Phases and twinning in C2Al3B48 (beta AlB12)
Abstract
The aluminum-boron phase described recently as beta AlB12 is shown to consist of two crystallographically related, intergrown phases with the bulk stoichiometry of C2Al3B48. One phase (A) is orthorhombic with a = 12.34 Å, b = 12.63 Å and c = 5.08 Å and space group Cmma or C2ma. The other phase (B) is also orthorhombic with a = 6.17 Å, b = 12.63 Å and c = 10.16 Å and space group Ammm, A222 or A2mm.
Twinning is always present and occurs across the (110) and (1[unk]0) faces. Occasionally an unusual type of twinning appears in which the a and b axes of both phases are parallel. This is interpreted as evidence of a disproportionation from a single high-temperature phase. This has been verified experimentally. The high-temperature phase (C) is tetragonal with a = 8.82 Å, c = 5.09 Å and space group P4/nmm, P4/n or P42/n. The transformation, which is reversible, is gradual and complete at about 850°C.
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Artikel in diesem Heft
- Die Kristallstruktur von bis-Cyclooctadien-(1,5)-Nickel(0)
- Corrections for x-ray absorption by a crystal of arbitrary shape1
- Kristall- und Molekülstruktur von bis-Methallylnickel Ni[(CH2)2C · CH3]2
- A preliminary orienting procedure for single crystals, using the Weissenberg camera
- Mg2+ – Fe2+ order in an orthopyroxene, Mg0.93Fe1.07Si2O6
- On the x-ray determination of the iron-magnesium ratio in biotites
- Phases and twinning in C2Al3B48 (beta AlB12)
- Packing of B12 groups in boron and boride structures
- A crystallographic study of ammonium and rubidium imidodisulphates
- Interstitial derivatives of β boron
- Die Intensität der an gebogenen Glimmerspaltflächen in höheren Ordnungen reflektierten Röntgenstrahlung
- Morphology and space group of hexaantipyrine perchlorate complexes of Mg++, Ca++ and Zn++, and pentaantipyrine perchlorate of Cu++
- Kristallographische Daten von Quecksilber(I)-acetat
- Preliminary x-ray crystallographic data for 3,7-dideoxy-7-iodo-heptulosonate methyl ester
