THE VARIATION OF LATTICE PARAMETER WITH CARBON CONTENT OF TANTALUM CARBIDE<sup>1</sup>

Bowman, A. L.

doi:10.1021/j100905a028

Cited by 143 publications

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“…Using similar crystal growth conditions, Robins determined values of the lattice parameter between 4.4550 and 4.4555 A, the composition of the crystals being determined as TaC0.96. According to the data of Bowman [21], a lattice parameter of 4.456 A corresponds to a composition TaC0.99. Electron microprobe analysis showed that the bulk of each crystal contained only tantalum and carbon but in some crystals one or two small inclusions of iron and carbon were present.…”

Section: Methodsmentioning

confidence: 99%

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Structure and properties of tantalum carbide crystals

Rowcliffe¹,

Warren²

1970

J Mater Sci

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Single crystals of tantalum carbide, up to 2 mm in size have been grown from solution in a bath of molten iron. The slip plane was found to be {1 11} using a two-surface analysis on etch-pitted crystals deformed by microindentation at room temperature. Observations of etch-pit patterns around inclusions suggest that slip occurs on other planes at elevated temperatures. Maximum microhardness values between 3800 and 5200 Knoop (100 gm load) were found at a composition TaC0.83• In regions of crystals with a carbon content less than TaC0.83 a phase transformation was seen close to microhardness indentations in samples decarburised below 2200 ~ C. The mechanical behaviour of tantalum carbide is discussed with reference to a general model for the electronic structure of carbides. IntroductionLike the other monocarbides of the Group IVA and VA transition metals, tantalum carbide possesses the rock salt structure and exists over a wide range of substoichiometry. The most recent phase diagram [1] indicates the composition limits for single-phase tantalum carbide as TaCo.75 to TaC0.9s below about 1500 ~ C. A maximum melting point of 3983 ~ C occurs at TaC0.98. Storms [2] has suggested that the maximum melting point might lie at TaC0.s but he also points out that the actual values of composition and temperature are subject to some uncertainty due to the experimental difficulties in making the measurements [3]. A number of authors have reported a zeta-phase tantalum carbide [4-6] which might be a metastable compound [2,4,5]. Its composition has been determined as TaCo.75 [5] or TaC0.r4 [6], but it also appears to exist over a range of substoichiometry [7]. Yvon and Parth6 [7] have recently shown that the structure of the zeta-phase consists of an arrangement of twelve close-packed metal atoms in a unit cell, with the carbon atoms in octahedral interstices. The arrangement of the metal atoms can be regarded as alternate layers of hcp and fcc stacking, i.e. a close-packed structure containing 50~ stacking faults. Such a structure with a high density of faults is in accord with recent electron microscope studies of *Present address:

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Section: Methodsmentioning

confidence: 99%

“…The calculated lattice parameters were plotted against the Taylor-Sinclair function, 89 + cos20/0), and extrapolated to 0 = 0 ~ The corrected lattice parameter was 4.430 4-0.002 A. This corresponds to a composition TaC0.83+0.01 using the data of Bowman [21].…”

Section: Decarburised Crystalsmentioning

confidence: 99%

Structure and properties of tantalum carbide crystals

Rowcliffe¹,

Warren²

1970

J Mater Sci

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“…This broad range of composition of the carbide phase will reflect itself in a change of certain physical properties of the carbide, as C vacancies will act as powerful scattering centers for electrons and phonons. Within the range, there will be a variation of several properties: the lattice parameters and density, 35 Hall coefficient, 36 transition temperature to the superconducting state, 37 coefficient of thermal expansion, magnetic susceptibility, heat of formation, and ͑technologically important for microelectronics͒ the resistivity. 10 It is clear that one has to take this into account, when searching for reliable contacts for semiconductors.…”

Section: Discussionmentioning

confidence: 99%

Thin film solid-state reactions forming carbides as contact materials for carbon-containing semiconductors

Leroy

Detavernier

Meirhaeghe

et al. 2007

Journal of Applied Physics

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Metal carbides are good candidates to contact carbon-based semiconductors ͑SiC, diamond, and carbon nanotubes͒. Here, we report on an in situ study of carbide formation during the solid-state reaction between thin films. The solid-state reaction was examined between 11 transition metals ͑W, Mo, Fe, Cr, V, Nb, Mn, Ti, Ta, Zr, and Hf͒ and an amorphous carbon layer. Capping layers ͑C or TiN͒ of different thicknesses were applied to prevent oxidation. Carbide formation is evidenced for nine metals and the phases formed have been identified ͑for a temperature ranging from 100 to 1100°C͒. W first forms W 2 C and then WC; Mo forms Mo 2 C; Fe forms Fe 3 C; Cr first forms metastable phases Cr 2 C and Cr 3 C 2−x , and finally forms Cr 3 C 2 ; V forms VC x ; Nb transforms into Nb 2 C followed by NbC; Ti forms TiC; Ta first forms Ta 2 C and then TaC; and Hf transforms into HfC. The activation energy for the formation of the various carbide phases has been obtained by in situ x-ray diffraction.

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“…The matrix y is a NaCl structure with a lattice parameter, at the solubility limit, of 4.4104 A. 10 T h e arrangement of a unit cell of this structure is shown in Figure 2 (not taking into account vacant carbon sites). Any (111) plane of this structure may be considered to consist entirely of carbon or tantalum atoms in a hexagonal arrangement with a spacing of 3.12 A between nearest neighbors.…”

Section: Modelmentioning

confidence: 99%

An Explanation of Microstructures in the Tantalum-Carbon System

Santoro¹,

Probst²

1964

Advances in X-Ray Analysis

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04Compositions in the tantalum-carbon system were prepared by carburizing high-purity tantalum wires. T h e microstructures so produced exhibit regions of a characteristic striated structure identical to those observed by earlier investigators. There are disparities in the literature as to the origin of such structures in the tantalum-carbon system. They have been variously described as "twins," "striated structure," "precipitate," and' "structure of unknown origin." This paper presents conclusive evidence that the structures in question are the result of precipitation on cooling. I n addition, a coherent precipitation model is applied in which it is shown that the lattice relationship { 0 0 0 1 )~~, c~~( 1 1 1 }~~~ can exist with less than 0.5% misfit. This relationship is shown to completely explain the

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THE VARIATION OF LATTICE PARAMETER WITH CARBON CONTENT OF TANTALUM CARBIDE¹

Cited by 143 publications

References 0 publications

Structure and properties of tantalum carbide crystals

Structure and properties of tantalum carbide crystals

Thin film solid-state reactions forming carbides as contact materials for carbon-containing semiconductors

An Explanation of Microstructures in the Tantalum-Carbon System

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THE VARIATION OF LATTICE PARAMETER WITH CARBON CONTENT OF TANTALUM CARBIDE1

Cited by 143 publications

References 0 publications

Structure and properties of tantalum carbide crystals

Structure and properties of tantalum carbide crystals

Thin film solid-state reactions forming carbides as contact materials for carbon-containing semiconductors

An Explanation of Microstructures in the Tantalum-Carbon System

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THE VARIATION OF LATTICE PARAMETER WITH CARBON CONTENT OF TANTALUM CARBIDE¹