Crystal structure and formation mechanism of (Cr2/3Ti1/3)3AlC2 MAX phase

Liu, Zhimou; Wu, Erdong; Wang, Jiemin; Qian, Yuhai; Xiang, Huimin; Li, Xichao; Jin, Qianqian; Sun, Guang; Chen, Xiping; Wang, Jingyang; Li, Meishuan

doi:10.1016/j.actamat.2014.04.006

Cited by 177 publications

(112 citation statements)

References 42 publications

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“…On the contrary, (Ti 1/3 Cr 2/3 ) 3 AlC 2 [38,40] and (V 1/3 Cr 2/3 ) 2 AlC 3 [83] are examples of recent discoveries of chemically ordered quaternary MAX phases, with atomic layers composed of a single element only. Even though they contain Cr, magnetic characteristics have to date only been explored theoretically [39].…”

Section: A Methodsmentioning

confidence: 99%

Magnetic MAX phases from theory and experiments; a review

Ingason

Dahlqvist

Rosén

2016

J. Phys.: Condens. Matter

109

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This review presents MAX phases (M is a transition metal, A an A-group element, X is C or N), known for their unique combination of ceramic/metallic properties, as a recently uncovered family of novel magnetic nanolaminates. The first created magnetic MAX phases were predicted using density functional theory through evaluation of phase stability, and subsequently synthesized as heteroepitaxial thin films. All magnetic MAX phases reported to date, in bulk or thin film form, are based on Cr and/or Mn, and they include (Cr,Mn)2AlC, (Cr,Mn)2GeC, (Cr,Mn)2GaC, (Mo,Mn)2GaC, and (V,Mn)3GaC2, Cr2AlC, Cr2GeC and Mn2GaC. A variety of magnetic properties have been found, such as ferromagnetic response well above room temperature and structural changes linked to magnetic anisotropy. In this paper, theoretical as well as experimental work performed on these materials to date is critically reviewed, in terms of methods used, results acquired, and conclusions drawn. Open questions concerning magnetic characteristics are discussed, and an outlook focused on new materials, superstructures, property tailoring and further synthesis and characterization is presented.

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Section: A Methodsmentioning

confidence: 99%

Magnetic MAX phases from theory and experiments; a review

Ingason

Dahlqvist

Rosén

2016

J. Phys.: Condens. Matter

109

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“…In particular, solid solutions on the M-site include, e.g., (Ti,M)2AlC where M = V, Nb, Ta, Cr, [8][9][10][11] (V,M)2AlC where M = Nb, Ta, Cr, 9,12 (Cr,Mn)2AC where A = Al, Ga, Ge, 3,[13][14][15][16][17][18][19] (Ti,V)3AC2 where A = Al, Ge, 20,21 and (V,M)4AlC3 where M = Ti, Nb. 20,21 Adding a fourth element has also been demonstrated by realization of TiCr2AlC2, 22,23 V1.5Cr1.5AlC2, 12 TiMo2AlC2, 24,25 and Ti2Mo2AlC3, 24 which all are recent discoveries of chemically ordered quaternary MAX phases, with atomic layers composed of a single element only. This raises the question why certain combinations of M elements form layered chemically ordered MAX phases, while other combinations result in a solid solution.…”

Section: Introductionmentioning

confidence: 99%

“…A is kept equal to Al, since i) all chemically ordered MAX phase alloys reported to date include A = Al, 12,[22][23][24][25] i.e. this choice allows theoretical validation of previous experimental results as well as prediction of new alloys, and ii) to date, all known MXenes originate from chemical etching of Al from a MAX phase, 26 with the only exception of Mo2C, 27 i.e.…”

Section: Introductionmentioning

confidence: 99%

Order and disorder in quaternary atomic laminates from first-principles calculations

Dahlqvist

Rosén

2015

Phys. Chem. Chem. Phys.

