Homologous Alkali Metal Copper Rare-Earth Chalcogenides A2Cu2 nLn4Q7+ n(n = 1, 2, 3)

Craig C. Laing, Jiahong Shen, Michael A. Quintero, Benjamin E. Weiss, Yi Xia, Zhi Li, Jiangang He, Chris Wolverton, Mercouri G. Kanatzidis*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

Twenty-seven new members of the A2Cu2nLn4Q7+n (A = Cs, Rb; Ln = La-Nd, Sm, Gd-Yb; Q = S, Se) homologous series were synthesized in one of three structural types (indicated by n = 1, 2, 3). All the compounds contained 3D frameworks with alkali-metal-containing tunnels. For each increment in n, one Cu2Q was added, which was incorporated into the framework as an edge-sharing tetrahedron by replacing a square planar chalcogenide site. High-throughput DFT calculations predicted many of the phases to be thermodynamically stable. These predictions were compared with the synthesis results for the phases formed in each composition space. In the syntheses, heavier lanthanides showed a preference to start forming the n = 3 ACu3Ln2Q5, which is consistent with the predictions. RbCuNd2Se4 and RbCuTb2Se4 were found to be thermally stable under vacuum at temperatures up to 1000 °C. Optical measurements revealed band gaps of 1.55(5) and 1.62(5) eV for CsCuCe2Se4 and RbCuTb2Se4, respectively, and a work function of 4.83(5) eV for CsCuPr2Se4. Additionally, some n = 3 ACu3Ln2Q5 compounds exhibit a negative phonon mode because of a copper atom coordination, which may distort to a trigonal planar geometry at sufficiently low temperatures. The dynamic instabilities and the predicted distortion in the copper tetrahedra for the n = 3 ACu3Ln2Q5 compounds were found to have a linear relationship with the atomic number of the lanthanides and the electronegativity of the lanthanides. The A2Cu2nLn4Q7+n compounds can potentially find application as high-temperature thermoelectric materials and other semiconductors.

Original languageEnglish (US)
Pages (from-to)3409-3422
Number of pages14
JournalChemistry of Materials
Volume34
Issue number7
DOIs
StatePublished - Apr 12 2022

Funding

Synthesis and material characterization were supported by the National Science Foundation through Grant DMR-2003476. J.S. acknowledges the support from the MRSEC program (DMR-1720319) at the Materials Research Center of Northwestern University. This work used the IMSERC Crystallography facility at Northwestern University, which received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-2025633) and Northwestern University. The Ag-microsource diffractometer used in this study was funded by the Major Research Instrumentation Program from the National Science Foundation under the award CHE-1920248. C.C.L. acknowledges Christos D. Malliakas for assistance in setting up the low-temperature single crystal collection. This work used the IMSERC Physical Characterization facility at Northwestern University, which has received support from the SHyNE Resource (NSF ECCS-2025633), and Northwestern University. This work used the EPIC facility of Northwestern University’s NUANCE Center, which received support from the SHyNE Resource (NSF ECCS-2025633), IIN, and Northwestern University’s MRSEC program (NSF DMR-1720139). Computational resources were provided by the National Energy Research Scientific Computing Center (NERSC), U.S. Department of Energy Office of Science User Facility, operated under Contract No. DE-AC02-05CH11231, and the Quest High Performance Computing facility at Northwestern University.

ASJC Scopus subject areas

  • General Chemistry
  • General Chemical Engineering
  • Materials Chemistry

Fingerprint

Dive into the research topics of 'Homologous Alkali Metal Copper Rare-Earth Chalcogenides A2Cu2 nLn4Q7+ n(n = 1, 2, 3)'. Together they form a unique fingerprint.

Cite this