Low temperature densification of silicon nitride using Li2O-based surface coatings

Tatlı, Zafer; Thompson, D. P.

doi:10.1016/j.ceramint.2011.07.067

Cited by 8 publications

(4 citation statements)

References 8 publications

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“…Sintering aids for Si 3 N 4 ceramics include the metallic oxides of Al 2 O 3 [10], MgO [11], Li 2 O [12], and CaO [13], as well as rare earth oxides like Y 2 O 3 [14], Yb 2 O 3 [15], and Lu 2 O 3 [16], forming binary aids through the combination of their compounds. Initially, the earliest sintering aid was MgO.…”

Section: Introductionmentioning

confidence: 99%

A Study on the Effects of Liquid Phase Formation Temperature and the Content of Sintering Aids on the Sintering of Silicon Nitride Ceramics

Huang

et al. 2023

Crystals

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Due to its high bonding energy and low self-diffusion coefficient, silicon nitride (Si3N4) ceramics cannot form a dense structure with prolonged high-temperature insulation or by raising the sintering temperature. To improve the density of the sintered Si3N4 ceramics, additives are added to promote the rearrangement–dissolution–precipitation process of the crystal grains. However, the liquid phase formation temperature of different sintering aid chemical compositions varies, making it challenging to isolate the mechanism and the effect of liquid phase formation temperatures on sintering. Hence, we developed three sintering aids, namely Y2O3-Al2O3 (YA), Y2Si2O7 (Y2S), and Y2Si2O7-Al6Si2O13 (Y2SM), with homologous elements and different liquid phase formation temperatures. These sintering aids can form a liquid phase with SiO2 on the surface of Si3N4 at varying temperatures. We analyzed the sintered Si3N4 ceramic’s density, volume shrinkage rate, and microstructure to verify the YA’s lower liquid phase formation temperature effect, providing more rearrangement time and increasing sintering density. Conversely, sintering aids with too low liquid phase formation temperatures are more prone to volatilize during high-temperature sintering stages, thereby reducing sintering density. This research found that different liquid phase formation temperatures do not affect the α→β phase transition temperature of Si3N4 ceramics. We also evaluated the Y2S sintering aid contents’ effect on Si3N4 ceramics sintering. The results revealed that aiding sintering with too little Y2S content is insufficient for liquid phase production, and hence does not improve sintering density. Conversely, excessive liquid phase can improve density and refine grain size but increases weight loss rate during sintering due to volatilization.

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Section: Introductionmentioning

confidence: 99%

A Study on the Effects of Liquid Phase Formation Temperature and the Content of Sintering Aids on the Sintering of Silicon Nitride Ceramics

Huang

et al. 2023

Crystals

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“…However, the impurities were left due to the incomplete reaction with each other, which seriously affected dielectric properties of materials. Recently, some reports utilized the characterization of rapid volatilization of Li 2 O sintering additives at high temperature to reduce sintering additives residues [32][33][34], which might be beneficial for the fabrication of the pure porous Si 2 N 2 O ceramics.…”

Section: Introductionmentioning

confidence: 99%

Fabrication and properties of Si2N2O ceramics for microwave sintering furnace

Fan

Zhang

et al. 2020

PAC

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The Si 2 N 2 O ceramics with low dielectric constant, low thermal diffusivity and high thermal shock resistance were successfully prepared by vacuum sintering. The amorphous Si 3 N 4 was used as raw material with Li 2 CO 3 as sintering additive. The phase, microstructure, oxidized resistance, mechanical and dielectric properties of the Si 2 N 2 O ceramics were investigated. XRD analysis showed that the suitable content of Li 2 CO 3 could promote the generation of Si 2 N 2 O ceramics. However, the excess or insufficient amount of Li 2 CO 3 additive would cause decomposition of Si 2 N 2 O phase. The Li 2 O volatilized at high temperature leaving highly pure (99.63%) porous Si 2 N 2 O ceramics. The flexural strength of the porous Si 2 N 2 O ceramics (with ≈49.19% of open porosity) was about 30 MPa, the residual strength ratio was more than 70% after 1300°C quenching in air. The SiO 2 layer formed by oxidization could prevent Si 2 N 2 O ceramics from further oxidizing. Therefore, these Si 2 N 2 O ceramics will be excellent thermal insulation and wave-transparent materials for high temperature microwave sintering furnace.

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“…In the present work, the porous β‐Si 3 N 4 ceramics were prepared by low‐temperature sintering and postvacuum heat treatment (VHT) using a small amount of Li 2 O and Y 2 O 3 as sintering additives. Li 2 O and Li 2 O–Y 2 O 3 have been researched as sintering additives for low‐temperature sintering of dense Si 3 N 4 . However, it is hard to complete the final densification for dense Si 3 N 4 ceramics using these sintering additives, arising from the rapid volatilization of Li 2 O above 1300°C from the powder compact .…”

Section: Introductionmentioning

confidence: 99%

“…Li 2 O and Li 2 O–Y 2 O 3 have been researched as sintering additives for low‐temperature sintering of dense Si 3 N 4 . However, it is hard to complete the final densification for dense Si 3 N 4 ceramics using these sintering additives, arising from the rapid volatilization of Li 2 O above 1300°C from the powder compact . This characteristic of Li 2 O is, conversely, beneficial for the fabrication of porous Si 3 N 4 ceramics.…”

Section: Introductionmentioning

confidence: 99%

Low‐Temperature Preparation of β‐Si₃N₄ Porous Ceramics with a Small Amount of Li₂O–Y₂O₃

et al. 2014

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Porous β‐Si3N4 ceramics are sintered at 1600°C in N2 and postheat treated at 1500°C under vacuum using Li2O and Y2O3 as the sintering additives. The partial sintering and phase transformation are promoted at low temperature by the addition of Li2O. The addition of Y2O3 is advantageous for the formation of high aspect ratio β‐Si3N4 grains. After postheat treatment, a large amount of intergranular glassy phase is removed, and the Li content in the samples is decreased. By this method, the β‐Si3N4 porous ceramic with a porosity of 54.1% and high flexural strength of 110 ± 8.1 MPa can be prepared with a small amount of sintering additives, 0.66 wt% Li2O and 0.33 wt% Y2O3, and it is suitable for high‐temperature applications.

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Low temperature densification of silicon nitride using Li2O-based surface coatings

Cited by 8 publications

References 8 publications

A Study on the Effects of Liquid Phase Formation Temperature and the Content of Sintering Aids on the Sintering of Silicon Nitride Ceramics

A Study on the Effects of Liquid Phase Formation Temperature and the Content of Sintering Aids on the Sintering of Silicon Nitride Ceramics

Fabrication and properties of Si2N2O ceramics for microwave sintering furnace

Low‐Temperature Preparation of β‐Si₃N₄ Porous Ceramics with a Small Amount of Li₂O–Y₂O₃

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Low temperature densification of silicon nitride using Li2O-based surface coatings

Cited by 8 publications

References 8 publications

A Study on the Effects of Liquid Phase Formation Temperature and the Content of Sintering Aids on the Sintering of Silicon Nitride Ceramics

A Study on the Effects of Liquid Phase Formation Temperature and the Content of Sintering Aids on the Sintering of Silicon Nitride Ceramics

Fabrication and properties of Si2N2O ceramics for microwave sintering furnace

Low‐Temperature Preparation of β‐Si3N4 Porous Ceramics with a Small Amount of Li2O–Y2O3

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Low‐Temperature Preparation of β‐Si₃N₄ Porous Ceramics with a Small Amount of Li₂O–Y₂O₃