Comparing the role of annealing on the transport properties of polymorphous AgBiSe2 and monophase AgSbSe2

Minmin Zou; Qing Liu; Chao-Feng Wu; Tian-Ran Wei; Qing Tan; Jing-Feng Li; Fei Chen

doi:10.1039/c7ra12819c

Comparing the role of annealing on the transport properties of polymorphous AgBiSe₂ and monophase AgSbSe₂

RSC Adv. 2018 Feb 13;8(13):7055-7061. doi: 10.1039/c7ra12819c. eCollection 2018 Feb 9.

Authors

Minmin Zou¹, Qing Liu^{1

2}, Chao-Feng Wu³, Tian-Ran Wei³, Qing Tan⁴, Jing-Feng Li³, Fei Chen¹

Affiliations

¹ School of Materials Science and Engineering, Beijing Institute of Petrochemical Technology Beijing 102617 China zouminmin@bipt.edu.cn.
² College of Materials Science and Engineering, Beijing University of Chemical Technology Beijing 100029 China.
³ State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University Beijing 100084 China.
⁴ State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing Beijing 100083 China.

Abstract

AgBiSe₂ and AgSbSe₂, two typical examples of Te-free I-V-VI₂ chalcogenides, are drawing much attention due to their promising thermoelectric performance. Both compounds were synthesized via melting and consolidated by spark plasma sintering. The role of annealing on the transport properties of polymorphous AgBiSe₂ and monophase AgSbSe₂ was studied. Annealing has a greater impact on AgBiSe₂ than AgSbSe₂, which is ascribed to the temperature dependent phase transition of AgBiSe₂. Unannealed AgBiSe₂ shows p-n switching, but annealed AgBiSe₂ exhibits n-type semiconducting behavior over the whole measurement temperature range. By performing high-temperature Hall measurements, we attribute this intriguing variation to the change in the amount of Ag vacancies and mid-temperature rhombohedral phase after annealing. Both AgBiSe₂ and AgSbSe₂ exhibit low thermal conductivity values, which are ∼0.40-0.50 W m^-1 K^-1 for AgSbSe₂ and ∼0.45-0.70 W m^-1 K^-1 for AgBiSe₂, respectively. The maximum ZT value of AgBiSe₂ is enhanced from 0.18 to 0.21 after annealing. Pristine AgSbSe₂ presents a ZT value as high as 0.60 at 623 K, although slight deterioration emerges after annealing.