Microstructures and Microwave Dielectric Properties of Bi2O3‐Deficient Bi12SiO20 Ceramics

The Microstructure and microwave dielectric properties of Bi₂O₃‐deficient Bi₁₂SiO₂₀ ceramics were investigated. A small amount of unreacted Bi₂O₃ phase melted during sintering at 825°C and assisted with densification and grain growth in all samples. The melted Bi₂O₃ reacted with remnant SiO₂ during cooling to form a Bi₄Si₃O₁₂ secondary phase. The nominal composition of Bi_11.8SiO_19.7 ceramics sintered at 825°C for 4 h had a high relative density of 97% of the theoretical density, and good microwave dielectric properties: ε_r = 39, Q × f = 74 000 GHz, and τ_f = ?14.1 ppm/°C. Moreover, this ceramic did not react with Ag at 825°C.     

Density,viscosity and surface tension of high-silicate CaO–SiO2 and CaO–SiO2–Fe2O3 slags derived by aerodynamic levitation. The behavior of Fe3+ in high-silicate melts

Thermophysical data for liquid slag are required for the optimization and control of metallurgical processes. The density, surface tension and viscosity were measured by employing aerodynamic levitation under contactless conditions. The high-silicate slag (44 and 63 mass-% of SiO₂) of the CaO–SiO₂ and CaO–SiO₂–Fe₂O₃ systems (with 5 and 10 mass-% Fe₂O₃) was investigated under (80% Ar + 20% O₂) gas atmosphere. The temperature ranges were between 800 °C and 2000 °C for the density and 1500 °C–2000 °C for surface tension and viscosity measurements. The influence of the CaO/SiO₂ ratio on the investigated properties and the behavior of Fe³⁺ ions in high-silicate melts were examined. The density of the CaO–SiO₂ melt was lower than that of the CaO–SiO₂–Fe₂O₃ systems. The surface tension of all compositions tested decreased with temperature and showed compositional dependence. The viscosity measured was higher in the Fe₂O₃-containing slag. The Raman spectroscopy analyses confirmed the increase in the degree of polymerization with the addition of Fe₂O₃ for the silicate-rich slag. The formation of a complex anion of a ferric ion and contribution to the silicate network were assumed. The trends observed were related to the structural properties and different interionic bonding. Urbain's viscosity model and FactSage? 7.3 were applied for the assessment of the experimental data.     

Low-temperature joining of SiC ceramics with Y2O3-Al2O3 interlayer by SiO2-based liquid phase extrusion strategy

In order to reduce the joining temperature of SiC ceramics by glass-ceramic joining, some oxides were usually introduced into to Y₂O₃–Al₂O₃ for reducing the eutectic temperature. However, the joints might have poor high-temperature resistance due to the low melting point of the joining layer. In the present work, based on novel SiO₂-based liquid phase extrusion strategy, joining of SiC ceramics with Y₂O₃–Al₂O₃ interlayer was carried out by using Y₂O₃–Al₂O₃–SiO₂ as the filler through spark plasma sintering (SPS). The SiO₂-free interlayer of Y₂O₃–Al₂O₃ was used for comparison. It was found that SiC joints using Y₂O₃–Al₂O₃ could be only joined at a high temperature of 1800 °C, and the thickness of the interlayer was about 20 μm. The shear strength of the joint obtained at 1800 °C was 89.62 ± 4.67 MPa and the failure located in the SiC matrix. By contrast, reliable joining of SiC ceramics could be finished at as low as 1550 °C by extrusion of SiO₂-containing liquid phase when using Y₂O₃–Al₂O₃–SiO₂ as the interlayer, alongside the interlayer thickness of only several microns. The joint strengths after joining at 1550 °C was 84.90 ± 3.48 MPa and the failure located in matrix position. The joining mechanism was discussed by combining the detailed microstructure analysis and phase diagram.     

