Low-Temperature Thermoelectric Properties of β-Ag2Se Synthesized by Hydrothermal Reaction

Abstract

b-Ag 2 Se is a narrow-bandgap semiconductor with a high electrical conductivity, reasonably large Seebeck coefficient, and low thermal conductivity. It is regarded as a potential candidate for thermoelectric applications. In this work, we prepared powders of b-Ag 2 Se by hydrothermal reaction at 180°C. The spark plasma sintering technique was employed to form compact samples. The thermoelectric properties were measured in a temperature range between 20 K and 350 K. A maximum figure of merit of over 0.6 was found around room temperature. Theoretical calculations were carried out to estimate the Seebeck coefficient of b-Ag 2 Se, reproducing the experimental trend qualitatively.

High thermoelectric efficiency in electrodeposited silver selenide films: from Pourbaix diagram to a flexible thermoelectric module

“…5 in red triangles) was found to be -136 ± 14, -94 ± 9, -107 ± 11, -112 ± 11, and -118 ±12 μV/K for 0.084, 0.078, 0.071, 0.044, and -0.015 V, respectively. The maximum Seebeck coefficient of -136 ± 14 was observed for the film grown at 0.084 V. The Seebeck coefficient values obtained in this study are similar to the values found in the literature for bulk silver selenide [20][21][22][23]26 and films 24,25 . The maximum value in this magnitude (-180 μV/K at RT) found in the literature was obtained in thin films grown by sputtering 19 .…”

“…However, two years ago, silver selenide thin films were developed 19,24,25 . These materials were obtained using spark plasma sintering (SPS) 22,26 , ball-milling process 27 , microwaveassisted solution 28 , hot pressing 21 , Pulsed Hybrid Reactive Magnetron Sputtering (PHRMS) 19 , or vacuum-assisted infiltration 24,25 . The thermoelectric properties of silver selenide grown by these techniques were studied.…”

“…In addition, the thermal conductivity is very low in both cases, with values between 1.5 21 and 0.64 W/m•K 19 . These thermoelectric properties result in a figure of merit between 0.6 26 and 1.2 19 at room temperature. These high values of zT at room temperature makes this material of interest for room temperature applications.…”

Thermoelectric transport of Se-rich Ag2Se in normal phases and phase transitions

“…This is consistent with the literature. [15][16][17] Thus, the band gap (E g ) in a semiconductor under intrinsic state is described by 18 Table I. They are 0.20 eV 6 15%, which is comparable with the previous studies.…”

“…In addition, due to its low band gap ($0.2 eV) 11,12 which is similar to Bi 2 Te 3 , 13 Ag 2 Se is expected to show the maximum zT values around room temperature. Experimentally, it has been demonstrated that Ag 2 Se has high r, moderate S, and small j by a handful of recent literature, [14][15][16] in which the researchers mainly focused on the low temperature TE transport. A maximum zT of 0.96 at 300 K is reported only by Ferhat and Nagao.…”