Journal of Materials Science

, Volume 54, Issue 4, pp 3547–3557 | Cite as

Microscopic investigation of local structural and electronic properties of tungsten tetraboride: a superhard metallic material

  • Christopher L. Turner
  • Zoran Zujovic
  • Dimitrios KoumoulisEmail author
  • R. E. TaylorEmail author
  • Richard B. Kaner


Tungsten borides, such as tungsten tetraboride (WB4) exhibit a wide range of appealing physical properties, including superhardness, chemical inertness and electronic conductivity. Among the various tungsten borides, the most puzzling remains WB4, with its crystal structure to linger in question for over half a century (Lech et al. in Proc Natl Acad Sci USA 112:3223–3228, 2015). In the present investigation, polycrystalline WB4 samples have been synthesized with two different methods and characterized at the atomic level by combining X-ray diffraction, scanning electron microscopy and nuclear magnetic resonance spectroscopy. The 11B multiple quantum MAS experiment revealed a range of boron sites that were not resolved within the experiment. This result is in contrast to the 11B MAS spectrum of WB2 with four resolved, discernible boron resonances. However, despite the structural complexity and boron-site variety in WB4, the detection of a single exponential of 11B spin–lattice relaxation recovery suggested that all of the boron sites relaxed with a single time constant. The Knight shift (K) was found to be independent of temperature while the \( T_{1}^{ - 1} \) was governed by the Korringa law with a Korringa product T1T = 350 sK across the entire temperature range (168–437 K) of this study. The measured Korringa product was small, indicating substantial spin–lattice relaxation resulting from coupling with the conduction carriers. The abovementioned experimental results not only clearly rule out structures, such as the “MoB4-type phase” of WB4, with the resulting Fermi level in the pseudo-gap as has previously been predicted theoretically; but they also provide a comprehensible and valuable insight into the structural and electronic properties of WB4 at the atomic level.



This research is supported by the National Science Foundation MRI program Grant No. 1532232 (R.E.T., R.B.K.) and DMR-1506860 (R.B.K.).

Compliance with ethical standards

Conflict of interest

C.L.T. works with SuperMetalix, Inc., a company who is developing products based on superhard metals using patents licensed from UCLA. R.B.K. also has a financial interest in SuperMetalix, Inc. The authors Z.Z, D.K. and R.E.T. declare no conflict of interest.