Dielectric polarizability of SiO2 in niobiosilicate glasses

Understanding the mechanisms contributing to dielectric properties of glasses is critical for designing new compositions for microwave frequency applications. In this work, dielectric permittivity was measured using a cavity perturbation technique at 10 GHz for a series of niobiosilicate glasses with the compositions (100-2x)SiO₂- xNb₂O₅- xLi₂O where x = 32.5, 30, 25, and 15 mol%. Permittivity measurements and glass compositions were used to calculate the polarizability of each cation-anion unit in the glass network using the Clausius-Mossotti equation. The SiO₂ polarizability in niobiosilicates was calculated to be 6.16 ų, which is much higher than the SiO₂ polarizability in fused silica glass (5.25 ų), alkali modified silicates (5.37 ų), and aluminosilicates (5.89 ų). The increasing trend in SiO₂ polarizability is attributed to the disruption in the connectivity of the SiO₄ tetrahedral network as it accommodates different network formers. The high SiO₂ polarizability of 6.16 ų accurately predicts measured dielectric permittivity when Nb₂O₅ = 25, 30, and 32.5 mol%, but overpredicts measured permittivity when Nb₂O₅ ≤ 15 mol%, which is attributed to a decrease in SiO₂ polarizability as the percentage of corner sharing SiO₄ tetrahedra with NbO₆ octahedra goes down. This work demonstrates that SiO₂ polarizability depends on chemistry and connectivity of the glass, which has important implications in designing glass compositions for microwave frequency applications.     

Ultra‐Low Temperature Sintering and Dielectric Properties of SiO2‐Filled Glass Composites

Ultra low temperature co‐fired ceramics system based on zinc borate 3ZnO–2B₂O₃ (3Z2B) glass matrix and SiO₂ filler was investigated with regard to the phase composition, the microstructure and the dielectric properties as functions of the filler content and sintering temperature. The softening temperature of 554°C and the crystallization temperature of around 650°C for the glass were confirmed by Differential Thermal Analysis result. The X‐ray diffraction results show that all SiO₂‐filled samples were made up of SiO₂, α‐Zn(BO₂)₂, Zn₃B₂O₆ phases. And there was no chemical reaction between SiO₂ and the glass during densification. And then the dielectric constant decreased with the increasing content of SiO₂. At the level of 15 wt% SiO₂ addition, the composites can be densified at a sintering temperature of 650°C for 30 min, and showed the optimal dielectric properties at 1 MHz with the dielectric constant of 6.1 and the dielectric loss of 1.3 × 10^?3, which demonstrates a good potential for use in LTCC technology.     

Effect of boron oxide on the microstructure of mullite-based glass-ceramic glazes for floor-tiles in the CaO–MgO–Al2O3–SiO2 system

The effect of increasing replacement of Al₂O₃ by B₂O₃ in a parent glass on the sintering and further crystallization of mullite was investigated. The composition of the parent glass was chosen in the mullite primary phase field of the CaO–MgO–Al₂O₃–SiO₂ quaternary system. Glass powder pellets were heated under standard (10 °C/min and 2 h of hold time) and fast heatings (25 °C/min and 5 min of hold time) at different temperatures from 700 to 1190 °C. Sintering of B₂O₃-containing glasses took place in the range between 850 and 1050 °C. X-ray diffraction results showed that mullite formed as unique crystalline phase for glasses containing amounts of B₂O₃ larger than 6 wt%. For lower amounts of boron oxide cordierite was formed as secondary crystalline phase. Quantitative determination of mullite by Rietveld analysis indicated that the higher amount of mullite present in the glass-ceramic fast heated at 1160 °C was 19.5 wt% for the glass containing 9 wt% of B₂O₃. The final microstructure of the glass-ceramic glazes showed the presence of well shaped, long acicular mullite crystals dispersed within the residual glassy phase. Results of glass-ceramic glazes when applied as slurry and under industrial heating conditions pointed out promising mechanical properties.     

Interactions between Ca2Gd8(SiO4)6O2 apatite and calcium-magnesium-aluminosilicate (CMAS) at elevated temperatures

High temperature corrosion behavior of Ca₂Gd₈(SiO₄)₆O₂ (CGdS) apatite has been investigated in the presence of molten calcium-magnesium-aluminosilicate (CMAS) glass having the composition 21.9 CaO - 4.3 MgO - 5.4 Al₂O₃ - 63.0 SiO₂ - 4.3 Na₂O - 0.8K₂O - 0.1 Fe₂O₃ (weight %). CGdS apatite powder was prepared by solid state synthesis from constituent oxides. Pellets of CGdS apatite + CMAS mixed powder and CGdS-CMAS diffusion couples were annealed at 1200, 1300, 1400, and 1500 °C for 1 and 20 h in ambient atmosphere. Development of phases in heat treated specimens was characterized using various analytical techniques as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high angle annular dark field imaging, selected area electron diffraction and energy dispersive X-ray spectroscopy. In both pellets and diffusion couples, monoclinic cyclosilicate Ca₃Gd₂(Si₃O₉)₂ formed from reaction of apatite with CaO in the CMAS melt only in samples heat treated at 1200 °C for 1 and 20 h or at 1300 °C for 1 h. Triclinic CaSiO₃ and monoclinic diopside MgCaSi₂O₆ were also observed in samples annealed at 1200 and 1300 °C. At 1400 and 1500 °C, because of its low viscosity, CMAS infiltrated along the pores and grain boundaries of the apatite substrates in diffusion couples. Phase compositions predicted from thermochemical computation were in good agreement with those observed experimentally. Ca₂Gd₈(SiO₄)₆O₂ apatite has the potential for being an effective T/EBC in circumventing the penetration of molten CMAS up to about 1300 °C but not at higher temperatures.     

