Modulations in B8-type Intermetallics
(1997)- Abstract
- The B8-type regions of the Mn-Sn and Cu-In systems have been investigated by means of electron and X-ray diffraction. The importance of the combination of these techniques in the study of B8-type phases is pointed out. In addition to the B8-type phases an alloy with a quasicrystal approximant structure has been studied.
In the Mn-Sn system at least three B8-type phases exist. An X-ray powder pattern of the low-temperature phase Mn3Sn2 has been refined with the Rietveld method. The structure of one of the high-temperature phases, Mn8Sn5, has been refined by using the JANA94 program for incommensurate structures, and for the other one, Mn12Sn7, a structural model has been proposed. All three structures are orthorhombic... (More) - The B8-type regions of the Mn-Sn and Cu-In systems have been investigated by means of electron and X-ray diffraction. The importance of the combination of these techniques in the study of B8-type phases is pointed out. In addition to the B8-type phases an alloy with a quasicrystal approximant structure has been studied.
In the Mn-Sn system at least three B8-type phases exist. An X-ray powder pattern of the low-temperature phase Mn3Sn2 has been refined with the Rietveld method. The structure of one of the high-temperature phases, Mn8Sn5, has been refined by using the JANA94 program for incommensurate structures, and for the other one, Mn12Sn7, a structural model has been proposed. All three structures are orthorhombic with different length of the a axis - 2ahex, 5ahex and 7ahex for Mn3Sn2, Mn8Sn5 and Mn12Sn7, respectively, in a commensurate approximation of the phases. ahex refers to the a axis of the base NiAs/Ni2In type cell.
In the Cu-In system at least four B8-type phases, A, B, C and Cu7In3, exist. A fifth phase, Cu11In9, is probably also based on the B8-type structure. The system is very complicated. The A, B and C phases seem to be related through gradual phase transitions. From the monoclinic high-temperature phase A the intermediate phase B is formed by a change in the modulation vector of the A-phase. There are different appearances of the B-phase because of the gradual change in its modulation vector. However, they all resemble each other, and all are closely related to the A-phase. At the end of this transition the C-phase appears as an orthorhombic superstructure with a=9ahex, b=sqrt(3)bhex, c=4chex.
The structure of the quasicrystal approximant (Mg,Na,Al)2(Al,Zn)3 has been refined from single-crystal data. The structure description is made in terms of successive shells of atoms with increasing size. The quasisymmetry of the phase arises from three shells with icosahedral (five-fold) symmetry. The fourth and outermost shell breaks this symmetry and reduces the symmetry to cubic. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/29120
- author
- Elding-Pontén, Margareta LU
- supervisor
- opponent
-
- Dr Landa-Canovas, Angel
- organization
- publishing date
- 1997
- type
- Thesis
- publication status
- published
- subject
- keywords
- Electron diffraction, X-ray diffraction, Superspace group, Edshammar polyhedron, Mn-Sn, Cu-In, B8-type, Ni2In, NiAs, Modulation, Superstructure, Inorganic chemistry, Oorganisk kemi
- pages
- 133 pages
- publisher
- Inorganic Chemistry, Chemical Center, Lund University
- defense location
- Room F, Chemical Center, Lund
- defense date
- 1997-04-11 13:15:00
- external identifiers
-
- other:ISRN: LUTKDH/(TKOO-1018)/1-71/1997
- ISBN
- 91-628-2413-9
- language
- English
- LU publication?
- yes
- additional info
- The information about affiliations in this record was updated in December 2015. The record was previously connected to the following departments: Polymer and Materials Chemistry (LTH) (011001041)
- id
- 17fdab80-5265-47df-a98e-738bca536adf (old id 29120)
- date added to LUP
- 2016-04-04 11:30:25
- date last changed
- 2018-11-21 21:05:16
@phdthesis{17fdab80-5265-47df-a98e-738bca536adf,
abstract = {{The B8-type regions of the Mn-Sn and Cu-In systems have been investigated by means of electron and X-ray diffraction. The importance of the combination of these techniques in the study of B8-type phases is pointed out. In addition to the B8-type phases an alloy with a quasicrystal approximant structure has been studied.<br/><br>
<br/><br>
In the Mn-Sn system at least three B8-type phases exist. An X-ray powder pattern of the low-temperature phase Mn3Sn2 has been refined with the Rietveld method. The structure of one of the high-temperature phases, Mn8Sn5, has been refined by using the JANA94 program for incommensurate structures, and for the other one, Mn12Sn7, a structural model has been proposed. All three structures are orthorhombic with different length of the a axis - 2ahex, 5ahex and 7ahex for Mn3Sn2, Mn8Sn5 and Mn12Sn7, respectively, in a commensurate approximation of the phases. ahex refers to the a axis of the base NiAs/Ni2In type cell.<br/><br>
<br/><br>
In the Cu-In system at least four B8-type phases, A, B, C and Cu7In3, exist. A fifth phase, Cu11In9, is probably also based on the B8-type structure. The system is very complicated. The A, B and C phases seem to be related through gradual phase transitions. From the monoclinic high-temperature phase A the intermediate phase B is formed by a change in the modulation vector of the A-phase. There are different appearances of the B-phase because of the gradual change in its modulation vector. However, they all resemble each other, and all are closely related to the A-phase. At the end of this transition the C-phase appears as an orthorhombic superstructure with a=9ahex, b=sqrt(3)bhex, c=4chex.<br/><br>
<br/><br>
The structure of the quasicrystal approximant (Mg,Na,Al)2(Al,Zn)3 has been refined from single-crystal data. The structure description is made in terms of successive shells of atoms with increasing size. The quasisymmetry of the phase arises from three shells with icosahedral (five-fold) symmetry. The fourth and outermost shell breaks this symmetry and reduces the symmetry to cubic.}},
author = {{Elding-Pontén, Margareta}},
isbn = {{91-628-2413-9}},
keywords = {{Electron diffraction; X-ray diffraction; Superspace group; Edshammar polyhedron; Mn-Sn; Cu-In; B8-type; Ni2In; NiAs; Modulation; Superstructure; Inorganic chemistry; Oorganisk kemi}},
language = {{eng}},
publisher = {{Inorganic Chemistry, Chemical Center, Lund University}},
school = {{Lund University}},
title = {{Modulations in B8-type Intermetallics}},
year = {{1997}},
}