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Title: Role of Eu-Doping in the Electron Transport Behavior in the Zintl Thermoelectric Ca5-x-yYbxEuyAl2Sb6 System

Journal Article · · Chemistry of Materials
 [1];  [1]; ORCiD logo [2];  [1];  [3]; ORCiD logo [4]; ORCiD logo [3];  [1];  [2]; ORCiD logo [5]; ORCiD logo [1]
  1. Chungbuk National University (Korea, Republic of)
  2. Ames Lab., and Iowa State Univ., Ames, IA (United States)
  3. Sogang Univ. Seoul (Korea, Republic of)
  4. Pohang Accelerator Lab. (PAL) (Korea, Republic of)
  5. Iowa State Univ., Ames, IA (United States)
+ Show Author Affiliations

A series of Eu-doped Zintl compounds belonging to theCa5-x-yYbxEuyAl2Sb6 (x = 0, 1.12; 0 ≤ y ≤ 0.63(2)) system have been successfully synthesized by both the arc-melting and the molten Pb-flux methods. All of the five title compounds initially crystallized in the Ca5Ga2As6-type phase (space group Pbam, Z = 2, Pearson code oP26) and maintained their original structure even after the post-heat treatment, unlike the recently reported n-type Zintl analogues in the Ca5-x-yYbxREyAl2Sb6 (RE = Pr, Nd, Sm) systems, which underwent a phase transition from the Ca5Ga2As6-type to the Ca5Al2Bi6-type phase after annealing. This research aimed to understand the origin of the structural preference of the title Ca5-x-yYbxEuyAl2Sb6 system, whether it was affected by the valence electron count or the cationic size. Electrical transport property measurements showed an increase in electrical conductivities and a decrease of Seebeck coefficients for Ca4.89(1)Eu0.11Al2Sb6, Ca4.82(1)Eu0.18Al2Sb6, and Ca4.62(1)Eu0.38Al2Sb6, compared to the parental compound Ca5Al2Sb6. Hole effect measurements proved that these changes should be attributed to the reduced carrier concentration and enhanced carrier mobility. The comprehensive density functional theory calculations including electron density map analysis for the hypothetical model Ca4.5Eu0.5Al2Sb6 revealed that the polarity between Al and Sb forming the anionic frameworks decreased as the Eu-dopants were introduced, which eventually affected the carrier mobility in the anionic frameworks. Thermal conductivity measurements proved that the Eu-doping successfully lowered the lattice thermal conductivity because of the enhanced atomic disordering. In conclusion, the magnetization measurements for Ca4.37(2)Eu0.63Al2Sb6 showed a typical Curie–Weiss behavior with weak antiferromagnetic nearest-neighbor interactions with θp = -5.07 K.

Research Organization:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division (MSE); National Research Foundation of Korea (NRF)
Grant/Contract Number:
AC02-07CH11358; SC0022288; 2021R1A2C1003661; 2019R1A2C3005530
OSTI ID:
2202976
Report Number(s):
IS-J-10,943
Journal Information:
Chemistry of Materials, Vol. 34, Issue 22; ISSN 0897-4756
Publisher:
American Chemical Society (ACS)Copyright Statement
Country of Publication:
United States
Language:
English

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Related Subjects

36 MATERIALS SCIENCE
Crystal structure
Diffraction
Metals
Phase transitions
Thermal conductivity