?-TaN, eine Hochdruckform von Tantalnitrid

Bräuer, G.; Mohr, Ernst; Neuhaus, A.; Skokan, A.

doi:10.1007/bf00905439

Cited by 45 publications

(29 citation statements)

References 2 publications

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“…Heating cubic ␦-TaN in vacuum leads to a transformation to -TaN in the WC-structure type [7]. This is consistent with experiments by Brauer et al [8], who found the WC-structure type -TaN at high pressure syntheses in the pressure range of 2-10 GPa at 1073-1233 K. In all these experiments, the analyses of the products were done ex situ on quenched samples, and in all these studies the starting compound was -TaN. It was later shown [3] that ␦-TaN could be produced from -TaN by heating at high temperatures (2273 K) under at least 0.001 GPa (10 bar) N 2 -pressure.…”

Section: Introductionsupporting

confidence: 82%

“…Other synthesis routes for the production of ␦-TaN have also been explored (for a brief review see Mashimo Table 1 Overview of stoichiometric tantalum nitrides. References: (1) Christensen and Lebech [4], (2) Brauer et al [8], (3) Gatterer et al [3], (4) Brauer and Zapp [5,6], (5) Fontbonne and Gilles [13], (6) Conroy and Christensen [14], Terao [2], (7) Zerr et al [12], and (8) Strähle [15], Brese et al [16]. Theoretical values are from the present study.…”

Section: Introductionmentioning

confidence: 79%

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In situ observation of the reaction of tantalum with nitrogen in a laser heated diamond anvil cell

Friedrich

Winkler

Bayarjargal

et al. 2010

Journal of Alloys and Compounds

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Section: Introductionsupporting

confidence: 82%

Section: Introductionmentioning

confidence: 79%

In situ observation of the reaction of tantalum with nitrogen in a laser heated diamond anvil cell

Friedrich

Winkler

Bayarjargal

et al. 2010

Journal of Alloys and Compounds

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“…The nitrogen atoms center the trigonal prisms formed by the tantalum atoms. The unit cell observed for this hexagonal phase (a ϭ 2.936 Å , c ϭ 2.885 Å ) by Brauer et al [8] is rather similar to that obtained by Mashimo and Tashiro [9] (a ϭ 2.938 Å , c ϭ 2.868 Å ). The hexagonal ε-TaN phase transforms into θ-TaN at pressures of 20Ϫ100 kbar and at 800Ϫ960°C, or under mechanical alloying conditions.…”

supporting

confidence: 75%

“…The hexagonal ε-TaN phase transforms into θ-TaN at pressures of 20Ϫ100 kbar and at 800Ϫ960°C, or under mechanical alloying conditions. [8,9] Ta 3 N 5 , the nitrogen-richest phase, has a pseudobrookite (Fe 2 TiO 5 )-type [17] structure. This structure contains octahedrally coordinated tantalum atoms, while the nitrogen atoms are both three-and four-coordinate.…”

