The Structural Characterisation of Sialon Polytypoids

Thompson, D. P.; Korgul, P.; Hendry, A.

doi:10.1007/978-94-009-6851-6_4

Cited by 25 publications

(11 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…30,31 There are SiAlON polytype phases that are ordered based on the wurtzite structure of AlN. 32 It is conceivable that many glassy phases in the intergranular thin films can have compositions and local bonding similar to SiAlON solid solutions.…”

Section: Introductionmentioning

confidence: 99%

Electronic Structure and Bonding of β‐SiAlON

Ching

Huang

2000

Journal of the American Ceramic Society

View full text Add to dashboard Cite

The ␣-and ␤-SiAlONs are ceramic solid solutions with charge-neutral substitutions in ␣-and ␤-Si 3 N 4 . They have high potential for applications as structural materials. We have calculated the electronic structure and bonding of ␤-Si 6 -z Al z O z N 8 -z for z ‫؍‬ 0, 1, 2, 3, 4 using a first-principles method. Total energy calculations show that the bulk modulus of ␤-Si 6 -zAl z O z N 8 -z decreases as z increases, in general agreement with experimental trends. Simultaneous substitution of the (Si,N) pair by (Al,O) results in impurity-like states in the upper portion of the bandgap of ␤-Si 3 N 4 . As z increases, more and more states are introduced into the gap, forming a new conduction band (CB) edge for SiAlON. At z ‫؍‬ 4, the calculated bandgap is ϳ1.3 eV. Density of states (DOS) calculations show the top of the valence band remains steep for all z, and the bottom of the CB is formed predominately by Si-O antibonding states. Orbitally resolved partial DOS calculations in the CB region are used to predict the trends of the electron-energy-loss near-edge spectra (ELNES) of Si-L 2,3 , Al-L 2,3 , Si-K, Al-K, O-K, and N-K edges in ␤-SiAlON. The impurity-like states near the CB edge result in pre-edge structures in all ELNES spectra. Effective charge and bond order calculations show that the overall bond strength in ␤-SiAlON decreases only slightly as z increases. Although the stronger Si-N bonds are replaced by weaker Al-O bonds, the remaining Si-N and Al-O bonds actually strengthen as z increases because of the effective charge redistribution after substitution. This is a very interesting finding that may partly explain the superior mechanical properties of the SiAlON system that render them suitable for structural applications.

show abstract

Section: Introductionmentioning

confidence: 99%

Electronic Structure and Bonding of β‐SiAlON

Ching

Huang

2000

Journal of the American Ceramic Society

View full text Add to dashboard Cite

show abstract

“…2(e) and (f)), which will be referred to as 12H′ due to the incorporation of the Sc cation. It has been found that the cations with smaller ionic radii, like Li + , Be + , and Mg 2+ , can also be incorporated into tetrahedral or octahedral sites in the structures of the AlN‐polytypoid phases 13,19 …”

Section: Resultsmentioning

confidence: 99%

“…It has been found that the cations with smaller ionic radii, like Li 1 , Be 1 , and Mg 21 , can also be incorporated into tetrahedral or octahedral sites in the structures of the AlN-polytypoid phases. 13,19 The typical TEM microstructure of ScLu1010E2 is shown in Fig. 3(a).…”

Section: Resultsmentioning

confidence: 99%

Sc³⁺–Lu³⁺‐Doped α‐SiAlONs

Liu

et al. 2007

Journal of the American Ceramic Society

View full text Add to dashboard Cite

Sc3+ and dual Sc3+–Lu3+‐doped α‐SiAlON compositions were sintered by hot pressing, and the formation behavior, microstructure, and mechanical properties were assessed. It was found that the small cation Sc3+ could not be accommodated into the α‐SiAlON structure alone. The addition of Lu2O3 in the composition induces the Sc3+ cation to enter the α‐SiAlON structure, and leads to the production of α‐SiAlON with an elongated‐grain microstructure. Transmission electron microscopy analysis shows that α‐SiAlON grains always contain an α‐Si3N4 core, implicating heterogeneous nucleation to be in present in a mixed lutetium/scandium‐doped α‐SiAlON system.

show abstract

“…10,19,52,53 It has been reported that in the AlN polytypoid crystal structure, tetrahedral and octahedral sites can easily accommodate cations with small ionic radii (such as Mg +2 , Li + , and Sc +3 ). [53][54][55] Furthermore, it has been reported that the formation of magnesiumdoped AlN polytypoid starts to take place at about 1400 • C, which is slightly higher than the MgSiAlON eutectic temperature. 27 Thus, in the present study, the formation of a high amount of magnesium-rich eutectic liquid (with the increase in x value) is believed to be consumed by Mg containing 12H′ polytype.…”

Section: Effect Of Magnesium-rich Aluminum Nitride Polytypementioning

confidence: 99%

Synthesis of Mg‐stabilized nitrogen‐rich alpha‐sialons along Si₃N₄–0.5Mg₃N₂:3AlN line via field‐assisted sintering

2022

View full text Add to dashboard Cite

The present study reports for the first time the synthesis and evaluation of magnesium (Mg)‐doped nitrogen‐rich (N‐rich) sialon ceramics exploring the possible existence of Mg‐stabilized single‐phase alpha‐sialon (on the Mg‐alpha‐sialon plane). Mg‐stabilized N‐rich sialons, with the general formula of MgxSi12−2xAl2xN16 having x value in the range of 0.2–2.2 for the composition laying along the Si3N4–0.5Mg3N2:3AlN line, were synthesized at 1500°C, using nano‐size starting powder precursors and field‐assisted (or spark plasma) sintering technique. Consolidated sialon ceramic samples were characterized for their microstructure, phase stability regime, and physical and mechanical properties. Although a relatively low synthesis temperature was adopted, well densified sialon samples were achieved; however, the densification of the samples became difficult with a higher x value (containing high Mg3N2/AlN content). Contrary to what was expected to take place, a single‐phase Mg‐doped sialon was not obtained near the N‐rich line (on Mg‐alpha‐sialon plane). Such distinctive behavior in Mg‐doped sialons was supposed to be due to the formation of a highly stable Mg‐containing aluminum nitride polytype phase, which consumed most of the high‐temperature transient liquid phase. Mg‐doped N‐rich sialon sample having the maximum amount of alpha phase depicted a remarkable hardness (HV10) of 21.4 GPa and a fracture toughness of 3.5 MPa m1/2.

show abstract

The Structural Characterisation of Sialon Polytypoids

Cited by 25 publications

References 17 publications

Electronic Structure and Bonding of β‐SiAlON

Electronic Structure and Bonding of β‐SiAlON

Sc³⁺–Lu³⁺‐Doped α‐SiAlONs

Synthesis of Mg‐stabilized nitrogen‐rich alpha‐sialons along Si₃N₄–0.5Mg₃N₂:3AlN line via field‐assisted sintering

Contact Info

Product

Resources

About

The Structural Characterisation of Sialon Polytypoids

Cited by 25 publications

References 17 publications

Electronic Structure and Bonding of β‐SiAlON

Electronic Structure and Bonding of β‐SiAlON

Sc3+–Lu3+‐Doped α‐SiAlONs

Synthesis of Mg‐stabilized nitrogen‐rich alpha‐sialons along Si3N4–0.5Mg3N2:3AlN line via field‐assisted sintering

Contact Info

Product

Resources

About

Sc³⁺–Lu³⁺‐Doped α‐SiAlONs

Synthesis of Mg‐stabilized nitrogen‐rich alpha‐sialons along Si₃N₄–0.5Mg₃N₂:3AlN line via field‐assisted sintering