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Aiming at exploring whether the Janus structure is beneficial to improving the thermoelectric (TE) performance, we systematically study the TE properties of the α -Se-monolayer-based Janus structures including α - SSe 2 and α - TeSe 2 monolayers. In comparison with the semiconducting α -Se monolayer, the Janus α - SSe 2 and α - TeSe 2 monolayers are still kept to be indirect semiconductors but with suppressed energy bandgaps. Moreover, the phononic thermal conductance will be suppressed with other parameters like Seebeck coefficients, electrical conductances, and electronic thermal conductances being changed correspondingly. The TE figures of merit Z T s of the Janus α - SSe 2 and α - TeSe 2 monolayers are always greater than that of the α -Se monolayer, indicating that the Janus structure should be a potential scheme used to improve the TE performance of materials. [ABSTRACT FROM AUTHOR]

Different from the extensive experimental investigations into the thermoelectric (TE) properties of the bulk IV–VI compounds, less attention has been paid to the TE properties of the monolayer IV–VI compounds. Here, we consider the TE transport properties including the Seebeck coefficient, electronic conductance, thermal conductance, power factor, and figure of merit Z T of the undoped and Bi-doped GeS monolayers. Our results show that for both the undoped and Bi-doped monolayers the anisotropy is widely observed in all their TE properties, and the maximum Z T at a certain temperature along the armchair direction is much greater than that along the zigzag direction. Moreover, Bi doping can lead to an increase of the maximum Z T , and there are more Z T peaks appearing near the zero chemical potential. This indicates that the Bi-doped GeS monolayer can work as a TE material at a lower bias voltage, and especially along the armchair direction it can work at zero bias voltage, which obviously strengthens the reliability of the TE devices. As the temperature increases, the maximum Z T will be uniformally increased along the armchair and zigzag directions for both the undoped and Bi-doped GeS monolayers. In the temperature scope from 300 to 800 K, the maximum Z T along the armchair direction of the Bi-doped GeS monolayer will increase from 3.39 to 4.85, which indicates that this Bi-doped GeS monolayer is a promising TE material in a wide-temperature zone. As an application, we have designed the GeS-based TE couples and found that their efficiencies can be greater than 27 % at large temperature differences. This research should be an important guidance for designing a low-voltage, wide-temperature-scope, and high-stability TE device. [ABSTRACT FROM AUTHOR]

With the increasing demand for energy, it has become imperative to investigate the thermoelectric properties that can be beneficial to directly converting heat into electric energy. Here, we theoretically study the thermoelectric transport of the Mn-doped blue phosphorene (blue-P) along the zigzag direction. We show that the spin-polarized electronic transport in the blue-P can be produced by the Mn-doping induced half-metallic energy band structure, and the Seebeck coefficients can take positive and negative values, indicating that the main carriers may be holes and electrons. Thus, the spin-down, spin, and charge Seebeck coefficients show a high peak and a deep valley, while the spin and charge thermoelectric figures of merit show two wide peaks. Moreover, the spin and charge thermoelectric figures of merit are found to be so large that the Mn-doped blue-P along the zigzag direction can be used as good thermoelectric materials. In addition, we consider the effect of the doping concentration on the electronic structure and thermoelectric transport properties. This research should be an important reference for designing spin caloritronic and thermoelectric devices. [ABSTRACT FROM AUTHOR]

The structural features, martensitic transformation, and magnetic domains in the Mn50Ni40Sn10 Heusler alloy are investigated by in-situ transmission electron microscopy and Lorentz microscopy. A rich variety of microstructural phenomena arising from structural and magnetic transitions are demonstrated at low temperatures. The '5M' or '6M' superstructure modulations and needle-shaped martensites have been clearly observed in the martensitic phase. Structural evolutions of magnetic domains are revealed under in-situ applied magnetic fields using Lorentz microscopy. The structural domains and reversibility of the phase transitions are analyzed based on our experimental observations and discussed in comparison with results of low-temperature magnetization. [ABSTRACT FROM AUTHOR]