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Yox P, Cerasoli F, Sarkar A, Kyveryga V, Viswanathan G, Donadio D, Kovnir K. New Trick for an Old Dog: From Prediction to Properties of "Hidden Clathrates" Ba 2Zn 5As 6 and Ba 2Zn 5Sb 6. J Am Chem Soc 2023; 145:4638-4646. [PMID: 36787623 DOI: 10.1021/jacs.2c12435] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
The zinc-antimony phase space has been heavily investigated due to the structural complexity and abundance of high-performing thermoelectric materials. Consequentially, the desire to use zinc and antimony as framework elements to encage rattling cations and achieve phonon-glass-electron-crystal-type properties has remained an enticing goal with only two alkali metal clathrates to date, Cs8Zn18Sb28 and K58Zn122Sb207. Guided by Zintl electron-counting predictions, we explored the Ba-Zn-Pn (Pn = As, Sb) phase space proximal to the expected composition of the type-I clathrate. In situ powder X-ray diffraction studies revealed two "hidden" compounds which can only be synthesized in a narrow temperature range. The ex situ synthesis and crystal growth unveiled that instead of type-I clathrates, compositionally close but structurally different new clathrate-like compounds formed, Ba2Zn5As6 and Ba2Zn5Sb6. These materials crystallize in a unique structure, in the orthorhombic space group Pmna with the Wyckoff sequence i2h6gfe. Single-phase synthesis enabled the exploration of their transport properties. Rattling of the Ba cations in oversized cages manifested low thermal conductivity, which, coupled with the high Seebeck coefficients observed, are prerequisites for a promising thermoelectric material. Potential for further optimization of the thermoelectric performance by aliovalent doping was computationally analyzed.
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Affiliation(s)
- Philip Yox
- Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States.,U.S. Department of Energy, Ames National Laboratory, Ames, Iowa 50011, United States
| | - Frank Cerasoli
- Department of Chemistry, University of California, Davis, Davis, California 95616, United States
| | - Arka Sarkar
- Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States.,U.S. Department of Energy, Ames National Laboratory, Ames, Iowa 50011, United States
| | - Victoria Kyveryga
- Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States
| | - Gayatri Viswanathan
- Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States.,U.S. Department of Energy, Ames National Laboratory, Ames, Iowa 50011, United States
| | - Davide Donadio
- Department of Chemistry, University of California, Davis, Davis, California 95616, United States
| | - Kirill Kovnir
- Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States.,U.S. Department of Energy, Ames National Laboratory, Ames, Iowa 50011, United States
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Ogunbunmi MO, Baranets S, Bobev S. Structural Complexity and Tuned Thermoelectric Properties of a Polymorph of the Zintl Phase Ca 2CdSb 2 with a Non-centrosymmetric Monoclinic Structure. Inorg Chem 2022; 61:10888-10897. [PMID: 35797442 DOI: 10.1021/acs.inorgchem.2c01354] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The Zintl phase Ca2CdSb2 was found to be dimorphic. Besides the orthorhombic Ca2CdSb2 (-o), here we report on the synthesis, the structural characterization, and the thermoelectric transport properties of its monoclinic form, Ca2CdSb2 (-m), and its Lu-doped variant Ca2-xLuxCdSb2 (x ≈ 0.02). The monoclinic structure exhibits complex structural characteristics and constitutes a new structure type with the non-centrosymmetric space group Cm (Z = 30). The electrical resistivity ρ(T) measured on single crystals of both phases portrays a transition from a semiconductor to a degenerate p-type semiconductor upon doping with Lu and with an attendant change in the Hall carrier concentration nH from 7.15 × 1018 to 2.30 × 1019 cm-3 at 300 K. The Seebeck coefficient S(T) of both phases are comparable and indicate a hole-dominated carrier transport mechanism with magnitudes of 133 and 116 μV/K at 600 K for Ca2CdSb2 (-m) and Ca2-xLuxCdSb2, respectively. The convoluted atomic bonding with an attendant large unit cell volume of ∼4365 Å3 drives a putative low thermal conductivity in these materials resulting in a power factor PF of 1.63 μW/cm K2 and an estimated thermoelectric figure of merit zT of ∼0.5 for Ca2-xLuxCdSb2 at 600 K. Differential scanning calorimetry results reveal the stability of these phases up to about 960 K, making them candidates for moderate temperature thermoelectric materials.
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Affiliation(s)
- Michael O Ogunbunmi
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Sviatoslav Baranets
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Svilen Bobev
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
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Liu D, Peng H, Sa R. Discovering the desirable physical properties of arsenic compounds AB 2As 2 and their alloys: a theoretical study. Phys Chem Chem Phys 2022; 24:26288-26296. [DOI: 10.1039/d2cp03333j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
The stability, elastic, electronic, and optical properties of AB2As2 (A = Ca, Sr; B = Mg, Zn, Cd) and their alloys with a trigonal CaAl2Si2-type structure are thoroughly examined for the first time based on the first-principles calculations.
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Affiliation(s)
- Diwen Liu
- School of Materials and Chemical Engineering, Pingxiang University, Pingxiang, 337055, China
| | - Huan Peng
- School of Materials and Chemical Engineering, Pingxiang University, Pingxiang, 337055, China
| | - Rongjian Sa
- College of Materials and Chemical Engineering, Minjiang University, Fuzhou 350108, China
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