Classification of borides

High‐temperature strength behavior of tantalum diboride to 2000°C

“…The grains that fractured in a transgranular manner indicated that sliding occurred through the grains. According to reports, 1,13,14 the various fracture modes observed in the diborides can be attributed to the orientation of the crystal plane within the grains relative to the plane of the crack propagation, where the dominant slip system {1010} < 1120 > should prevail at elevated temperatures, while the secondary one is {0001} < 11–20 > (which is clearly seen in Figure 1a,b) and is consistent with previous observations for high‐temperature fracture by Demirskyi et al 15 …”

“…Another important factor to consider may be the melting point, as the activation of plasticity can be expected within a different temperature range between 0.5 and 0.7 of the melting temperature 12 . However, NbB 2 and TaB 2 have lower melting points compared to diborides of the IVth group of transition metals 1 …”

“…Tantalum diboride (TaB 2 ) has not been studied as extensively as other transition metal diborides that belong to the ultrahigh‐temperature ceramics family (UHTC), such as ZrB 2 and HfB 2 . Similar to these diborides, TaB 2 has the hexagonal AlB 2 structure 1 and exhibits a relatively high elastic modulus 2,3 …”

Vibrational Properties of Zr(Hf)B2–SiC UHTC Composites by Micro-Raman Spectroscopy

“…2b) and its two Raman active bands could be used to study the vibrational temperature and stress dependent properties of ZrB [80]. The fact was simply overlooked [90][91][92][93] with the unit cell of ZrB containing three atoms [94] . The Zr(Hf) layers alternate with the B layers, however it is not considered as a layered compound contribution to acoustic phonons results from the transition metal sublattice, the high frequency phonons stem from the boron ions, which is expected comparatively weaker electron-phonon interactions.…”

Phase, microstructure evolution and sintering of Sr-doped TiB2 precursors

“…The most popular and wide spread used metal diboride is TiB 2 with the Vickers hardness of 33 GPa, Young's modulus of 545 GPa, thermal conductivity of 64 W/mK and electrical resistivity 20.4 ·cm at 25 • C. [1][2][3] The second group of borides represented by alkaline earth borides of Ca, Sr or Ba crystallize in structures typical of d and f transition metal borides and have similar properties to rare-earth metal borides. [4][5][6] The divalent alkaline-earth hexaborides are investigated due to the properties such as high Curie temperature ferromagnetic semiconductors 7 and also for their thermoelectric properties with very favorable Seebeck coefficients and electrical conductivities, which make them potentially attractive for high-temperature thermoelectric (TE) applications. 8,9 The structures of borides with lower boron content are determined by their metallic lattices, and the structures of higher borides by their boron atoms, which form strong sublattices with pronounced B-B bonds.…”