MAX phases
Definition
The MAX phases are layered, hexagonal carbides and nitrides have the general formula: Mn+1AXn, (MAX) where n = 1 to 3, M is an early transition metal, A is an A-group (mostly IIIA and IVA, or groups 13 and 14) element and X is either carbon and/or nitrogen. The layered structure consists of edge-sharing, distorted XM6 octahedra interleaved by single planar layers of the A-group element.
For more information check the following link :
https://en.wikipedia.org/wiki/MAX_phases
Crystal structure
The max phase compounds occured in 2 structures: hexagonal (P63/mmc) and cubic (Fm3m).
Hexagonal structure
Example: Ti3AlC2
The space group: P63/mmc
The MAX solid solutions (Zr3-xTix)AlC2 crystallize in the hexagonal structure in the space group P63/ mmc (No. 194) [49, 50]. The transition metal atoms M(1) and M(2) occupy the Wyckoff positions 2a and 4f (zM * 0.12), respectively. The Al atoms reside in 2b atomic sites. The C atoms take up the 4f (zM * 0.07) atomic positions with different z-values. The unit cell of 312 MAX phases consists of two formula units (Check the Fig. ).
Reference: https://core.ac.uk/download/pdf/81919665.pdf
The MAX phases are layered, hexagonal carbides and nitrides have the general formula: Mn+1AXn, (MAX) where n = 1 to 3, M is an early transition metal, A is an A-group (mostly IIIA and IVA, or groups 13 and 14) element and X is either carbon and/or nitrogen. The layered structure consists of edge-sharing, distorted XM6 octahedra interleaved by single planar layers of the A-group element.
For more information check the following link :
https://en.wikipedia.org/wiki/MAX_phases
| 211 Phases | 312 Phases | 413 Phases |
|---|---|---|
| Ti2CdC, Sc2InC, Ti2AlC, Ti2GaC, Ti2InC, Ti2TlC, V2AlC, V2GaC, Cr2GaC, Ti2AlN, Ti2GaN, Ti2InN, V2GaN, Cr2GaN, Ti2GeC, Ti2SnC, Ti2PbC, V2GeC, Cr2AlC, Cr2GeC, V2PC, V2AsC, Ti2SC, Zr2InC, Zr2TlC, Nb2AlC, Nb2GaC, Nb2InC, Mo2GaC, Zr2InN, Zr2TlN, Zr2SnC, Zr2PbC, Nb2SnC, Nb2PC, Nb2AsC, Zr2SC, Nb2SC, Hf2InC, Hf2TlC, Ta2AlC, Ta2GaC, Hf2SnC, Hf2PbC, Hf2SnN, Hf2SC, Zr2AlC | Ti3AlC2, Ti3GaC2,
Ti3InC2, V3AlC2,
Ti3SiC2, Ti3GeC2, Ti3SnC2, Ta3AlC2,
Zr3AlC2
| Ti4AlN3,
V4AlC3,
Ti4GaC3, Ti4SiC3, Ti4GeC3, Nb4AlC3, Ta4AlC3, |
Crystal structure
The max phase compounds occured in 2 structures: hexagonal (P63/mmc) and cubic (Fm3m).
Hexagonal structure
Example: Ti3AlC2
The space group: P63/mmc
Wyckoff Positions of Group 194 (P63/mmc)
The MAX solid solutions (Zr3-xTix)AlC2 crystallize in the hexagonal structure in the space group P63/ mmc (No. 194) [49, 50]. The transition metal atoms M(1) and M(2) occupy the Wyckoff positions 2a and 4f (zM * 0.12), respectively. The Al atoms reside in 2b atomic sites. The C atoms take up the 4f (zM * 0.07) atomic positions with different z-values. The unit cell of 312 MAX phases consists of two formula units (Check the Fig. ).
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