Synthesis and structural characterization of orthorhombic Cu _3–δ Sb ( δ  ≈ 0.1) and hexagonal Cu ₃ Sb _1–x In _x (x ≈ 0.2) phases

Journal Article · Wed Mar 03 00:00:00 EST 2021 · Zeitschrift fuer Kristallographie. Crystalline Materials

DOI:https://doi.org/10.1515/zkri-2021-0003· OSTI ID:1851170

Sinclair, Jordan ^[1]; Baranets, Sviatoslav  ^[1]; Bobev, Svilen  ^[1]

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1. Department of Chemistry and Biochemistry , University of Delaware , Newark , DE 19716 , USA

Cu₃Sb is a known copper-rich phase in the Cu–Sb binary phase diagram. It is reported to be dimorphic, with a low-temperature form adopting the orthorhombic Cu₃Ti structure type (space groupPmmn, No. 59). The high-temperature form crystallizes in the cubic space group $Fm\stackrel{-}{3}m$$$Fm‾{3}m$$(No. 225), and is isostructural with BiF₃. Neither polymorph has been carefully characterized to date, with both structures being assigned to the respective structure type, but never refined. With this study, we provide structural evidence, based on single-crystal and powder X-ray diffraction data that the low-temperature orthorhombic phase exists with a significant amount of defects on one of the Cu-sites. As a result, its composition is not Cu₃Sb, but rather Cu_3–δSb (δ = 0.13(1)). The cubic form could not be accessed as a part of this study, but another Cu-rich phase, Cu₃Sb_≈0.8In_≈0.2, was also identified. It adopts the hexagonal Ni₃Sn structure type (space groupP6₃/mmc, No. 194) and represents an In-substituted variant of a hitherto unknown structural modification of Cu₃Sb. Whether the latter can exist as a binary phase, or what is the minimum amount of In inclusions needed to stabilize it remains to be determined. Measurements of the thermopower of Cu_3–δSb (δ = 0.13(1)) were conducted in the range of 300–600 K and demonstrated a maximum value of ca. 50 μV/K at 600 K, indicative of ap-type transport mechanism. Electrical resistivity measurements for the same sample confirmed that it exhibits metallic-like behavior, with a room temperature value of 0.43 mΩ cm. Electronic structure calculations show the absence of a band gap. Thermal analysis was utilized to ascertain the congruent melting of both phases.

• Research Organization: Univ. of Delaware, Newark, DE (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: SC0008885
• OSTI ID: 1851170
• Journal Information: Zeitschrift fuer Kristallographie. Crystalline Materials, Vol. 236, Issue 3-4; ISSN 2194-4946
• Publisher: de Gruyter
• Country of Publication: United States
• Language: English

Related Subjects

Crystallography