Crystal structures of cobalt aluminum silicide, Co19+xAl43+ySi12-y (x = -0.14, y = 0.14; x = 0.49, y = -0.49), the ϒ phase in the Co-Al-Si system

Richter, Klaus W.; Prots, Yu.

doi:10.1524/ncrs.2006.0004

Cited by 2 publications

(2 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It consists of large grains of the " phase showing strong polarization effects. A few isolated small grains of the neighboring ' phase Co 10+x Al 23Àx Si 9À2x (Richter & Prots, 2006b) were also identified in the sample.…”

Section: Resultsmentioning

confidence: 91%

Crystal structure and local order in Co₆Al_11−xSi_6+x

Richter¹,

Prots²,

Borrmann³

et al. 2007

Acta Crystallogr Sect B

View full text Add to dashboard Cite

The ternary compound Co(6)Al(11-x)Si(6+x) (epsilon phase) was prepared from the elements by arc melting and subsequent heat treatment, and then characterized by single-crystal X-ray diffraction (XRD), electron-probe microanalysis (EPMA), differential thermal analysis (DTA) and transmission electron microscopy (TEM). This new structure type consists of planar layers with the composition [Co(6)Al(10)Si(4)], which are penetrated by perpendicular (Si-Si-Al) chains. While the layers are well described by an orthorhombic model (space group Pnma, Pearson symbol oP46), the chains exhibit doubled periodicity, thus yielding a superstructure. Two alternative ordering models (space group Cmc2(1), oC184, and space group P2(1)/c, mP92) are presented and discussed based on XRD and TEM results. The (Si-Si-Al) chains are located in pentagonal antiprismatic ;channels' which reveal the similarity of the Co(6)Al(11-x)Si(6+x) structure to Al-rich transition-metal compounds such as Co(4)Al(13), Co(2)Al(5), Fe(4)Al(13), V(7)Al(45), V(4)Al(23) and VAl(10), which also exhibit this type of pentagonal ;channels' in their crystal structures. The phase shows only a very small homogeneity range.

show abstract

Section: Resultsmentioning

confidence: 91%

Crystal structure and local order in Co₆Al_11−xSi_6+x

Richter¹,

Prots²,

Borrmann³

et al. 2007

Acta Crystallogr Sect B

View full text Add to dashboard Cite

show abstract

“…The TM−Al−Si systems (TM = Fe, Co) have been the focus of intense study. In addition to Fe 25 Al 78 Si 20 , distinct crystal structures have been reported for compounds with compositions near Fe 45 Al 168 Al 24 , 9 Fe 2 Al 9 Si 2 , 10 FeAl 3 Si 2 , 11 FeAl 2.7 Si 2.3 , 11 FeAl 2 Si, 12 Fe 1.7 Al 4 Si, 13 Fe 2 Al 3 Si 3 , 14 Fe 3 Al 2 Si 3 , 15 Fe 3 Al 2 Si 4 , 15a Fe 2 Al 3 Si, 15b Co 3 Al 3 Si 4 , 16 Co 4 Al 8 Si, 17 Co 2 AlSi 2 , 16 Co 19 Al 43 Si 12 , 18 and Co 5 (Al/Si) 16 . 18b, 19 As could be guessed from this impressive list of structures, the phase diagrams for these ternary systems are complicated, and many of their details 17 it exhibits an incommensurately modulated structure, which will be described in a future publication.…”

Section: ■ Introductionmentioning

confidence: 99%

Fragmentation of the Fluorite Type in Fe₈Al_17.4Si_7.6: Structural Complexity in Intermetallics Dictated by the 18 Electron Rule

Fredrickson

2012

Inorg. Chem.

View full text Add to dashboard Cite

This Article presents the synthesis, structure determination, and bonding analysis of Fe(8)Al(17.4)Si(7.6). Fe(8)Al(17.4)Si(7.6) crystallizes in a new monoclinic structure type based on columns of the fluorite (CaF(2)) structure type. As such, the compound can be seen as part of a structural series in which the fluorite structure-adopted by several transition metal disilicides (TMSi(2))-is fragmented by the incorporation of Al. Electronic structure analysis using density functional theory (DFT) and DFT-calibrated Hückel calculations indicates that the fluorite-type TMSi(2) phases (TM = Co, Ni) exhibit density of states (DOS) pseudogaps near their Fermi energies. An analogous pseudogap occurs for Fe(8)Al(17.4)Si(7.6), revealing that its complex structure serves to preserve this stabilizing feature of the electronic structure. Pursuing the origins of these pseudogaps leads to a simple picture: the DOS minimum in the TMSi(2) structures arises via a bonding scheme analogous to those of 18 electron transition metal complexes. Replacement of Si with Al leads to the necessity of increasing the (Si/Al):TM ratio to maintain this valence electron concentration. The excess Si/Al atoms are accommodated through the fragmentation of the fluorite type. The resulting picture highlights how the elucidating power of bonding concepts from transition metal complexes can extend into the intermetallic realm.

show abstract

Crystal structures of cobalt aluminum silicide, Co19+xAl43+ySi12-y (x = -0.14, y = 0.14; x = 0.49, y = -0.49), the ϒ phase in the Co-Al-Si system

Cited by 2 publications

References 7 publications

Crystal structure and local order in Co₆Al_11−xSi_6+x

Crystal structure and local order in Co₆Al_11−xSi_6+x

Fragmentation of the Fluorite Type in Fe₈Al_17.4Si_7.6: Structural Complexity in Intermetallics Dictated by the 18 Electron Rule

Contact Info

Product

Resources

About

Crystal structures of cobalt aluminum silicide, Co19+xAl43+ySi12-y (x = -0.14, y = 0.14; x = 0.49, y = -0.49), the ϒ phase in the Co-Al-Si system

Cited by 2 publications

References 7 publications

Crystal structure and local order in Co6Al11−x Si6+x

Crystal structure and local order in Co6Al11−x Si6+x

Fragmentation of the Fluorite Type in Fe8Al17.4Si7.6: Structural Complexity in Intermetallics Dictated by the 18 Electron Rule

Contact Info

Product

Resources

About

Crystal structure and local order in Co₆Al_11−xSi_6+x

Crystal structure and local order in Co₆Al_11−xSi_6+x

Fragmentation of the Fluorite Type in Fe₈Al_17.4Si_7.6: Structural Complexity in Intermetallics Dictated by the 18 Electron Rule