Two-dimensional metal NaCu_6.3Sb₃and solid-state transformations of sodium copper antimonides

Abstract

A novel layered compound, NaCuSb, has been successfully synthesized from elements. This unique structure crystallizes in the hexagonal space group P6/mmc and has lattice constants of a = 4.2166(2) Å and c = 24.041(1) Å. The structure consists of complex Cu/Sb 2D blocks separated by Na ions. These blocks contain graphene-like hexagonal layers of either Cu or CuSb. The solid-state transformations in the Na-Cu-Sb system between CuSb-NaCuSb-NaCuSb were explored using annealing at different partial vapor pressures of Na, differential scanning calorimetry, and in situ synchrotron powder X-ray diffraction. Full reversibility of the transformation was observed, indicating that the bulk 3D CuSb phase is capable of reversible intercalation of Na ions, forming layered intercalated phases similar to intercalated graphite. The characterization of the transport properties shows that the metallic nature of the electrical conductivity is preserved, even for the Na-rich phase of NaCuSb. Electronic structure calculations support metallic properties in the Cu-Sb layers and predict that no bands cross the Fermi level across the layers, supporting NaCuSb as a two-dimensional metal.

Synthesis, Crystal and Electronic Structure of Layered AMSb Compounds (A = Rb, Cs; M = Zn, Cd)

“…To date, the ZrBeSi structure type has been well represented in the literature with numerous examples, such as: LiBC, AeMPn ( Ae = Ca, Sr, Ba, Eu; M = Cu, Ag, Au; Pn = P, As, Sb), Ae LiP ( Ae = Sr, Ba), KZn Pn ( Pn = P, As, Sb), K M Te ( M = Cu, Au), and KHg Pn ( Pn = As, Sb) to name a few . Additionally, the flat hexagonal layer can be found in more complex structures, such as the layered NaCu 6.3 Sb 3 compound . Furthermore, there are also examples of structures that deviate slightly from this structure type by a puckering of the hexagonal layer, like in the case of LiZnSb .…”

“…[23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] Additionally, the flat hexagonal layer can be found in more complex structures, such as the layered NaCu 6.3 Sb 3 compound. [39] Furthermore, there are also examples of structures that deviate slightly from this structure type by a puckering of the hexagonal layer, like in the case of LiZnSb. [40] This structure type has gained notoriety since the discovery of the superconductivity in MgB 2 .…”

Thermal Stability and Thermoelectric Properties of NaZnSb

“…Additional peaks in the PXRD pattern (Figure 5) correspond to elemental antimony and a new Na 1−x ZnSb ternary phase, whose structure and properties are currently being investigated. The difference between HT synchrotron powder XRD data and DSC measurement can be a result of the side reaction between Na leached from NaZnSb and silica upon heating [24]. The ratio between the surface area of the silica DSC ampoule and sample is greater in the DSC experiment, promoting the side reaction of Na with SiO 2 .…”

From NaZn4Sb3 to HT-Na1–xZn4–ySb3: Panoramic Hydride Synthesis, Structural Diversity, and Thermoelectric Properties

“…In addition to the compositional space, the synthesis temperature is a decisive factor in the stabilization of a particular compound. In recent years, the advances in in-situ X-ray and neutron diffraction and in-situ TEM methods for reaction monitoring, allow a better understanding of the mechanisms in solid-state reactions [3,[8][9][10][11][12][13][14][15][16][17]. For instance, high-temperature X-ray diffraction data of the Cs/Sn/P/Se systems gave a "panoramic" view of the compositional phase space and allowed for the discovery of multiple new phases [3].…”