Phase equilibria in the system Y2O3-Al2O3-SiO2

Bondar, I. A.; Galakhov, F. Ya.

doi:10.1007/bf00863139

Cited by 28 publications

(11 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“… Liquidus surface for the ternary system Y 2 O 3 /Al 2 O 3 /SiO 2 . Adapted from the diagram of Bonder and Galakhov 38 . Regions of approximate grain boundary compositions determined by STEM/EDX are marked as: (a) Al 2 O 3 –5% SiC–0.15% Y 2 O 3 , (b) Al 2 O 3 –5% SiC, (c) Al 2 O 3 –0.15% Y 2 O 3 .…”

Section: Discussionsupporting

confidence: 91%

“…The lowest eutectic point (point 8 in Fig. 9) is at 1345°C, at composition 22 wt% Al 2 O 3 , 32 wt% Y 2 O 3 , and 46 wt% SiO 2 38 . Thus, if silica were present, either as a pre‐existing surface layer on the SiC particles, or by their partial oxidation during sintering, a liquid grain boundary film could possibly be formed, providing a means of enhancing sintering.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Effects of Yttrium on the Sintering and Microstructure of Alumina–Silicon Carbide “Nanocomposites”

Cock

Shapiro

Todd

et al. 2005

Journal of the American Ceramic Society

View full text Add to dashboard Cite

Alumina and alumina-based ''nanocomposites'' with 2 and 5 vol% silicon carbide and varying amounts of yttria (0-1.5 wt%) have been prepared by pressureless sintering in the temperature range 14501-16501C. The effects of composition and sintering temperature on density and microstructure are reported. Yttria inhibited sintering in alumina, but enhanced the sinterability of the nanocomposites. It also induced abnormal grain growth in both alumina and nanocomposites, but strongly bimodal grain size distributions could be prevented by careful choice of the composition and the sintering temperature. Fully dense (499%), fine-grained alumina-5 vol% SiC-1.5 wt% yttria nanocomposites were produced from uniaxially pressed powders with a yttria content of 1.5 wt% and a sintering temperature of 16001C. Reasons for this behavior are discussed, and it is suggested that the enhancement of sintering in the alumina-SiC materials is because of the reaction of silica on the surface of the silicon carbide particles with alumina, yttria, and possibly magnesia, modifying the grain boundary composition, resulting in enhanced grain boundary diffusion. scanning transmission electron microscopy/energy-dispersive X-ray data show that such cosegregation does occur in the yttria-containing nanocomposites.

show abstract

Section: Discussionsupporting

confidence: 91%

Section: Discussionmentioning

confidence: 99%

Effects of Yttrium on the Sintering and Microstructure of Alumina–Silicon Carbide “Nanocomposites”

Cock

Shapiro

Todd

et al. 2005

Journal of the American Ceramic Society

View full text Add to dashboard Cite

show abstract

“…The composition and melting point of secondary phases seem to be in good agreement with predictions made from the Al 2 O 3 /Y 2 O 3 /SiO 2 phase diagram 22,23,25–27 . The compositions of the secondary phases detected surround the quasi‐ternary eutectic, which melts at 1660 K (Fig.…”

Section: Discussionsupporting

confidence: 83%

“…The presence of both thermal and dilatometric effects at 1660 K can be interpreted based on the ternary phase diagram Al 2 O 3 –Y 2 O 3 –SiO 2 . Indeed, this temperature range corresponds to the eutectic valley in the phase diagram, 21–23 which exhibits an eutectic composition that melts at around 1658 K.…”

