Improved Thermoelectric Properties of BiSbTe-AgBiSe₂ Alloys by Suppressing Bipolar Excitation

Abstract

Bismuth telluride alloys are the only commercialized thermoelectric materials, which have successfully realized the practical applications of active cooling and waste heat harvesting near room temperature. However, the drawbacks of intermediate ZT values and brittle nature of zone-melted materials have limited their future development. Herein, we show that AgBiSe2 alloying is an effective approach to improve both the thermoelectric and mechanical performance of sintered Bi0.48Sb1.52Te3 materials. The addition of AgBiSe2 can not only suppress the bipolar effect by increasing the hole concentration but also decrease the lattice thermal conductivity by introducing various phonon scattering centers. These effects enable a peak ZT value of 1.1 at 375 K and an average value of 0.94 between 300 and 500 K in the composite of Bi0.48Sb1.52Te3-0.3 wt % AgBiSe2. Moreover, the addition of AgBiSe2 can also enhance the Vickers hardness, which reaches 0.75 GPa, 42% times higher than that of pristine zone-melted BiSbTe.

Highly Enhanced Thermoelectric and Mechanical Properties of Bi-Sb-Te Compounds by Carrier Modulation and Microstructure Adjustment

“…The calculation details are shown in the Supporting Information. In the +0.1 wt % sample, the κ lattice reaches 0.4 W/mK at 373 K, which is 0.27 W/mK lower than the value of 0.67 W/mK achieved at 323 K for the pure sample; the sample has an extremely low thermal conductivity compared to the value reported in previous studies. ,, The values of κ bipolar estimated from the calculated κ lattice are shown in Figure e. The value for the doped sample is 0.528, which is 17.3% lower compared to the value for the pure sample.…”

“…In the +0.1 wt % sample, the κ lattice reaches 0.4 W/mK at 373 K, which is 0.27 W/mK lower than the value of 0.67 W/mK achieved at 323 K for the pure sample; the sample has an extremely low thermal conductivity compared to the value reported in previous studies. 20,29,42 The values of κ bipolar estimated from the calculated κ lattice are shown in Figure 6e.…”

“…Tan et al 25 observed that the addition of second phase Cu 7 Te 4 increases the electrical conductivity and suppresses the bipolar effect, thus causing the temperature corresponding to the maximum ZT (1.14 at 444 K) to move toward the high-temperature region. Jiang et al 29 observed that the AgBiSe 2 second phase can put off the bipolar effect by increasing the carrier concentration (8.03 × 10 19 cm −3 ) and decrease the lattice thermal conductivity (0.65 W/m K) by enhancing various phonon scattering centers; the ZT value achieved was 1.1 at 357 K. Therefore, superionic conductor Cu 1.8 S may have a significant effect on BST.…”

“…To reduce the bipolar effect, it is necessary to regulate the carrier and band gap of the matrix material; this can be achieved by introducing hole carriers into the doping. The addition of hole carriers can be controlled by doping Cu, Pb, In, Ag, Mn, and Ca or by increasing the Sb content − and the addition of second phase Cu 7 Te 4 and AgBiSe 2 to introduce an energy filtering effect to increase the Seebeck coefficient. Tan et al observed that the addition of second phase Cu 7 Te 4 increases the electrical conductivity and suppresses the bipolar effect, thus causing the temperature corresponding to the maximum ZT (1.14 at 444 K) to move toward the high-temperature region.…”

Highly Suppressed Thermal Conductivity in Diamond-like Cu2SnS3 by Dense Dislocation

“…Good TE materials commonly have a high σ and S along with a low κ. In the past two decades, prominent progress has been made in decreasing the κ lat through strengthening phonon scattering by alloying, dislocations, , precipitates, and grain boundaries. , These methods suggest that microstructural modulation is crucial for optimizing the TE performance of a material.…”