Diagram of state of the chromium-boron system

Portnoi, K. I.; Romashov, V. M.; Romanovich, I. V.

doi:10.1007/bf00776077

Cited by 20 publications

(9 citation statements)

References 7 publications

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“…The brand-new oP10 structure has indeed been confirmed for CrB 4 by recent experiments 6,27 (see the Fe-B section for more related information). The tI32-Cr 5 B 3 phase reported in literature [148][149][150] is stable in our database. However, CrB 2 has been reported to adopt the hP3 (SG#191) configuration (the AlB 2 prototype with flat boron layers) 150,151 , while our calculations indicate that the structure is unstable by 70 meV/atom with respect to hP12 (SG#194) (the WB 2 prototype with a mixture of flat and buckled boron layers).…”

Section: Cr-bmentioning

confidence: 53%

Stability of 41 metal–boron systems at 0GPa and 30GPa from first principles

Geest

Kolmogorov

2014

Calphad

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A multitude of observed boron-based materials have outstanding superconducting, mechanical, and refractory properties. Yet, the structure, the composition, and the very existence of some reported metal boride (M-B) compounds have been a subject of extensive debate. This density functional theory work seeks to set a baseline for current understanding of known metal boride phases as well as to identify new synthesizable candidates. We have generated a database of over 12,000 binary M-B entries for pressures of 0 and 30 GPa producing the largest scan of compositions and systems in this materials class. The 175 selected crystal structures include both observed prototypes and new ones found with our evolutionary ground state search. The metals considered are: Al, and Zr. Based on the formation energy calculated at zero pressure and temperature 4 new M-B phases or structures have been predicted, while a number of previously reported compounds have been shown to be unstable. At 30 GPa, changes in the convex hulls are expected to occur in 18 out of 41 M-B systems, which is used to indicate regions of the periodic table (for metal borides) that require further investigation from the community. Analysis of the collected information has revealed a nearly linear relationship between the magnetic moment per atom and the metal content for all the Fe-B, Co-B, and Ni-B structures within 0.15 eV/atom of the stability tie line. Both GGA-PBE and LDA-PW functionals were used to provide an understanding of the systematic error introduced by the choice of the exchange-correlation functional.arXiv:1310.4157v2 [cond-mat.mtrl-sci]

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Section: Cr-bmentioning

confidence: 53%

Stability of 41 metal–boron systems at 0GPa and 30GPa from first principles

Geest

Kolmogorov

2014

Calphad

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“…Tungsten diboride, WB 2 , is present at concentrations of Cr from 0–41.5 at. % Cr, and in addition, CrB 2 ( P 6 /mmm , JCPDS 01–089–3533) forms at concentrations of chromium from 25.0–50.0 at. % Cr.…”

Section: Resultsmentioning

confidence: 99%

Effects of Variable Boron Concentration on the Properties of Superhard Tungsten Tetraboride

et al. 2017

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Tungsten tetraboride is an inexpensive, superhard material easily prepared at ambient pressure. Unfortunately, there are relatively few compounds in existence that crystallize in the same structure as tungsten tetraboride. Furthermore, the lack of data in the tetraboride phase space limits the discovery of any new superhard compounds that also possess high incompressibility and a three-dimensional boron network that withstands shear. Thus, the focus of the work here is to chemically probe the range of thermodynamically stable tetraboride compounds with respect to both the transition metal and the boron content. Tungsten tetraboride alloys with a variable concentration of boron were prepared by arc-melting and investigated for their mechanical properties and thermal stability. The purity and phase composition were confirmed by energy dispersive X-ray spectroscopy and powder X-ray diffraction. For variable boron WB, it was found that samples prepared with a metal to boron ratio of 1:11.6 to 1:9 have similar hardness values (∼40 GPa at 0.49 N loading) as well as having a similar thermal oxidation temperature of ∼455 °C. A nearly single phase compound was successfully stabilized with tantalum and prepared with a nearly stoichiometric amount of boron (4.5) as WTaB. Therefore, the cost of production of WB can be decreased while maintaining its remarkable properties. Insights from this work will help design future compounds stable in the adaptable tungsten tetraboride structure.

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“…In addition to the compounds crystallizing with the Gd 5 Si 4type, in each reaction there were also crystals of RE 5À x Ca x Ge 3 (both with the hexagonal Mn 5 Si 3 type and/or the tetragonal Cr 5 B 3 type). [18,19] Through optimization of the reaction conditions, nearly phase-pure samples of the hexagonal RE 5À x Ca x Ge 3 phases (with the early rare-earth metals only) could be synthesized and their magnetic response studied; [20] to date the title RE 5À x Ca x Ge 4 phases, as well as the tetragonal RE 5À x Ca x Ge 3 have not been made as phase-pure samples. Lowering or raising the reaction temperature was explored, but without success-multiphase products were always present.…”

Section: Synthesismentioning

confidence: 99%

Calcium Substitution in Rare‐earth Metal Germanides with the Gd₅Si₄ Type Structure

Suen¹,

Bobev

2022

Zeitschrift anorg allge chemie

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An extended series of rare-earth metal calcium germanides have been synthesized and structurally characterized. The compounds have the general formula RE 5À x Ca x Ge 4 (1.5 < x < 3.6; RE = rare-earth metal; Ce, Nd, Sm, TbÀ Lu) and their structures have been established from single-crystal X-ray diffraction methods. They crystallize with the Gd 5 Si 4 -type in the orthorhombic space group Pnma (No. 62; Z = 4; Pearson symbol oP36), where the germanium atoms are interconnected into two kinds of Ge 2 -dimers, formally [Ge 2 ] 6À . These studies show that Ca can be successfully incorporated into the host RE 5 Ge 4 structure, whereby trivalent rare-earth metal atoms can be substituted by divalent calcium atoms. Rare-earth metal and calcium atoms are arranged in distorted trigonal prisms and cubes, centered by either Ge or Ca atoms. On one of the metal sites, the substitution is preferential and in 9 out of the 10 refined structures, the Wyckoff site 4c is found almost exclusively occupied by Ca. On the other two metal sites the substitution patterns appear to be governed by the mismatch between the size of the RE 3 + and Ca 2 + ions. This work further demonstrates the ability for the Gd 5 Si 4 structure type to accommodate the substitution of a non-magnetic element while maintaining the global structural integrity.

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Diagram of state of the chromium-boron system

Cited by 20 publications

References 7 publications

Stability of 41 metal–boron systems at 0GPa and 30GPa from first principles

Stability of 41 metal–boron systems at 0GPa and 30GPa from first principles

Effects of Variable Boron Concentration on the Properties of Superhard Tungsten Tetraboride

Calcium Substitution in Rare‐earth Metal Germanides with the Gd₅Si₄ Type Structure

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Diagram of state of the chromium-boron system

Cited by 20 publications

References 7 publications

Stability of 41 metal–boron systems at 0GPa and 30GPa from first principles

Stability of 41 metal–boron systems at 0GPa and 30GPa from first principles

Effects of Variable Boron Concentration on the Properties of Superhard Tungsten Tetraboride

Calcium Substitution in Rare‐earth Metal Germanides with the Gd5Si4 Type Structure

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Product

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Calcium Substitution in Rare‐earth Metal Germanides with the Gd₅Si₄ Type Structure