Electronic structures, elastic properties, and minimum thermal conductivities of cermet M3AlN

https://doi.org/10.1016/j.jssc.2014.04.008Get rights and content

Highlights

  • We calculated three anti-perovskite cermets with first-principles theory.

  • We illustrated 3D Young modulus and found the anomalous anisotropy.

  • We explained the anomaly and calculated the minimum thermal conductivities.

Abstract

The electronic structures and elastic anisotropies of cubic Ti3AlN, Zr3AlN, and Hf3AlN are investigated by pseudopotential plane-wave method based on density functional theory. At the Fermi level, the electronic structures of these compounds are successive with no energy gap between conduct and valence bands, and exhibit metallicity in ground states. In valence band of each partial density of states, the different orbital electrons indicate interaction of corresponding atoms. In addition, the anisotropy of Hf3AlN is found to be significantly different from that of Ti3AlN and Zr3AlN, which involve the differences in the bonding strength. It is notable that Hf3AlN is a desired thermal barrier material with the lowest thermal conductivity at high temperature among the three compounds.

Graphical abstract

  • 1.

    Young׳s moduli of anti-perovskite Ti3AlN, Zr3AlN, and Hf3AlN in full space.

  • 2.

    Electron density differences on crystal planes (1 0 0), (2 0 0), and (1 1 0) of anti-perovskite Zr3AlN.

  1. Download : Download full-size image

Introduction

Reports on the outstanding hardness and abrasive properties of transition metal ternary systems have generated scientists׳ interests [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16]. Among them, a kind of cermet, named MAX, is successfully developed incorporating both metals and ceramics properties, such as high hardness, high elastic modulus, corrosion resistance, oxidation resistance, damage tolerance, excellent machinability, and electrical conductivity. In the chemical formula “MAX”, M represent a few groups of early transition metals, A stand for IIIA or IVA group elements, and X is C or N atom. Among them, nearly a hundred kinds of monophase ternary nitrides and carbides have been reported by Nowotny et al. [2] as early as 1960s, which are known as M2AX, M3AX2, and M4AX3 phases. And the subsequent studies proved the existence of advanced MAX phases, such as M5AX4 M6AX5 M7AX6 [3], [4], [5].

Recently a new ternary cermet Ti3AlN was found at the temperature of 1273 K [17]. Other than Mn+1AlNn of hexagonal structures, Ti3AlN has cubic structure with two prominent advantages, i.e. not easy to slip and more closely packed when attached to material surfaces. That means they possess stronger adhesive force and do not easily fall off. Kanchana [18] has investigated the mechanical properties of this material by first principle calculation, and pointed out that Ti3AlN is more ductile than Ti3Al. The results are attributed to the less covalent Ti–N hybridization. It is known that Ti, Zr, and Hf belong to the same group in the elements table. As the physical properties of cubic TiN, ZrN, and HfN have been discussed widely [19], it is easy to associate that Ti3AlN, Zr3AlN and Hf3AlN may manifest some similar properties. Unfortunately, their elastic or thermal properties are not completely clear. Therefore, the applications of Ti3AlN, furthermore Zr3AlN and Hf3AlN (of course the latter two are not founded experimentally yet), are far from implementation. Hence it is necessary to study them together, collect facts, conclude some rules, and predict the possible properties theoretically. The preliminary research is very important for the potential applications. By contrast with cubic TiN, ZrN, and HfN, an in-depth research on cubic Ti3AlN, Zr3AlN, and Hf3AlN aims for emerging that Al atoms affect the physical properties of Ti–N, Zr–N, and Hf–N systems, thereby providing ideas for modifying experiments on the relevant materials.

Section snippets

Calculations

The lattice structure of cermet M3AlN is anti-perovskite belonging to Pm-3m, space group where the N atom occupies the position 1b, the Al atom occupies the position 1a, and the M atom occupies the position 3c (Fig. 1).

The first principles calculation was performed with the CASTEP code [20] based on DFT [21]. The electronic exchange-correlation terms were described by Ceperley–Alder–Perdew–Zunger method under local density approximation (LDA) [22] and Perdew–Burke–Ernzerhof method under

Electronic structures

Fig. 2 shows the energy band structures of Ti3AlN, Zr3AlN, and Hf3AlN, where the red dotted lines represent the Fermi level. In these band structures with no energy gaps, the energy bands pass Fermi levels from conduct bands to valence bands, which indicate the existence of free electrons. By analyzing densities of states (Fig. 3), it is primarily attributed to Ti 3d, Zr 4d, and Hf 5d states electrons, respectively. Moreover, the energy bands near the Fermi level determine the electric

Conclusion

Electronic structures, elastic properties, and the minimum thermal conductivities of Ti3AlN, Zr3AlN, and Hf3AlN were calculated based on DFT. The electronic structures show that there are no band gaps between conduct bands and valence bands, and exhibit metallicity in ground states. Hence, the density of states of all orbital electrons between transition metal and Al atoms as well as between transition metal and N atoms overlapped in the valence band, which corresponds to the difference

Acknowledgments

The authors are grateful to the National Natural Science Foundation of China (Grants nos. 11102169, 51101130, and 51171156).

References (41)

  • M.W. Barsoum

    Prog. Solid State Chem.

    (2000)
  • M.S. Islam et al.

    Physica B

    (2011)
  • J.C. Schuster et al.

    J. Solid State Chem.

    (1984)
  • Z.Q. Chen et al.

    J. Alloys Compd.

    (2013)
  • D.R. Clarke

    Surf. Coat. Technol.

    (2003)
  • H. Nowotny

    Solid State Chem

    (1970)
  • J.P. Palmquist et al.

    Phys. Rev. B: Condens. Matter

    (2004)
  • Z.J. Lin et al.

    J. Am. Ceram. Soc.

    (2006)
  • J. Zhang et al.

    J. Master Res.

    (2009)
  • J. Emmerlich et al.

    J. Appl. Phys.

    (2004)
  • H. Wolfsgruber et al.

    Monatsh. Chem.

    (1967)
  • O. Wilhelmssona et al.

    Appl. Phys. Lett.

    (2004)
  • J. Etzkorn et al.

    Inorg. Chem.

    (2007)
  • H. Hogberg et al.

    Adv. Sci. Technol

    (2006)
  • A.T. Procopio et al.

    Metall. Mater. Trans. A

    (2000)
  • C.F. Hu et al.

    J. Am. Ceram. Soc.

    (2008)
  • Y.L. Bai et al.

    Solid State Commun

    (2009)
  • M.W. Barsoum et al.

    Annu. Rev. Mater. Res.

    (2011)
  • C.L. Li et al.

    J. Phys. D: Appl. Phys.

    (2009)
  • V. Kanchana

    Europhys. Lett.

    (2009)
  • Cited by (10)

    View all citing articles on Scopus
    View full text