Phase Equilibria of the SiO2–V2O5 system

The SiO₂–V₂O₅ system is one of the key systems for vanadium extraction and applications of vanadium oxides in the ceramic industries. However, only limited data in this system and contradictive results were reported from preceding studies. In the present study, high-temperature phase equilibrium experiments were conducted to construct the phase diagram of SiO₂–V₂O₅ system at temperature range of 660–1100 °C. Electron probe X-ray micro-analyzer (EPMA) was used to analyze the microstructure and composition of the phases presented in quenched samples. The liquidus temperatures in both SiO₂ and V₂O₅ primary phase field were determined. The eutectic temperature is confirmed to be within 670–680 °C and the eutectic composition comprises 1.9 wt% SiO₂. SiO₂ phase contains up to 1.4 wt% V₂O₅ in the temperature range investigated.     

Preparation of α-cordierite through mechanochemical activation of MgO–Al2O3–SiO2 ternary system

Samples of the ternary system MgO–Al₂O₃–SiO₂ with stoichiometric composition in relation to α-cordierite (Mg₂A_l4Si₅O₁₈), consisting of 22.2 mol% MgO, 22.2 mol% Al₂O₃, and 55.6 mol% SiO₂, were activated in a low energy mill with a constant speed of 100 rpm, in an aqueous medium. The precursors used were corundum (Al₂O₃), silica gel HF254 type 60 (SiO₂), and periclase (MgO). The objective of the present study was to evaluate the effect of mechanochemical activation on the solid-state synthesis of α-cordierite, using a low energy ball mill. Another objective was to shed light on the effect of mechanochemical activation on the steps of α-cordierite formation. For this end several grinding conditions were evaluated, varying the time and mass ratio of precursors/grinding elements, as well as calcination at different temperatures between 950 °C and 1350 °C for 2 h. The samples were analyzed for the determination of the formed phases by Infrared (IR) and X-ray Diffraction (XRD). The phases identified in uncalcined samples were brucite (Mg(OH)₂), forsterite (Mg₂SiO₄), enstatite (MgSiO₃), spinel (MgAl₂O₃), amorphous silica (SiO₂), corundum (α-Al₂O₃), and zirconia (monoclinic and tetragonal ZrO₂). The lowest temperature corresponding to the formation of α-cordierite (α-Mg₂Al₄Si₅O₁₈) was 1150 °C and a considerable amount of this phase (16.2%) was observed at this temperature, for the sample with the higher mechanochemical activation. In a solid-state reaction, α-cordierite is normally obtained at around 1400 °C, therefore, the formation of this phase at 1150 °C confirms that the mechanochemical activation method, using a low-cost ball mill, is efficient in reducing the solid-state reaction temperature.     

Structure,crystallization, and performances of alkaline-earth boroaluminosilicate sealing glasses for SOFCs

We study the structure, crystallization, and performances of the sealing glasses with the composition (mol.%) of 12Al₂O₃·8B₂O₃·40SiO₂·40RO (R = Mg, Ca, Sr) for solid oxide fuel cells (SOFCs) before and after isothermal treatment at 700°C, which is within the operation temperature range (600-800°C) of SOFCs. The crystallization behavior has been investigated by differential scanning calorimetry and X-ray diffraction under both dynamic and isothermal conditions. The structural evolution is probed using the Raman and nuclear magnetic resonance spectroscopies. The performances of the sealing glasses are characterized in terms of the coefficient of thermal expansion, the crystallization-induced stress at glass–steel interface. We find that strong crystallization occurs at the operation temperature (700°C) far below the crystallization onset temperature measured by DSC. The structure origin of this anomalous crystallization is discussed in terms of structural heterogeneity of the three studied glasses. We determine the residual stress at the interface between the Ca-containing glass and the steel after isothermal treatment at 700°C for 48 h, but this stress does not lead to falling off the glass layer from the steel. This indicates that this glass is a good candidate to be applied in SOFCs.     

