High-Resolution Transmission Electron Microscopy of Ti4AlN3, or Ti3Al2N2 Revisited |
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| Authors: | Michel W. Barsoum Leonid Farber Igor Levin Adam Procopio Tamer El-Raghy Alex Berner |
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| Affiliation: | Department of Materials Engineering, Drexel University, Philadelphia, Pennsylvania 19104,;Ceramics Division, National Institute of Standards and Technology (NIST), Gaithersburg, Maryland 20899,;and Technion—Israel Institute of Technology, Haifa, Israel |
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| Abstract: | The structure and chemistry of what initially was proposed to be Ti3Al2N2 are incorrect. Using high-resolution transmission electron microscopy, together with chemical analysis, the stoichiometry of this compound is concluded to be Ti4AlN3-delta (where delta = 0.1). The structure is layered, wherein every four layers of almost-close-packed Ti atoms are separated by a layer of Al atoms. The N atoms occupy ∼97.5% of the octahedral sites between the Ti atoms. The unit cell is comprised of eight layers of Ti atoms and two layers of Al atoms; the unit cell is hexagonal with P 63/ mmc symmetry (lattice parameters of a = 0.3 nm and c = 2.33 nm). This compound is machinable and closely related to other layered, ternary, machinable, hexagonal nitrides and carbides, namely M2AX and M3AX2 (where M is an early transition metal, A is an A-group element, and X is carbon and/or nitrogen). |
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