Elastic properties, fracture toughness, ideal tensile strength and thermal conductivities of the stable hexagonal WB2, W2B5, WB3 and WB4

Synthesis, crystal structure, and properties of stoichiometric hard tungsten tetraboride, WB4

“…54 Crystal structures of these WB 5 , WB 4.18 and WB 4.86 phases were found to be very similar to those reported earlier for the seemingly "WB 4 " phase and its derivatives. 38,39,42 This nding may suggest that: (i) the stoichiometric WB 5 phase is actually the "parent" for the family of boron-decient phases WB 5Àx (0 # x < 1.6) reported to date; (ii) a genuine stoichiometric WB 4 phase for which a different crystal structure was predicted 31,36,37,48 probably has not been synthesized yet, and previous claims of its synthesis were likely due to confusion with one of the WB 5Àx phases. 54 In this work, we report the rst synthesis of single crystals of the so far "elusive" stoichiometric WB 4 phase and an accurate determination of its crystal structure by single-crystal X-ray diffraction.…”

“…34,54 (f) theoretically predicted stoichiometric WB 4 . 31,36,37,48 The blue spheres represent tungsten atoms, the black spheres are boron atoms, and the partially filled spheres indicate defect B or W sites.…”

“…P6 3 /mmc, a $2.93-2.96 Å, c $10.9-11.0 Å, Fig. 1f), 31,36,37,48 but it has not been experimentally observed to date.…”

“…This fact motivates investigations of other potentially hard tungsten compounds, primarily, borides. [29][30][31][32][33][34][35][36][37] Among them, a phase referred to as "WB 4 ", [38][39][40][41][42][43][44][45][46][47][48][49] and its several derivatives (e.g., W 1Àx B 3 , WB 4Àx , WB 4+x , WB 4.2 , and WB 5Àx ) [50][51][52][53][54][55][56] were identied as highly promising candidates, whose mechanical characteristics (e.g. theoretical and experimental values of H V vary from 30 to 45 GPa (ref.…”

“…We nd that a crystal structure of the genuine WB 4 phase indeed differs from previous experimentally-determined models for the seemingly "WB 4 " phase, 26,38,39,42,44,45,47,49,59 while, it is well consistent with the one predicted for WB 4 . 31,36,37,48 Examinations of mechanical properties of the single-and polycrystalline samples of WB 4 conrm the hard nature of this phase.…”