Section: Resultsmentioning

confidence: 99%

Effect of Silica on the Reactive Sintering of Polycrystalline Nd:YAG Ceramics

Maı̂tre

Sallé

Boulesteix

et al. 2008

Journal of the American Ceramic Society

View full text Add to dashboard Cite

In the present work, the role of silica as sintering aids in the densification and the grain growth of yttrium aluminum garnet doped by neodymium (Nd:YAG) ceramics has been investigated. The samples were prepared by ball milling of pure oxides (Al2O3, Y2O3, Nd2O3, SiO2), shaped by cold uniaxial pressing, and sintered in vacuum between 1473 and 1973 K. After cooling, the specimens were annealed under air or vacuum. Their microstructure and the chemical composition of the secondary phases were examined using electron probe microanalysis, scanning electron microscopy, or transmission electron microscopy techniques. From these results, silica addition proved to be efficient on the densification kinetics between 1673 and 1873 K, especially when SiO2 content exceeds 0.05 wt%. Indeed, the solid‐state reaction between SiO2 and Nd:YAG particles in the vicinity of 1660 K leads to a liquid phase that adopts a eutectic composition in the Al2O3–Y2O3–SiO2 system. This phase enhances the densification by improving rearrangement of particles and mass transport at the grain boundaries. At a high temperature, liquid phase and silica were partially removed and some intergranular and intragranular inclusions of residual silica remained after cooling. The most promising thermal treatment consists of sintering Nd:YAG ceramics under vacuum at a high temperature (T≥1973 K) to reach fully dense pieces and to decrease the volume fraction of secondary phases (i.e., liquid phase or silica‐based phases). Finally, these conditions would allow to produce transparent YAG pieces due to their good homogeneity with regard to their microstructural properties (grain size, volume fraction of secondary phases).

show abstract

“…Al 2 O 3 and Y 2 O 3 are common sintering additives since they can react with SiO 2 , a native oxide of SiC powders, to form a eutectic liquid phase in the Al 2 O 3 –Y 2 O 3 –SiO 2 ternary system and because they promote densification of SiC by liquid‐phase sintering. The addition of CaO, in addition to Al 2 O 3 –Y 2 O 3 , should reduce the eutectic temperature of the system since the lowest eutectic temperature in the Al 2 O 3 –CaO–SiO 2 system is 1170°C, which is lower than the lowest eutectic temperature (1350°C) in the Al 2 O 3 –Y 2 O 3 –SiO 2 system . Actually, the postannealing of the hot‐pressed SiC ceramics with Al 2 O 3 –Y 2 O 3 –CaO in previous works led to the occurrence of an appreciable β→α phase transformation of SiC at temperatures as low as 1800°C, resulting in a toughened microstructure.…”

Section: Resultsmentioning

confidence: 99%

Mechanical and Thermal Properties of Pressureless Sintered Silicon Carbide Ceramics with Alumina–Yttria–Calcia

2016

View full text Add to dashboard Cite

The effect of sintering temperature on the mechanical and thermal properties of SiC ceramics sintered with Al 2 O 3 -Y 2 O 3 -CaO without applied pressure was investigated. SiC ceramics containing A 2 O 3 -Y 2 O 3 -CaO as sintering additives can be sintered to >97% theoretical density at temperatures between 1750°C and 1900°C without applied pressure. A toughened microstructure, consisting of relatively large elongated grains and relatively small equiaxed grains, has been obtained when sintered at temperatures as low as 1800°C for 2 h in an argon atmosphere without applied pressure. The achievement of toughened microstructures under such mild conditions is the result of the additive composition. The thermal conductivity of the SiC ceramics increased with increasing sintering temperature because of the decrease in the lattice oxygen content of the SiC grains. Typical sintered density, flexural strength, fracture toughness, hardness, and thermal conductivity of the 1850°C-sintered SiC, which consisted of 62.2% 4H, 35.7% 6H, and 2.1% 3C, were 99.0%, 628 MPa, 5.3 MPaÁm 1/2 , 29.1 GPa, and 80 WÁ(mÁK) -1 , respectively.

show abstract

Phase equilibria in the system Y2O3-Al2O3-SiO2

Cited by 28 publications

References 0 publications

Effects of Yttrium on the Sintering and Microstructure of Alumina–Silicon Carbide “Nanocomposites”

Effects of Yttrium on the Sintering and Microstructure of Alumina–Silicon Carbide “Nanocomposites”

Effect of Silica on the Reactive Sintering of Polycrystalline Nd:YAG Ceramics

Mechanical and Thermal Properties of Pressureless Sintered Silicon Carbide Ceramics with Alumina–Yttria–Calcia

Contact Info

Product

Resources

About