

CaO-B2O3-SiO2-Nb2O5 (CBSN) glass-ceramics were produced by melt water quenching and isothermal heat treatment in this paper. The FTIR results showed that with the addition of Nb2O5, the combination of B-O and SiO would be destroyed, resulting in a decrease in the number of [BO31 and [SiO41 units. The results about DSC of glass powder showed that with the increase of Nb2O5 doping amount, the softening temperature (Tg) of glass, the initial temperature of the crystallization peak (Tc), the temperature corresponding to the endothermic peak intensity (Tp) of exothermic peaks and the activation energy values of the CaSiO3 and CaB2O4 crystal phase moved to high values, indicating that the crystallization of the CaSiO3 and CaB2O4 phase became difficult. The results of crystallization kinetics showed that the nucleation rate and crystallization rate decreased near Tc1 and Tc2, indicating that the crystal phase crystallization near Tc1 and Tc2 was inhibited. The critical cooling rate decreased with the addition of Nb2O5, indicating that the viscosity of the glass system increased. The XRD results of glassceramics showed that the main crystal phase of the sample changed from & alpha;-CaSiO3 to B-CaSiO3 and finally to CaNb2O6 with the addition of Nb2O5.The CBSN2 glass-ceramics sintered at 865 degrees C for 15 min had excellent dielectric properties: er = 6.42 and tan & delta; = 1.049 x 10-3 (1 MHz). The results indicated that CBSN glass-ceramics could be a potential LTCC substrate material.

ZnO-B2O3-SiO(2)glass -ceramics, with the same Si/B molar ratio (0.7) and different Zn/B molar ratios (1.6-2.1) have been prepared by quenching glass melt and heat treatment between 680 C and 720 degrees C. DSC analysis has demonstrated that the crystallization activation energy (Ea) of the Zn2SiO4 phase increased with increasing Zn/B ratio, and the glass crystallization process was transformed from a two-dimensional to a one-dimensional growth. DSC curves are consistent with the deformation and viscosity curves and can be attributed to the crystallization behavior of glass. The glass -ceramic with Zn/B = 1.7 sintered at 700 C for 30 min exhibited the best properties: epsilon(r )= 6.35; tan delta = 4.3 x 10(-3) (11.39 GHz); CTE = 3.8 x 10(-6) /K.

The dielectric ceramics of Ca 1− x Cu x SiO 3 ( x = 0 − 0.025) were prepared by solid-phase reaction method. The effects of Cu doping on phase composition, crystal structure, and dielectric properties of CaSiO 3 ceramics were investigated. XRD results indicated that appropriate content of Cu doping could suppress impurity phases and obtain pure α-CaSiO 3 calcined powders. After sintering, α-CaSiO 3 phase was the main phase accompanied with a small quantity of impurity phases in undoped ceramics, which transformed to the single β-CaSiO 3 phase after Cu doping. The phase transformation could be attributed to the change of the geometric position of SiO 4 tetrahedron. SEM images showed that grain morphology changed from irregular and loose particles to dense lath by Cu doping. The Ca 0.985 Cu 0.015 SiO 3 ceramics sintered at 1125 °C exhibited excellent dielectric properties: ε r = 5.22, Q × f = 18,948 GHz, τ f = − 63 ppm/°C, and these make the ceramics promising for use in microwave applications.

CaO-B2O3-SiO2-Ta2O5 (CBST) glass-ceramics, with different Ta2O5 content, (up to 6 mol%), have been prepared by using glass melt quenching followed by heat treatment between 800 and 880 degrees C. The Fourier Transform Infrared (FTIR) results showed that the stronger the attraction of Ta5+ to the oxygens in the BO33- and SiO32- structures, the more easily the B-O and Si-O bonds will be destroyed. The underlying reason is most probably the high field strength of Ta5+, which results in a weakening of the vibration intensities of the [BO3] and [SiO4] units. Moreover, the Differential Scanning Calorimetry (DSC) results showed that the softening point (T-g), crystallization starting temperature (T-c1), and exothermic crystallization peak temperature (T-p1), of the CaSiO3 phase, shifted to higher values with the addition of Ta2O5. Also, the crystallization activation energy (Ea) and the glass stability factor (Delta T) of the CaSiO3 phase increased, which indicated that the CaSiO3 phase of the glass became inhibited by the addition of Ta2O5. It was, thus, obvious that there was a need of glass characterization. The results of the crystallization kinetics showed that the critical cooling rate decreased with the addition of Ta2O5, which indicated that the viscosity of the system had increased. The CBST glass-ceramics, containing 1 mol % Ta2O5, that were sintered at 875 degrees C for 15 min showed excellent dielectric properties: epsilon(r) = 6.22 and tan delta = 1.19 x 10(-3) (1 MHz). To sum up, CaO-B2O3-SiO2-Ta2O5 glass-ceramics are potential low temperature co-fired ceramic substrate materials.