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IV–VI Compounds for Medium Temperatures
Published in Zhifeng Ren, Yucheng Lan, Qinyong Zhang, Advanced Thermoelectrics, 2017
Qian Zhang, Yu Xiao, Li-Dong Zhao, Eyob Chere, Zhifeng Ren, Xiao Zhang, Cheng Chang, E. M. Levin
Tin selenide crystallizes in a layered orthorhombic crystal structure with lattice parameters a = 11.49 Å, b = 4.44 Å, c = 4.135 Å,164 which can be considered as layered distorted rock salt structure. Figure 4.49 shows the perspective views of the room-temperature SnSe crystal structure along the a, b, and c axial directions. The unit cell with eight atoms consists of double two atom-thick layers, which form the zigzag structure. Each layer can be viewed as consisting of six-membered rings in chair conformation.165 The Sn and Se atoms are bonded with strong covalent bonds within the layers which are perpendicular to the c axis, while atoms in different layers are linked with weak force along the c axis.166 Due to the highly layered structure, tin selenide cleave easily along the (001) plane. The structure contains highly distorted SnSe7 coordination polyhedrons, which consists of three short Sn–Se bonds and four long Sn–Se bonds and a lone pair of the Sn2+ sterically accommodated between the four long Sn–Se bonds.164,167 The previous investigations indicate that there is a displacive reversible phase transition in SnSe from the orthorhombic structure (Pnma) to the orthorhombic structure (Cmcm) at ~750–800 K.164,168,169 This phase transition can also be observed in SnSe bulks in the constant high pressure environment (~7 GPa)170 and SnSe nanocrystals at room temperature.171
A comprehensive review of solar, thermal, photovoltaic, and thermoelectric hybrid systems for heating and power generation
Published in International Journal of Green Energy, 2023
Ali Faddouli, Mohammed Hajji, Salah Fadili, Bouchaib Hartiti, Hicham Labrim, Abderrahim Habchi
In large terms, TE materials can be divided into three categories: inorganic, organic, and inorganic/organic (hybrids). Materials constructed of inorganic compounds fall under the first group. Examples include silicon germanium (SiGe), tin selenide (SnSe), lead telluride (PbTe), and bismuth telluride (BiTe). The second group is constructed of TE materials and mostly uses conductive polymers as its active material, for example poly(3,4-ethylen-edioxy-thiophene):poly (styrenesul-fonate) (PEDOT,PSS), polyaniline (P,ANI) and poly-pyrrole (PPY). Third, hybrid TE group, which consist of an inorganic material (metal-based chemicals) as an adjunct, injected into an organic material as a binder. For instance, BiTe:PEDOT:PSS is a hybrid TE material made of a polymer conductor and an inorganic metal alloy. While there are TE materials widely used in laboratories with a figure of merit ZT of 2, nonetheless, the desired ZT value is 3 or above (Jin et al. 2019). Table 3 summarizes the TE materials applicable to sleek TEGs according to their categories.