Properties of TiB2–PSO modified SiHfBCN-based adhesive through polymer-derived-ceramic route

High temperature SiHfBCN-based ceramic adhesives are fabricated by polymer derived ceramic route with SiHfBCN precursors, TiB₂ and polysiloxane (PSO). The phase composition and microstructure were investigated by X-ray diffraction and scanning electron microscopy, respectively and the evolution of pores was analyzed by Micron X-ray 3D Imaging System and VG Studio MAX 3.0.2 software. After heat-treating at 80 °C and curing at 170 °C in air, the adhesion strength detected in air of SiHfBCN adhesives is 3.22 MPa at room temperature (RT) and can rise to 5.47 MPa at 1000 °C after pyrolysis at 1000 °C in air for 2 h with a universal testing machine. By modifying SiHfBCN with TiB₂–PSO, the adhesion strength can be enhanced to 9.49 MPa at RT and 6.37 MPa at 1000 °C. The results indicate that the formation of SiO₂–B₂O₃–TiO₂ ternary glasses play an important role in improving the adhesion strength. The present study broaden the high temperature adhesive family suitable for large-scale complex ceramic components in harsh environments.     

Gel-derived SiO2–CaO–P2O5 bioactive glasses and glass-ceramics modified by SrO addition

The effect of SrO substitution for CaO in two sol–gel glasses with different chemical compositions (mol%) A2Sr: (54−x)CaO–xSrO–6P₂O₅–40SiO₂ and S2Sr: (16−x)CaO–xSrO–4P₂O₅–80SiO₂ (x=0, 1, 3 and 5) stabilized at 700 °C on their structure (XRD, FTIR) and bioactive properties (SBF test) was investigated. Preliminary in vitro tests using human articular chondrocytes of selected A2Sr glass were also conducted. Moreover, the subject of this study was to detect the changes on material properties after heat treatment at 1300 °C. The results show that the effect of strontium substitution on structure, bioactivity and crystallization after treatment at both the above temperatures strongly depends on CaO/SiO₂ molar ratio. The presence of 3–5 mol% of strontium ions creates more expanded glass structure but does not markedly affect crystallization ability after low temperature treatment. Sintering at 1300 °C of A2 type glasses results in crystallization of pseudowollastonite, hydroxyapatite and also Sr-substituted hydroxyapatite for 3–5 mol% of SrO substitution. The increase of strontium concentration in silica-rich materials after sintering leads to appearance of calcium strontium phosphate instead of calcium phosphate. Bioactivity evaluation indicates that substitution of Sr for Ca delays calcium phosphate formation on the materials surface only in the case of silica-rich glasses treated at 700 °C. Calcium-rich glasses, after both temperature treatments, reveals high bioactivity, while crystal size of hydroxyapatite decreases with increasing Sr content. High temperature treatment of high-silica glasses inhibits their bioactivity. Preliminary in vitro tests shows Sr addition to have a positive effects on human articular chondrocytes proliferation and to inhibit cell matrix biomineralization.     

Cyclic thermal shock resistance of h-BN composite ceramics with La2O3–Al2O3–SiO2 addition

The effects of La₂O₃–Al₂O₃–SiO₂ addition on the thermal conductivity, coefficient of thermal expansion (CTE), Young's modulus and cyclic thermal shock resistance of hot-pressed h-BN composite ceramics were investigated. The samples were heated to 1000 °C and then quenched to room temperature with 1–50 cycles, and the residual flexural strength was used to evaluate cyclic thermal shock resistance. h-BN composite ceramics containing 10 vol% La₂O₃–Al₂O₃ and 20 vol% SiO₂ addition exhibited the highest flexural strength, thermal conductivity and relatively low CTE, which were beneficial to the excellent thermal shock resistance. In addition, the viscous amorphous phase of ternary La₂O₃–Al₂O₃–SiO₂ system could accommodate and relax thermal stress contributing to the high thermal shock resistance. Therefore, the residual flexural strength still maintained the value of 234.3 MPa (86.9% of initial strength) after 50 cycles of thermal shock.     

