Study of Phase Formation Behavior and Electronic Transport Properties in the FeSe2 -FeTe2 System

Abstract

In this study, we investigated the phase formation behavior of the FeSe2-FeTe2 system and the evolution of their thermoelectric transport properties. A series of Fe(Se1-xTex)2(x = 0, 0.2, 0.6, 0.8 and 1) compounds were synthesized by conventional solid-state reaction. Single phase orthorhombic structures were formed, except for FeSe0.4Te1.6(x = 0.2). For FeSe0.4Te1.6(x = 0.2), in which a mixture of FeSe2 and FeTe2-based phases was observed. The electrical conductivity of FeSe2 was as low as 31 S/cm at room temperature, and greatly increased to 1295 S/cm in FeSe0.8Te1.2. Then it decreased to 335 S/cm for FeTe2. It was shown that the bipolar conduction of electrons and holes pronouncedly exists in the sample. For FeSe2 and FeTe2, the Seebeck coefficient was positive at room temperature, becoming negative at high temperatures. For the other samples, the Seebeck coefficient was negative at room temperature and the magnitude of Seebeck coefficient increased with temperature. As results, the maximum power factor of 0.19 mW/mK2 was observed for FeSe0.8Te1.2(x = 0.6) at room temperature mostly due to its high electrical conductivity. The maximum power factor observed at 600 K was 0.34 mW/mK2 for FeSe2 (x = 0) with the largest Seebeck coefficient of -101 µV/K. The Hall carrier concentration was measured and compared, and effective masses were calculated to further investigate electrical transport in the samples.

Electrical, Thermal, and Thermoelectric Transport Properties of Co-Doped <i>n</i>-type Cu_0.008Bi₂Te_2.6Se_0.4 Polycrystalline Alloys

“…Defect engineering, such as doping, addition, and solidsolution, are the most used strategies for reducing κ latt by promoting point defect phonon scattering [16][17][18][19]. Doping strategies have been widely applied to enhance the thermoelectric transport properties of thermoelectric materials, particularly the n-type Bi 2 Te 3 -based alloys [19][20][21][22].…”

Thermodynamics and robust n-type charge carrier density in Co-doped FeTe2: strain strategy

“…It is experimentally observed that FeTe 2 crystal has an antiferromagnetic lowest energy phase with anisotropic behavior <∼80 K and a ferromagnetic (FM) state <30 K [10]. Additionally, FeTe 2 system exhibits bipolar conduction, which means that main carrier switches at a certain temperature, resulting in poor thermometric performance [12,13]. Moreover, An et al experimentally studied the impact of Ni doping on electrical and thermal properties of FeTe 2 , and found an increase in electrical conductivity with increasing temperature [14].…”

Phase Formation Behavior and Thermoelectric Transport Properties of S-Doped FeSe2−xSx Polycrystalline Alloys

“…FeSe 2 is known to be thermally and structurally stable, as previous studies have reported [16,17]. It has a high carrier concentration, of 10 18 -10 19 cm −3 , and is considered a good candidate for thermoelectric applications [17,18]. FeS 2 is a semiconductor with a narrow bandgap (~1 eV) and is one of the most abundant sulfides in the Earth's crust [19].…”