Decagonal quasicrystal and related crystalline phases in Mn-Ga alloys with 52 to 63 a/o Ga

Abstract

A decagonal quasicrystal (DQC) and six related intermetallic phases with large unit cells have been found in binary Mn-Ga alloys with 52 to 63 at. pct Ga by means of transmission electron microscopy (TEM). As does the Al-Mn DQC, the Ga-Mn DQC also has a periodicity of 1.25 nm along its tenfold axis. However, its Mn content, determined by electron microprobe X-ray analysis (about 45 to 50 at. pct Mn), is much higher than that of the Al-Mn DQC (about 20 to 30 at. pct Mn). The compositions of the intermetallic phases are about 53, 56, 58, and 62 at. pct Ga, corresponding respectively to the unknown structures of MnGa (50.7 to 53.4 at.

Lattice correspondence and fivefold twins of the orthorhombic (2/1, 1/1) and (1/0, 2/1) approximants in a Ga−Fe−Cu−Si alloy

“…As reported earlier by Wu and Kuo, [15] both the Ga-Mn (1/0, 2/1) and (2/1, 1/1) approximants have a B-centered orthorhombic lattice, although with different a and c lattice parameters. In the present study of these two orthorhombic approximants in a Ga-Fe-Cu-Si alloy, their (010) planes are found to consist of different subunits.…”

“…[15] The fivefold twins in the present alloy formed during rapid solidification, as stated in Section I, and appeared in large grains between the fivefold DQC ribbons. [1] In the annealed state, transformation has taken place, and the repeated twins, as well as intersecting twins, are common in both the orthorhombic (1/0, 2/1) and (2/1, 1/1) approximants.…”

Investigation in the Ga-rich side of the Mn–Ga system: Synthesis and crystal structure of MnGa4 and MnGa5−x (x ∼ 0.15)

“…Some of the Mn-Ga binary compounds have been described as quasicrystal approximants. This is precisely the case for orthorhombic Mn3Ga5 and Mn5Ga7, also for Mn5Ga6 (with two closely related orthorhombic cells) and MnGa (two orthorhombic and monoclinic related forms), compounds characterized by means of transmission electron microscopy [19]. Such intermetallic compounds were found to display a pseudo ten-fold distribution of strong diffraction spots and are then considered as crystalline approximants of a quasicrystal containing 45-50 at.…”

Preparation and Crystal Structure of the Pseudo-Decagonal Approximant Mn3Ga5

“…It has won renewed interest due to its close chemical relationship to the Mn}Al system where quasicrystals were "rst discovered (1). A decagonal quasicrystal has also been identi"ed in the Mn}Ga system (2). The large unit cell Mn Ga phase was found by Meissner (3) and co-workers during an investigation of the Mn}Ga binary phase diagram.…”