Crystal structure of novel compounds in the systems Zr-Cu-Al, Mo-Pd-Al and partial phase equilibria in the Mo-Pd-Al system
- Autor(en)
- Peter Franz Rogl, Gerald Giester
- Abstrakt
The crystal structures of three Al-rich compounds have been solved from X-ray single crystal diffractometry: tau(1)-MoPd2-xAl8+x (x = 0.067); tau(7)-Zr(Cu1-xAlx)(12)(x = 0.514) and tau(9)-ZrCu1-xAl4 (x = 0.144). tau(1)-MoPd2-xAl8+x adopts a unique structure type (space group Pbcm; lattice parameters a = 0.78153(2), b = 1.02643(3) and c = 0.86098(2) nm), which can be conceived as a superstructure of the Mo(CuxAl1-x)(6)Al-4 type. Whereas Mo-atoms occupy the 4d site, Pd(2) occupies the 4c site, Al and Pd(1) atoms randomly share the 4d position and the rest of the positions are fully occupied by Al. A Barnighausen tree documents the crystallographic group-subgroup relation between the structure types of Mo(CuxAl1-x)(6)Al-4 and tau(1). tau(7)-Zr(Cu1-xAlx)(12) (x = 0.514) has been confirmed to crystallize with the ThMn12 type (space group I4/mmm; lattice parameters a = 0.85243(2) and c = 0.50862(3) nm). In total, 4 crystallographic sites were defined, out of which, Zr occupies site 2a, the 8f site is fully occupied by Cu, the 8i site is entirely occupied by Al, but the 8j site turned out to comprise a random mixture of Cu and Al atoms. The compound tau(9)-ZrCu1-xAl4 (x = 0.144) crystallizes in a unique structure type (space group P4/nmm; lattice parameters a = 0.40275(3) and c = 1.17688(4) nm) which exhibits full atom order but a vacancy (14.4%) on the 2c site, shared with Cu atoms. tau(9)-ZrCu1-xAl4 is a superstructure of Cu with an arrangement of three unit cells of Cu in the direction of the c-axis. A Barnighausen tree documents this relationship. The ZrCu1-xAl4 type (n = 3) is part of a series of structures which follow this building principle: Cu (n = 1), TiAl3 (n = 2), tau(5)-TiNi2-xAl5 (n = 4), HfGa2 (n = 6) and Cu3Pd (n = 7). A partial isothermal section for the Al-rich part of the Mo-Pd-Al system at 860 degrees C has been established with two ternary compounds tau(1)-MoPd2-xAl8+x and tau(2) (unknown structure). The Vickers hardness (H-v) for tau(1) was found to be 842 +/- 40 MPa.
- Organisation(en)
- Institut für Physikalische Chemie, Institut für Mineralogie und Kristallographie
- Journal
- Dalton Transactions
- Band
- 41
- Seiten
- 2296-2303
- Anzahl der Seiten
- 8
- ISSN
- 1477-9226
- DOI
- https://doi.org/10.1039/c1dt11972a
- Publikationsdatum
- 2012
- Peer-reviewed
- Ja
- ÖFOS 2012
- 104017 Physikalische Chemie, 105113 Kristallographie
- Link zum Portal
- https://ucrisportal.univie.ac.at/de/publications/719755f6-3aea-471b-9a3c-daf2983990d0