123rd General Meeting of the KCS

Type Oral Presentation
Area Oral Presentation of Young Inorganic Chemists
Room No. Room 401+402
Time THU 10:20-10:30
Code INOR.O-9
Subject Zintl Phase Thermoelectric Material with the n-type dopant: Ca5-x-yYbxREyAl2Sb6
Authors Seungeun Shin, Tae-Soo You*
Department of Chemistry, Chungbuk Natioanl University, Korea
Abstract Thermoelectric (TE) materials and the devices based on these materials have been considered as one of the smartest approaches to reduce global energy consumption by recovering the wasted heat from various heat sources and converting it into electricity. Recently, the A5M2Pn6 (A = Ca, Sr, Eu, Yb; M = Al, Ga, In) series has been extensively investigated as Zintl phase TE materials, and two major structure types have been identified: the Ba5Al2Bi6-type having metallic behavior and the Ca5Ga2Sb6-type showing the semiconducting behavior. To investigate the effect of cationic substitution and n-type doping for TE properties of the Ca5Ga2Sb6-type compounds, a quinary Zintl phase Ca3.21(1)Yb1.65Pr0.15Al2Sb6 was successfully synthesized by arc-melting, and its crystal structure was characterized by both powder and single-crystal X-ray diffractions. It has been known that in the Ca5-xYbxAl2Sb6 (1.0 ≤ x ≤ 5.0) system, the Ca-rich compound adopts the Ca5Ga2Sb6-type structure whereas the Ba-rich compound adopts the Ba5Al2Bi6-type structure. Nevertheless, the Ca-rich rare-earth containing title compound adopted the Ba5Al2Bi6-type with the orthorhombic space group Pbam (Z=2, Pearson Code oP26) after the initial arc-melting and the post heat treatment transformed to the Ca5Ga2Sb6-type structure. According to the SXRD result, only one cationic site contains the n-type dopant RE3+ with a particular site-preference. In addition, the thermoelectric property measurement implies that the initial Ba5Al2Bi6-type compound was p-type, while the Ca5Ga2Sb6-type compound was the n-type TE material. To understand the interesting TE property transition from the p-type to the n-type character, a series of theoretical calculations using three hypothetical models by tight-binding linear muffin-tin orbital method were performed, and the results were thoroughly analyzed.
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