Rietveld analysis of X-ray diffraction pattern from β-Ta2O5 oxide

Алешина, Л. А.; Loginova, S. V.

doi:10.1134/1.1481927

Cited by 103 publications

(85 citation statements)

References 4 publications

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“…1, where each RDF is the average of at least 10 RDFs from separate diffraction patterns collected from different locations in each coating. It should be noted that the first major peak in the RDF at around 2Å corresponds well to Ta-O and Ti-O distances in many tantalum or titanium oxides [19][20][21]. The second major peak was shown in previous work [13] The correlation between the dependence of mechanical loss and metal-oxygen distances (first peak position) on titanium content is also illustrated in Fig.…”

Section: Correlations Between Structural Parameters and Mechanical Lomentioning

confidence: 69%

Correlations between the mechanical loss and atomic structure of amorphous TiO2-doped Ta2O5 coatings

Bassiri¹,

Evans²,

Borisenko³

et al. 2013

Acta Materialia

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can drop by as much as 40 % when it is doped with TiO 2 . We use a combination of electron diffraction data and atomic modeling using molecular dynamics to probe the atomic structure of these coatings, and examine the correlations between changes in the atomic structure and changes in the mechanical loss of these coatings. Our results show the first correlation between changes in the mechanical loss and experimentally measured changes in the atomic structure resulting from variations in the level of TiO 2 doping in TiO 2 doped Ta 2 O 5 coatings, in that increased homogeneity at the nearest neighbour level appears to correlate with reduced mechanical loss. It is demonstrated that subtle but measurable changes in the nearest neighbour homogeneity in an amorphous material

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Section: Correlations Between Structural Parameters and Mechanical Lomentioning

confidence: 69%

Correlations between the mechanical loss and atomic structure of amorphous TiO2-doped Ta2O5 coatings

Bassiri¹,

Evans²,

Borisenko³

et al. 2013

Acta Materialia

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“…In these studies, the low-temperature Ta 2 O 5 phase was typically modeled by high-symmetry structural models, such as the orthorhombic β model [24], or the hexagonal δ model [15] (See Fig. 1).…”

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confidence: 99%

Hidden Structural Order in OrthorhombicTa2O5

Lee

Kim

et al. 2013

Phys. Rev. Lett.

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We investigate using first-principles calculations the atomic structure of the orthorhombic phase of Ta2O5. Although this structure has been studied for decades, the correct structural model is controversial owing to the complication of structural disorder. We identify a new low-energy highsymmetry structural model where all Ta and O atoms have correct formal oxidation states of +5 and −2, respectively, and the experimentally reported triangular lattice symmetry of the Ta sublattice appears dynamically at finite temperatures. To understand the complex atomic structure of the Ta2O3 plane, a triangular graph-paper representation is devised and used alongside oxidation state analysis to reveal infinite variations of the low-energy structural model. The structural disorder of Ta2O5 observed in experiments is attributed to the intrinsic structural variations, and oxygen vacancies that drive collective relaxation of the O sublattice.Tantalum pentoxide (Ta 2 O 5 ) is one of the most extensively studied transition metal oxides due to its potential for technological applications such as anti-reflection coatings, photocatalysis, and high-k dielectrics for highdensity transistors [1][2][3]. It has recently attracted interest as the material of choice for resistance-change memory and the related memristor [4][5][6], however, its crystalline structure, which is critical to its unique structural and electronic properties, is still unclear.Ta 2 O 5 has an orthorhombic phase up to ∼ 1350 • C, above which a transition to a tetragonal phase occurs [7,8]. Although the low-temperature orthorhombic phase is of technological relevance, it has proven difficult to characterize structurally. Early X-ray diffraction studies [9,10] found that the orthorhombic Ta 2 O 5 phase consists of two-dimensional (2D) layers of Ta 2 O 3 in the ab plane, and two-fold coordinated O atoms that connect the Ta atoms in adjacent layers (forming linear chains of -Ta-O-Ta-O-Ta-) along the c direction. In the Ta 2 O 3 plane, it was understood that the Ta atoms form a triangular arrangement, but the arrangement of O atoms was unresolved, with many weak superstructure lines [10]. Later, Roth and coworkers reported that the Ta 2 O 3 plane consists of a disordered array of Ta atoms in octahedral and pentagonal bipyramidal arrangements, with an 11-fold increase of the lattice parameters in the b direction [11]. The superstructure periodicity was shown to change when aliovalent cations, such as W or Li, were incorporated in small amounts to stabilize the phase [12,13]. The superstructures consist of a set of small-unit basic structures and invoked the concept of infinitely adaptive structures [14] for nonstoichiometric Ta 2 O 5−x thatwithin certain composition limits-every composition orders into a different superstructure.Extensive theoretical studies have been made with regards to the bulk properties, dielectric response, and oxygen vacancies (and their diffusion) of Ta 2 O 5 [15][16][17][18][19][20][21][22][23]. In these studies, the low-temperature Ta 2 O 5 pha...

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“…There is also no similarity to the structure of, e.g., any known oxide or hydride. Ta 2 O 5 has two low-temperature phases, b and d. The b-phase has an orthorhombic structure with a = 0.6217 nm, b = 0.3677 nm, and c = 0.7794 nm [49]. The d-phase has a hexagonal structure with a = 0.7191 nm and c = 0.3831 nm [50].…”

Section: Discussionmentioning

confidence: 97%

Observations of fcc and hcp tantalum

et al. 2015

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The metal tantalum has many varied uses including in microelectronics (especially in capacitors) as thin films, in medical applications as an implant material or for surgical instruments, in X-ray lithography for masks, and in high-temperature structural applications. Ta is particularly useful because it is relatively ductile, refractory in nature, and does not readily react with corrosive materials. The body-centered cubic (bcc) crystal structure of pure Ta, also known as the a-phase, is the most commonly observed, but Ta is also known to exist in two other allotropes, one tetragonal and the other (much less-wellknown) face-centered cubic (fcc). The tetragonal form (bTa) has been produced by various deposition techniques and often occurs mixed with the a-phase; the fcc phase has only previously been reported in thin films deposited by thermal evaporation. There have been other reports of 'bcc metals' such as V and Fe existing with an fcc crystal structure when the metal is deposited as a thin film. In the present study, fcc Ta with a = 0.43 nm has been observed using transmission electron microscopy in bulk samples of Ta that have been subjected to quasi-static tensile deformation that was so large as to cause fracture of the material. The fcc phase has a relatively small grain size but appears to be stable at room temperature. It is also shown that relatively large grains (10-20 nm in diameter) of Ta can also exist with an hcp structure with a = 0.304 nm and c = 0.494 nm.

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Rietveld analysis of X-ray diffraction pattern from β-Ta2O5 oxide

Cited by 103 publications

References 4 publications

Correlations between the mechanical loss and atomic structure of amorphous TiO2-doped Ta2O5 coatings

Correlations between the mechanical loss and atomic structure of amorphous TiO2-doped Ta2O5 coatings

Hidden Structural Order in OrthorhombicTa2O5

Observations of fcc and hcp tantalum

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