  1. 1.
    Kayhan M, Hildebrandt E, Frotscher M, Senyshyn A, Hofmann K, Alff L, Albert B (2012) Neutron diffraction and observation of superconductivity for tungsten borides, WB and W2B4. Solid State Sci 14:1656–1659CrossRefGoogle Scholar
  2. 2.
    Cheng X-Y, Chen X-Q, Li D-Z, Li Y-Y (2014) Computational materials discovery: the case of the W–B system. Acta Cryst C 70(2014):85–103CrossRefGoogle Scholar
  3. 3.
    Cheng X, Zhang W, Chen X-Q, Niu H, Liu P, Du K, Liu G, Li D, Cheng H-M, Ye H, Li Y (2013) Interstitial-boron solution strengthened WB3+x. Appl Phys Lett 103:171903CrossRefGoogle Scholar
  4. 4.
    Lech AT, Turner CL, Mohammadi R, Tolbert SH, Kaner RB (2015) Structure of superhard tungsten tetraboride: a missing link between MB2 and MB12 higher borides. Proc Natl Acad Sci USA 112:3223–3228CrossRefGoogle Scholar
  5. 5.
    Mohammadi R, Lech AT, Xie M, Weaver BE, Yeung MT, Tolbert SH, Kaner RB (2011) Tungsten tetraboride, an inexpensive superhard material. Proc Natl Acad Sci USA 108:10958–10962CrossRefGoogle Scholar
  6. 6.
    Itoh H, Matsudaira T, Naka S (1987) Formation process of tungsten borides by solid state reaction between tungsten and amorphous boron. J Mater Sci 22:2811–2815. CrossRefGoogle Scholar
  7. 7.
    Koval’chenko MS, Bodrova LG, Nemchencko VF, Kolotun VF (1979) Some physical properties of the higher borides of molybdenum and tungsten. J Less-Common Met 67:357–362CrossRefGoogle Scholar
  8. 8.
    Burdett JK, Canadell E, Miller GJ (1986) Electronic structure of transition-metal borides with the AlB2 structure. J Am Chem Soc 108:6561–6568CrossRefGoogle Scholar
  9. 9.
    Turner CL, Koumoulis D, Li G, Zujovic Z, Taylor RE, Kaner RB (2018) Synthesis and characterization of aluminum diboride products using 27Al, 11B NMR and ab initio studies. J Mater Sci 53:3309–3322. CrossRefGoogle Scholar
  10. 10.
    Żogał OJ, Fojud Z, Herzig P, Pietraszko A, Lyashchenko AB, Jurga S, Paderno VN (2009) Crystal structure, electric field gradient, and electronic charge densities in ReB2: a single crystal X-ray, 11B nuclear magnetic resonance, and first-principles study. J Appl Phys 106:033514CrossRefGoogle Scholar
  11. 11.
    Turner CL, Zujovic Z, Koumoulis D, Taylor RE, Kaner RB (2017) 11B NMR study of WB2. J Phys Chem C 121:1315–1320CrossRefGoogle Scholar
  12. 12.
    Kiessling R (1947) The crystal structures of molybdenum and tungsten borides. Acta Chem Scand 1:893–916CrossRefGoogle Scholar
  13. 13.
    Chretien A, Helgorsky J (1961) On new boride compositions of molybdenum and tungsten, MoB4 and WB4. CR (East Lansing, Mich) 252(5):742–744Google Scholar
  14. 14.
    Bodrova LG, Koval’chenko MS, Serebryakova TI (1974) Preparation of tungsten tetraboride. Poroshkovaya Metallurgiya 133:1–4Google Scholar
  15. 15.
    Jaeger C, Hemmann F (2014) EASY: a simple tool for simultaneously removing background, deadtime and acoustic ringing in quantitative NMR spectroscopy—part I: basic principle and applications. Solid State NMR 57–58:22–28CrossRefGoogle Scholar
  16. 16.
    Fenzke D, Freude D, Frohlich T, Haase J (1984) NMR intensity measurements of half-integer quadrupole nuclei. Chem Phys Lett 111:171–175CrossRefGoogle Scholar
  17. 17.
    Mann P, Klinowski J, Trokiner A, Zanni H, Papon P (1988) Selective and non-selective NMR excitation of quadrupolar nuclei in the solid state. Chem Phys Lett 151:143–160CrossRefGoogle Scholar
  18. 18.
    Yesinowski JP (2015) Finding the true spin–lattice relaxationtime for half-integral nuclei with nonzero quadrupole couplings. J Magn Reson 252:135–144CrossRefGoogle Scholar
  19. 19.
    Frydman L, Harwood JS (1995) Isotropic spectra of half-integer quadrupolar spins from bidimensional magic-angle spinning NMR. J Am Chem Soc 117:5367–5368CrossRefGoogle Scholar
  20. 20.
    Medik A, Harwood JS, Frydman L (1995) Multiple-quantum magic-angle spinning NMR: a new method for the study of quadrupolar nuclei in solids. J Am Chem Soc 117:12779–12787CrossRefGoogle Scholar
  21. 21.
