Thermoelectric performance of XI2 (X = Ge, Sn, Pb) bilayers

We study the thermal and electronic transport properties as well as the TE performance of three two-dimensional XI2 (X = Ge, Sn, Pb) bilayers using density functional theory and Boltzmann transport theory. We compared the lattice thermal conductivity, electrical conductivity, Seebeck coefficient, and dimensionless figure of merit (ZT) for the XI2 monolayers and bilayers. Our results show that the lattice thermal conductivity at room temperature for the bilayers is as low as ~1.1-1.7 Wm-1K-1, which is about 1.6 times as large as the monolayers for all the three materials. Electronic structure calculations show that all the XI2 bilayers are indirect-gap semiconductors with the band gap values between 1.84 eV and 1.96 eV at PBE level, which is similar as the corresponding monolayers. The calculated results of ZT show that the bilayer structures display much less direction dependent TE efficiency and have much larger n-type ZT values compared with the monolayers. The dramatic difference between the monolayer and bilayer indicates that the inter-layer interaction plays an important role in the TE performance of XI2, which provides the tunability on their TE characteristics.

Bipolar doping and thermoelectric properties of Zintl arsenide Eu5In2As6

Zintl compounds exhibit promising thermoelectric properties because of the feasibility of the chemical tuning of their electrical and thermal transport. While most Zintl pnictides are known to show p-type polarity, recent developments in high-performance n-type Mg3Sb2-based thermoelectric materials have encouraged further identification of n-type Zintl pnictides. In this study, we demonstrate the bipolar dopability of the Zintl arsenide Eu5In2As6. The electrical resistivity at 300 K with n-type polarity was decreased to 7.6 x 10^-1 ohmcm using La as an electron dopant. In contrast to the relatively high resistivity of n-type Eu5In2As6, the p-type resistivity at 300 K was decreased to 5.9 x 10^-3 ohmcm with a carrier concentration of 2.8 x 10^20 /cm3 using Zn as a hole dopant. This doping asymmetry is discussed in terms of the weighted mobility of electrons and holes. Furthermore, a very low lattice thermal conductivity of 0.7 W/mK was observed at 773 K, which is comparable to that of the Sb-containing analogue Eu5In2Sb6. The dimensionless figure of merit ZT = 0.29 at 773 K for Zn-doped p-type Eu5In2As6. This study shows that bipolar dopable Eu5In2As6 can be a platform to facilitate a better understanding of the doping asymmetry in Zintl pnictides.

Performance evaluation of thermoelectric generators under cyclic heating

The effect of thermal cycling on thermoelectric generator (TEG) performance is investigated for six nominally identical samples subjected to the same heating cycle profile. All TEGs experienced performance degradation, with maximum power outputs between 28 % and 49 % of pre-cycling values and a post-cycling decrease in the dimensionless figure of merit ZT of 21 % to 49 %. Sudden significant power reductions and subsequent internal resistance increases were observed for all samples, indicative of internal damage to the structure of the TEGs arising from material interface separation and micro-crack formation.

The efficiency of short sintering time on thermoelectric properties of delafossite CuCr0:85Mg0:15O2 ceramics

Introduction: Harvesting the waste heat emitted from the activities of humanity based on thermoelectric devices is an appropriate way to reduce the overconsumption of fossil fuel nowadays. Methods: In this work, CuCr0:85Mg0:15O2 compounds prepared by conventional solid-state reaction method were investigated to find out that the short sintering time is enough for thermoelectric applications, directly low the cost of the devices. Results and Conclusion: We find out that there is a significant change in the crystal structure, the chemical state, and thermoelectric properties along with the increase of the sintering time, but eventually, the dimensionless figure of merit ZT is almost constant regardless of the long or short sintering time which means that the increase of electrical conductivity will compromise the increase of thermal conductivity. The highest ZT value is 0.03 measured at 500 oC for both samples prepared at the sintering time of 3 and 12 hours.

Thermoelectric Properties of the As/P-Based Zintl Compounds EuIn2As2−xPx (X = 0 to 2) and SrSn2As2

Zintl compounds containing Sb have been studied extensively because of their promising thermoelectric properties. In this study, we prepared As/P-based Zintl compounds, EuIn2As2-xPx (x = 0 to 2) and SrSn2As2, and examined their potential for use as thermoelectric materials. These compounds show hole carrier concentrations of ~10^19 /cm3 for EuIn2As2-xPx and ~10^21 /cm3 for SrSn2As2 at 300 K. The high carrier concentration of SrSn2As2 is likely owing to self-doping by hole-donating Sn vacancies. The electrical power factor reaches ~1 mW/mK2 at ~600 K for EuIn2As2-xPx with x = 0.1 and 0.2. The lattice thermal conductivity is determined to be 1.6–2.0 W/mK for EuIn2As2 and SrSn2As2, and 2.8 W/mK for EuIn2P2 at 673 K. The dimensionless figure of merit reaches ZT = 0.29 at 773 K for EuIn2As2-xPx with x = 0.2. First-principles calculations show that EuIn2As2 and SrSn2As2 are topologically nontrivial materials with band inversion, while EuIn2P2 is a conventional semiconductor with a bandgap. The present study demonstrates that As/P-based Zintl compounds can also show promising thermoelectric properties, thus expanding the frontier for efficient thermoelectric materials.

Thermoelectric Properties of the As/P-Based Zintl Compounds EuIn2As2−xPx (X = 0 to 2) and SrSn2As2

Zintl compounds containing Sb have been studied extensively because of their promising thermoelectric properties. In this study, we prepared As/P-based Zintl compounds, EuIn2As2-xPx (x = 0 to 2) and SrSn2As2, and examined their potential for use as thermoelectric materials. These compounds show hole carrier concentrations of ~10^19 /cm3 for EuIn2As2-xPx and ~10^21 /cm3 for SrSn2As2 at 300 K. The high carrier concentration of SrSn2As2 is likely owing to self-doping by hole-donating Sn vacancies. The electrical power factor reaches ~1 mW/mK2 at ~600 K for EuIn2As2-xPx with x = 0.1 and 0.2. The lattice thermal conductivity is determined to be 1.6–2.0 W/mK for EuIn2As2 and SrSn2As2, and 2.8 W/mK for EuIn2P2 at 673 K. The dimensionless figure of merit reaches ZT = 0.29 at 773 K for EuIn2As2-xPx with x = 0.2. First-principles calculations show that EuIn2As2 and SrSn2As2 are topologically nontrivial materials with band inversion, while EuIn2P2 is a conventional semiconductor with a bandgap. The present study demonstrates that As/P-based Zintl compounds can also show promising thermoelectric properties, thus expanding the frontier for efficient thermoelectric materials.

Environmentally friendly thermoelectric sulphide Cu2ZnSnS4 single crystals with dimensionless figure of merit ZT achieving 1.6

Thermoelectrics (TEs) are an important class of technologies for harvesting electric power directly from heat sources. To design both high performance and environmentally friendly for TE materials, pseudo-cubic structure has...