High-Temperature thermochemical interactions of molten silicates with Yb2Si2O7 and Y2Si2O7 environmental barrier coating materials

The thermochemical behavior of EBC candidate materials yttrium disilicate (Y₂Si₂O₇) and ytterbium disilicate (Yb₂Si₂O₇) was evaluated with three calcium-magnesium-aluminosilicate (CMAS) glasses possessing CaO:SiO₂ ratios relevant to gas turbine systems. Pellet mixtures of 50 mol% EBC powder to 50 mol% CMAS glass powder were heat treated at 1200°C, 1300°C, and 1400°C. The products of these interactions were evaluated using X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. Above glass melting temperatures, exposure of the disilicates primarily resulted in dissolution into the molten glass followed by precipitation of a Ca₂RE₈(SiO₄)₆O₂ (RE = Yb³⁺, Y³⁺) apatite-type silicate and/or rare earth disilicate. In glasses with high CaO concentrations, apatite readily forms while the disilicate material is consumed by the reaction. As CaO content decreases, the disilicate phase becomes the main reaction product. Overall, reactions with yttrium disilicate favored more apatite crystallization than ytterbium disilicate. The viability of using these disilicates in various operating environments is discussed.     

Isothermal phase diagram of CaO–SiO2–Nb2O5-5wt% Fe2O3–TiO2 system at 1200 °C

The lack of thermodynamic data such as the phase diagram of CaO–SiO₂–Nb₂O₅–Fe₂O₃–TiO₂ system has seriously hampered the comprehensive utilization of niobium, titanium and other resources in the Bayan Obo tailing. In this study, phase equilibria of the CaO–SiO₂–Nb₂O₅–Fe₂O₃–TiO₂ system at 1200 °C were investigated using high temperature equilibrium experiment for the first time, and the CaTiO₃–Ca₁₀Nb₂Si₆O₂₇–Ca₂SiO₄–Ca₂Nb₂O₇ solid phase coexistence region was determined. Afterwards, based on the high temperature equilibrium experiments, the liquidus surfaces of the liquid + CaTiO₃ and liquid + SiO₂ equilibrium coexistence regions in CaO–SiO₂–Nb₂O₅-5wt% Fe₂O₃–TiO₂ system at 1200 °C were calculated using mathematical methods of interpolation and fitting. Finally, the 1200 °C isothermal phase diagrams of CaO–SiO₂–Nb₂O₅-5wt%Fe₂O₃–TiO₂ system were plotted. The results of the study can provide theoretical guidance for the enrichment and extraction processes of niobium and titanium resources in the Bayan Obo tailing.     

Structural,mechanical, and in vitro characterization of freeze-cast scaffolds prepared using a sol-gel-derived bioactive glass from the SiO2–CaO–Na2O–P2O5–K2O–MgO system

This work deals with the preparation of freeze-cast scaffolds using a bioactive glass from the SiO₂–CaO–Na₂O–P₂O₅–K₂O–MgO system. This material could be sintered at lower temperatures (650 °C) than other variations of bioactive glasses, which is an important advantage in terms of energy and cost savings. This behavior represents a great advantage in terms of energy and cost savings. The freeze-casting step was conducted using water as a solvent and liquid nitrogen as a coolant. The prepared samples were examined according to their pore structure, thermal behavior, mechanical stability, and bioactivity. The glass transition temperature (T_g), crystallization onset temperature (T_x), and maximum crystallization temperature (T_c) evaluated for this bioactive glass were about 660 °C, 690 °C, and 705 °C. Consequently, the freeze-cast scaffolds could be sintered at 650 °C for 2–8 h, which favored viscous flow sintering without crystallization. Bioactivity assays were conducted by soaking the scaffolds in simulated body fluid for up to 21 days, showing that these materials present a bioactive behavior, inducing hydroxyapatite formation. These materials' mechanical properties and biocompatibility make them promising candidates for use in trabecular bone repair.     

Ultra-low core loss FeSiAl soft magnetic composites with in-situ double oxidation layers of outer Fe3O4 layer and inner super-thin Al2O3/SiO2 hybrid layer