    Harris RK, Becker ED, de Menezes SMC, Goodfellow R, Granger P (2001) NMR nomenclature, nuclear spin properties, and conventions for chemical shifts (IUPAC recommendations 2001). Pure Appl Chem 73:1795–1818CrossRefGoogle Scholar
  22. 22.
    Bishop M, Shahid N, Yang J, Barron AR (2004) Determination of the mode and efficacy of the cross-linking of guar by borate using MAS 11B NMR of borate cross-linked guar in combination with solution 11B NMR of model systems. Dalton Trans 17:2621–2624CrossRefGoogle Scholar
  23. 23.
    Massiot D, Farnan I, Gautier N, Trumeau D, Trokiner A, Coutures JP (1995) 71Ga and 69Ga nuclear magnetic resonance study of β-Ga2O3: resolution of four- and six-fold coordinated ga sites in static conditions. Solid State NMR 4:241–248CrossRefGoogle Scholar
  24. 24.
    Andrew ER, Tunstall DP (1961) Spin–lattice relaxation in imperfect cubic crystals and in noncubic crystals. Proc Phys Soc Lond 78:1–11CrossRefGoogle Scholar
  25. 25.
    Korringa J (1950) Nuclear magnetic relaxation and resonance line shift in metals. Physica 16:601–610CrossRefGoogle Scholar
  26. 26.
    Nisson DM, Dioguardi AP, Klavins P, Lin CH, Shirer K, Shockley AC, Crocker J, Curro NJ (2013) Nuclear magnetic resonance as a probe of electronic states of Bi2Se3. Phys Rev B 87:195202CrossRefGoogle Scholar
  27. 27.
    Turner CL, Taylor RE, Kaner RB (2015) 10B and 11B NMR study of elemental boron. J Phys Chem C 119:13807–13813CrossRefGoogle Scholar
  28. 28.
    Paluch S, Żogal OJ, Peshev P (2004) Low electron density of states at the boron site of TMB2 (TM = Ti, Zr, Haf, and Nb): a 11B NMR study. J Alloys Compd 383:176–179CrossRefGoogle Scholar
  29. 29.
    Lue CS, Lai WJ (2005) NMR study of B-2p fermi-level density of states in the transition metal diborides. Phys Stat Sol (B) 242:1108–1112CrossRefGoogle Scholar
  30. 30.
    Vajeeston P, Raviindran P, Ravi C, Asokamani R (2001) Electronic structure, bonding, and ground-state properties of AlB2-type transition-metal diborides. Phys Rev B 63:045115CrossRefGoogle Scholar
  31. 31.
    Zhao E, Meng J, Ma Y, Wu Z (2010) Phase stability and mechanical properties of tungsten borides from first principles calculations. Phys Chem Chem Phys 12:13158–13165CrossRefGoogle Scholar
  32. 32.
    Gou H, Li Z, Wang L-M, Lian J, Wang Y (2012) Peculiar structure and tensile strength of WB4: nonstoichiometric origin. AIP Adv 2:012171CrossRefGoogle Scholar
  33. 33.
    Cheng X, Zhang W, Chen X-Q, Niu H, Liu P, Du K, Liu G, Li D, Cheng H-M, Ye H, Li Y (2013) Interstitial-boron solution strengthened WB3+x. Appl Phys Lett 103:171903CrossRefGoogle Scholar
  34. 34.
    Hao X, Xu Y, Wu Z, Zhou D, Liu X, Cao X, Meng J (2006) Low-compressibility and hard materials ReB2 and WB2: prediction from first-principles study. Phys Rev B 74:224112CrossRefGoogle Scholar
  35. 35.
    Baek SH, Suh BJ, Pavarini E, Borsa F, Barnes RG, Bud’ko SL, Canfield PC (2002) NMR spectroscopy of the normal and superconducting states of MgB2 and comparison to AlB2. Phys Rev B 66:104510CrossRefGoogle Scholar
  36. 36.
    Kitaoka Y, Yasuoka H (1980) NMR investigations on the spin fluctuations in itinerant antiferromagnets III. CrB2. J Phys Soc Jpn 49:493–498CrossRefGoogle Scholar
  37. 37.
    Creel RB (1969) Nuclear magnetic resonance in transition metal borides, retrospective theses and dissertation. paper 4097, Iowa State University, Ames, IowaGoogle Scholar

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Authors and Affiliations

  1. 1.Department of Chemistry and BiochemistryUniversity of California, Los AngelesLos AngelesUSA
  2. 2.NMR Centre and the Biocide Toolbox Research Programme, School of Chemical SciencesUniversity of AucklandAucklandNew Zealand
  3. 3.School of Physical Science and TechnologyShanghaiTech UniversityPudong, ShanghaiChina
  4. 4.Department of Materials Science and Engineering and California NanoSystems InstituteUniversity of California, Los AngelesLos AngelesUSA
  5. 5.Department of PhysicsUniversity at Buffalo, SUNYBuffaloUSA

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