Doping-Induced Polymorph and Carrier Polarity Changes in Thermoelectric Ag(Bi,Sb)Se2 Solid Solution

Kenta Sudo; Yosuke Goto; Ryota Sogabe; Kazuhisa Hoshi; Akira Miura; Chikako Moriyoshi; Yoshihiro Kuroiwa; Yoshikazu Mizuguchi

doi:10.1021/acs.inorgchem.9b01038

Doping-Induced Polymorph and Carrier Polarity Changes in Thermoelectric Ag(Bi,Sb)Se₂ Solid Solution

Inorg Chem. 2019 Jun 3;58(11):7628-7633. doi: 10.1021/acs.inorgchem.9b01038. Epub 2019 May 10.

Authors

Kenta Sudo¹, Yosuke Goto¹, Ryota Sogabe¹, Kazuhisa Hoshi¹, Akira Miura², Chikako Moriyoshi³, Yoshihiro Kuroiwa³, Yoshikazu Mizuguchi¹

Affiliations

¹ Department of Physics , Tokyo Metropolitan University , Hachioji 192-0397 , Japan.
² Faculty of Engineering , Hokkaido University , Kita-13, Nishi-8 , Kita-ku, Sapporo , Hokkaido 060-8628 , Japan.
³ Department of Physical Science , Hiroshima University , 1-3-1 Kagamiyama , Higashihiroshima , Hiroshima 739-8526 , Japan.

PMID: 31074617
DOI: 10.1021/acs.inorgchem.9b01038

Abstract

Silver bismuth diselenide (AgBiSe₂) is an n-type thermoelectric material that exhibits a complex structural phase transition from the hexagonal to cubic phase, while silver antimony diselenide (AgSbSe₂) is a p-type thermoelectric material that crystallizes in the cubic phase at all temperatures. Here, we investigate the crystal structure and thermoelectric properties of Ag(Bi,Sb)Se₂ solid solution, employing AgBi_0.9Sb_0.1Se₂ and AgBi_0.7Sb_0.3Se₂ as representative samples. The carrier polarity of AgBi_0.9Sb_0.1Se₂ is converted from the n-type to p-type by Pb doping, accompanied by a polymorphic change to the cubic phase. It is difficult to obtain highly conductive p-type hexagonal AgBiSe₂-based materials, although first-principles calculations predict high-performance thermoelectric properties for these systems. We also demonstrate that cubic AgBi_0.7Sb_0.3Se₂ undergoes a polymorphic change to the hexagonal phase upon Nb doping. The present study show that polymorphic changes inevitably occurred upon Pb/Nb doping to optimize thermoelectric properties of Ag(Bi,Sb)Se₂ solid solution.