Local Ordering in the Intermetallic Compound Cu_1-xAl₂ Studied by NMR Spectroscopy

Abstract

The relation between the homogeneity range and the chemical bonding in the intermetallic compound Cu 1-x Al 2 was investigated by nuclear magnetic resonance spectroscopy. 63,65 Cu and 27 Al NMR spectroscopy experiments were carried out on Al-and Cu-rich powder samples of the binary phase Cu 1-x Al 2 . Solely combined application of several NMR techniques like orientational dependent measurements of powder samples aligned in a magnetic field and spin echo double resonance (SEDOR) experiments revealed the formation of vacancies at the copper sites. Two other possible mechanisms substitution of Cu by Al and vice versa, were excluded.

Organometallic Access to Intermetallic θ‐CuE2 (E = Al, Ga) and Cu1–xAlx Phases

“…In all Cu/Al samples described in this work, the residual content is C, H, and O, which stems from oxidation and hydrocarbon artifacts (solvent and/or decomposition products) that are not fully desorbed from the particle surface. The 27 Al MAS NMR of the sample (diluted with SiO 2 powder) reveals a strong signal at δ = 1492 ppm (Figure 5a), which is assignable to the Al Knight shift in θ-CuAl 2 in the range of 1480 [38] to 1500 [7] and 1530 ppm [39] and thus in agreement with the literature. A strong signal of Al 2 O 3 [37] at δ = 31.3 ppm is visible, which is indicative of partial oxidation of the sample (see Supporting Information).…”

“…In the 27 Al MAS NMR spectrum of the powder, the Knight shift of Al at δ = 1494 ppm is observed, which is in good agreement with the previously published data for θ-CuAl 2 . [7,38,39] The TEM image of the sample, which was www.eurjic.orgsuspended in toluene upon sonication, exhibits strongly agglomerated particles (Figure 5b) . The EDX analysis of several selected particle regions confirmed the expected molar Cu/Al ratio of 1:2 (Ϯ10 %).…”

“…[5] Recently, Grin et al presented a full structural characterization of the θ-CuAl 2 phase by single-crystal X-ray structural analysis ( Figure 1) and detailed solid-state 63,65 Cu NMR spectroscopy. [6,7] El-Boragy et al synthesized the hexagonal Cu 0.58 Al 0. 42 phase as well as the monoclinic Cu 0.51 Al 0.49 phase by heat treatment.…”

Electronic Structure, Chemical Bonding, and Solid‐State NMR Spectroscopy of the Digallides of Ca, Sr, and Ba

“…A similar orientation of the crystallites in a magnetic field was also observed in Cu 1Àx Al 2 with x = 0.025 in which the axis of alignment was parallel to the interpenetrating honeycomb-like 6 3 nets of the Al atoms. [33] The origin of the reorientation of the crystallites in the magnetic field might result from a characteristic feature of the bonding situation being similar in both types of compounds. This is most probably the honeycomb-like covalently bonded nets of a distinct type of atom.…”

Preparation of titanium diboride TiB2 by spark plasma sintering at slow heating rate

“…A significant alignment of the [0 0 0 1] axes of the fiber-like crystallites along the pressure direction can be recognized from the COM of Section 3. The forced orientation of the crystallites is probably caused by the interaction of the magnetic field of the dc current during the SPS treatment with the crystal lattice of the TiB 2 [16,17].…”