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We report on the phase stability of chemically ordered and disordered quaternary MAX phases -TiMAlC, TiM2AlC2, MTi2AlC2, and Ti2M2AlC3 where M=Zr,Hf (group IV), M=V,Nb,Ta (group V), and M=Cr,Mo,W (group VI). At 0 K, layered chemically ordered structures are predicted to be stable for M from group V and VI. By taking into account the configurational entropy, an order-disorder temperature Tdisorder can be estimated. TiM2AlC2 (M=Cr,Mo,W) and Ti2M2AlC3 (M=Mo,W) are found with Tdisorder >1773 K and are hence predicted to be ordered at the typical bulk synthesis temperatures of 1773 K. Other ordered phases, even though metastable at elevated temperatures, may be synthesized by non-equilibrium methods such as thin film growth. Furthermore, phases predicted not to be stable in any form at 0 K can be stabilized at higher temperatures in a disordered form, being the case for group IV, for MTi2AlC2 (M=V,Cr,Mo), and for Ti2M2AlC3 (M=V,Ta). The stability of the layered ordered structures with M from group VI can primarily be explained by Ti breaking the energetically unfavorable stacking of M and C where M is surrounded by C in a face-centered cubic configuration, and by M having a larger electronegativity than Al resulting in fewer electrons available for populating antibonding Al-Al orbitals. The results show that these chemically ordered quaternary MAX phases allow for new elemental combinations in MAX phases, which can be used to add new properties to this family of atomic laminates and in turn prospects for tuning these properties.

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“…A reasonable theoretical comparison can be made with the Zr 2 AlC phase, for which no study (theoretical or experimental) of elastic properties exists as well. A compound is considered to be mechanically stable if the single crystal elastic constants C ij are all positive and satisfy the well known Born criteria [31]: C 11 > 0, (C 11 -C 12 ) > 0, C 44 > 0 and (C 11 + C 12 )C 33 > 2 13 2 . The compounds under consideration satisfy these criteria quite well as shown in Table 3 and are therefore, mechanically stable.…”

Section: Elastic Propertiesmentioning

confidence: 99%

Newly synthesized Zr 2 AlC, Zr 2 (Al 0.58 Bi 0.42 )C, Zr 2 (Al 0.2 Sn 0.8 )C, and Zr 2 (Al 0.3 Sb 0.7 )C MAX phases: A DFT based first-principles study

Ali

Hossain

Jahan

et al. 2017

Computational Materials Science

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The structural, elastic, and electronic properties of newly synthesized Zr 2 (Al 0.58 Bi 0.42 )C, Zr 2 (Al 0.2 Sn 0.8 )C, and Zr 2 (Al 0.3 Sb 0.7 )C MAX nanolaminates have been studied using firstprinciples density functional theory (DFT) calculations for the first time. Theoretical Vickers hardness has also been estimated for these compounds. All the calculated results are compared with experimental data and also with that of recently discovered Zr 2 AlC phase, where available. Zr 2 (Al 0.58 Bi 0.42 )C and Zr 2 (Al 0.2 Sn 0.8 )C are the two first Bi and Sn containing MAX compounds. The calculated structural parameters are found to be in good agreement with the experimental data. The single crystal elastic constants C ij and other polycrystalline elastic coefficients have been calculated and the mechanical stabilities of these compounds have been theoretically confirmed. The bulk modulus increases and the shear modulus decreases due to partial Bi/Sn/Sb substitution for Al in Zr 2 AlC. The calculated elastic moduli show that these Bi/Sn/Sb containing MAX phases are more anisotropic than Zr 2 AlC, and have a tendency towards ductility. The Vickers hardness decreases in the Bi/Sn/Sb containing compounds. Further, the electronic band structures and electronic density of states (EDOS) are calculated and the effects of different elemental substitution on these properties are investigated. The electronic band structures show metallic characteristics with contribution predominantly coming from the Zr 4d orbitals. Partial presence of Bi/Sn/Sb atoms increases the EDOS at the Fermi level to some extent. Possible implications of the theoretical results for these recently discovered MAX nanolaminates have been discussed in detail in this paper.

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Crystal structure and formation mechanism of (Cr2/3Ti1/3)3AlC2 MAX phase

Cited by 177 publications

References 42 publications

Magnetic MAX phases from theory and experiments; a review

Magnetic MAX phases from theory and experiments; a review

Order and disorder in quaternary atomic laminates from first-principles calculations

Newly synthesized Zr 2 AlC, Zr 2 (Al 0.58 Bi 0.42 )C, Zr 2 (Al 0.2 Sn 0.8 )C, and Zr 2 (Al 0.3 Sb 0.7 )C MAX phases: A DFT based first-principles study

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