How to synchronously reduce eddy current loss and hysteresis loss still remains a challenge for achieving low core loss of soft magnetic composite (SMC). In-situ surface oxide effectively combines the formation of insulating layer and the release of internal stress during the molding process. In this study, FeSiAl SMC has been fabricated by powder metallurgy method with in-situ oxidated FeSiAl powder, in which FeSiAl powder are covered by outer Fe₃O₄ insulating layer and inter super-thin Al₂O₃/SiO₂ hybrid layer. Fe₃O₄ layer alleviates dilution magnetic effect, ensuring high saturated magnetization and effective permeability. The super-thin Al₂O₃/SiO₂ hybrid layer enhances electrical resistance, reducing eddy loss. Effects of the in-situ oxidation time on insulating layer and soft magnetic performances of SMC are investigated in detail. Synchronous reduction of eddy current loss and hysteresis loss is achieved through high resistance accompanied with proper insulating layer thickness and low coercive force provided by the special microstructure. For powder with 90 min oxidation at 500 °C, core loss of SMC is low up to 64 mW/cm³ at 50 mT and 100 kHz and 363 mW/cm³ at 100 mT and 100 kHz, while the permeability is kept at 50 until 1100 kHz and is stable until 140 °C. Meanwhile, DC bias performance reaches 51.2% at 100 Oe applied field and Q value is 104.8 at 400 kHz.     

A Complete Solid Solution with Rutile‐Type Structure in SiO2–GeO2 System at 12 GPa and 1600°C

High pressure and temperature synthesis of compositions made of (Si_1?x,Ge_x)O₂ where x is equal to 0, 0.1, 0.2, 0.5, 0.7, and 1 was performed at 7–12 GPa and 1200–1600°C using a Kawai‐type high‐pressure apparatus. At 12 GPa and 1600°C, all the run products were composed of a single phase with a rutile structure. The lattice constants increase linearly with the germanium content (x), which indicates that the rutile‐type phases in the SiO₂–GeO₂ system form a complete series of solid solutions at these pressure and temperature conditions. Our experimental results show that thermodynamic equilibrium state was achieved in this system at 12 GPa and 1600°C, but not at 1200°C. At lower pressures (7 and 9 GPa) and 1600°C, we observed the decomposition of (Si_0.5,Ge_0.5)O₂ into SiO₂‐rich coesite and GeO₂‐rich rutile phases. The silicon content in the rutile structure increases sharply with pressure in the vicinity of the coesite–stishovite phase transition pressure in SiO₂.     

Effect of MgO/Al2O3 ratio on the crystallization behaviour of Li2O–MgO–Al2O3–SiO2 glass-ceramic and its wettability on Si3N4 ceramic

The composition governs the crystallization ability, the type and content of crystal phases of glass-ceramics. Glass-ceramic joining materials have generated more research interest in recent years. Here, we prepared a novel Li₂O–MgO–Al₂O₃–SiO₂ glass-ceramic for the application of joining Si₃N₄ ceramics. We investigated the influence of the MgO/Al₂O₃ composition ratio on microstructure and crystallization behaviour. The crystallization kinetics demonstrated that the glasses had excellent crystallization ability and high crystallinity. β-LiAlSi₂O₆ and Mg₂SiO₄ were precipitated from the glass-ceramics, and the increase of MgO concentration was conducive to the precipitation of Mg₂SiO₄. Among the glass-ceramic samples, the thermal expansion coefficient of LMAS2 glass-ceramic was 3.1 × 10^?6/°C, which was very close to that of Si₃N₄ ceramics. The wetting test showed that the final contact angle of the glass droplet on the Si₃N₄ ceramic surface was 32° and the interface was well bonded.     

Microstructure and properties of SiCf/SiC composite joints with CaO–Y2O3–Al2O3–SiO2 interlayer

Using CaO, Y₂O₃, Al₂O₃, and SiO₂ micron-powders as raw materials, CaO–Y₂O₃–Al₂O₃–SiO₂ (CYAS) glass was prepared using water cooling method. The coefficient of thermal expansion (CTE) of CYAS glass was found to be 4.3 × 10^?6/K, which was similar to that of SiC_f/SiC composites. The glass transition temperature of CYAS glass was determined to be 723.1 °C. With the increase of temperature, CYAS glass powder exhibited crystallization and sintering behaviors. Below 1300 °C, yttrium disilicate, mullite and cristobalite crystals gradually precipitated out. However, above 1300 °C, the crystals started diminishing, eventually disappearing after heat treatment at 1400 °C. CYAS glass powder was used to join SiC_f/SiC composites. The results showed that the joint gradually densified as brazing temperature increased, while the phase in the interlayer was consistent with that of glass powder heated at the same temperature. The holding time had little effect on phase composition of the joint, while longer holding time was more beneficial to the elimination of residual bubbles in the interlayer and promoted the infiltration of glass solder into SiC_f/SiC composites. The joint brazed at 1400 °C/30 min was dense and defect-free with the highest shear strength of about 57.1 MPa.