mentioning

confidence: 99%

Plasma‐Enhanced CVD Synthesis and Structural Characterization of Ta₂N₃

2004

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Keywords: Tantalum / Nitrides / Plasma-enhanced chemical vapor deposition / X-ray diffraction / Electron microscopy Microcrystalline tantalum nitride films were prepared on various substrates from TaCl 5 precursor and nitrogen gas using the plasma-enhanced chemical vapor deposition (PECVD) method. Syntheses carried out at 600−650°C led to single-phase samples of the tantalum nitride Ta 2 N 3 with a defect fluorite-type structure. The anion vacancies were found to order resulting in a 2 ϫ 2 ϫ 2 cubic superstructure of the C-Ln 2 O 3 type (space group Ia3 , Z = 16) with a = 9.8205(4) Å according to a Rietveld refinement of the X-ray IntroductionThe binary TaϪN system is quite rich in compounds with well-defined and variable stoichiometries. The formal oxidation state of tantalum covers the whole range from nearly zero to the maximum of ϩ5. These compounds can be divided into four groups: solid solutions of nitrogen in tantalum, the phase with the approximate stoichiometry Ta 2 N, three phases with a nearly 1:1 composition, and nitrogenrich nitrides. A few comprehensive reviews of tantalum nitride structural chemistry are available.[1Ϫ3] Results of the previous structural studies in this binary system are summarized in Table 1.Up to 5 at.% of nitrogen can be dissolved in the bodycentered cubic lattice of elemental tantalum, for example by heating of Ta powder in ammonia at 600Ϫ700°C.[3] The lattice constant of such solid solutions increases slightly to 3.315Ϫ3.369 Å compared to that of the pure metal (a ϭ 3.311 Å ). Observation of additional weak reflections suggests a cubic superstructure with the unit cell tripled in all directions and with a β ϭ 3a α ϭ 10.11 Å . The γ-phase with the composition range TaN 0.41Ϫ0.5 , also denoted as β-Ta 2 N, [4] crystallizes with a hexagonal unit cell.[1Ϫ4] Its crystal structure can be described as a hexagonal close packing of the tantalum atoms with the nitrogen atoms filling half of the octahedral interstices. While the earlier studies suggested a statistical distribution, [1,2] electron- [3] and neutron-diffraction [4] investigations revealed a trigonal P31m supercell with aЈ ϭ Ί3a, isostructural to β-Nb 2 N [14] and of the anti-Li 2 ZrF 6 -type.[15] The γ-phase can be obtained by nitriding of tantalum powder in gaseous ammonia at 800Ϫ900°C or from the elements at 2000°C. [1,3] The hexagonal ε-phase was proposed by Schoenberg [1] to have a B35 CoSn-type structure with the composition TaN 1.00 ; the same description was given by Brauer and Zapp.[2] In this structure type the nitrogen atoms are at the center of slightly distorted tantalum octahedra. Later, Christensen and Lebech [5] showed that the nitrogen atoms are displaced from these ideal positions reducing their coordination sphere to a square pyramid. The unit cell determined by Christensen and Lebech [5] (a ϭ 5.196 Å , c ϭ 2.911 Å ) is quite similar to that given by the other authors.[1Ϫ3] The ε-phase can be obtained as a product of nitriding of Ta powder at temperatures at Ͼ 1100°C. [1] Another modification of tantalum ...

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“…For h phase, the calculated lattice parameters 2.915 and 2.868 Å 2012) are also in good agreement with the experimental results. 11,24,37 Their difference is within 0.8% and 0.6% for a and c axes, respectively. For d phase, the mismatch of lattice parameter is within 0.9% compared with experimental values.…”

Section: Resultsmentioning

confidence: 80%

Structure and mechanical properties of tantalum mononitride under high pressure: A first-principles study

Chang

Zhao

Zhou

et al. 2012

Journal of Applied Physics

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The structure and mechanical properties of tantalum mononitride (TaN) are investigated at high pressure from first-principles using the plane wave pseudopotential method within the local density approximation. Three stable phases were considered, i.e., two hexagonal phases (e and h) and a cubic d phase. The obtained equilibrium structure parameters and ground state mechanical properties are in excellent agreement with the experimental and other theoretical results. A full elastic tensor and crystal anisotropy of the ultra-incompressible TaN in three stable phases are determined in the wide pressure range. Results indicated that the elastic properties of TaN in three phases are strongly pressure dependent. And the hexagonal h-TaN is the most ultraincompressible among the consider phases, which suggests that the h phase of TaN is a potential candidate structure to be one of the ultraincompressible and hard materials. By the elastic stability criteria, it is predicted that h-TaN is not stable above 53.9 GPa. In addition, the calculated B/G ratio indicated that the e and d phases possess brittle nature in the range of pressure from 0 to 100 GPa. While h phase is brittleness at low pressure (below 8.2 GPa) and is strongly prone to ductility at high pressure (above 8.2 GPa). The calculated elastic anisotropic factors for three phases of TaN suggest that they are elastically highly anisotropic and strongly dependent on the propagation direction.

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?-TaN, eine Hochdruckform von Tantalnitrid

Cited by 45 publications

References 2 publications

In situ observation of the reaction of tantalum with nitrogen in a laser heated diamond anvil cell

In situ observation of the reaction of tantalum with nitrogen in a laser heated diamond anvil cell

Plasma‐Enhanced CVD Synthesis and Structural Characterization of Ta₂N₃

Structure and mechanical properties of tantalum mononitride under high pressure: A first-principles study

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?-TaN, eine Hochdruckform von Tantalnitrid

Cited by 45 publications

References 2 publications

In situ observation of the reaction of tantalum with nitrogen in a laser heated diamond anvil cell

In situ observation of the reaction of tantalum with nitrogen in a laser heated diamond anvil cell

Plasma‐Enhanced CVD Synthesis and Structural Characterization of Ta2N3

Structure and mechanical properties of tantalum mononitride under high pressure: A first-principles study

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Plasma‐Enhanced CVD Synthesis and Structural Characterization of Ta₂N₃