Thermoelectric Transport Properties of Cd_xBi_yGe_1–x–yTe Alloys

Abstract

Band convergence has been proven as an effective approach for enhancing thermoelectric performance, particularly in p-type IV–VI semiconductors, where the superior electronic performance originates from the contributions of both L and Σ band valleys when they converge to have a small energy offset. When alloying with cubic IV–VI semiconductors, CdTe has been found as an effective agent for achieving such a band convergence. This work focuses on the effect of CdTe-alloying on the thermoelectric transport properties of GeTe, where the carrier concentration can be tuned in a broad range through Bi-doping on Ge site. It is found that CdTe-alloying indeed helps to converge the valence bands of GeTe in both low-T rhombohedral and high-T cubic phases for an increase in Seebeck coefficient with a decrease in mobility. In addition, the strong phonon scattering due to the existence of high-concentration Cd/Ge and Bi/Ge substitutions leads the lattice thermal conductivity to be reduced to as low as 0.6 W/(m-K). These lead to an effectively increased average thermoelectric figure of merit (ZT ave ∼ 1.2) at 300–800 K, which is higher than that of many IV–VI materials with CdTe-alloying or alternatively with MnTe-, MgTe-, SrTe-, EuTe-, or YbTe-alloying for a similar band convergence effect.

Superhydrophobic polyimide aerogels via conformal coating strategy with excellent underwater performances

“…The surface structure of the PI aerogel was smooth and flat, which may lead to decrease of contact angle. 33 Nevertheless, the surface structure of the F-PI aerogel was destroyed, the inside porous structure of the F-PI aerogel was partially preserved [ Figure S15(d)]. These results also confirmed that even the F-PI aerogel was presented in a depth of ca.…”

“…In addition, the F-PI aerogels exhibited self-cleaning performance similar to the lotus effect. 33 As shown in the Supporting Information of Figure S3, the dust on the aerogel surfaces could be easily washed away by water.…”

“…As illustrated in Figures 1 and S1, the PI aerogel derived from poly(PPDA-BPADA) and poly(DMBZ-BPDA) was first prepared by the conventional route, which involved sol-gel transition and supercritical CO 2 drying. 33 Subsequently, the PI aerogel was directly immerged into a fluorocarbon resin (FR) solution to coat a hydrophobic FR layer on the surface of PI nanofibrous skeleton. Then a series of F-PI aerogels with high contact angle (CA up to 156 ) and excellent water-resistant property were prepared.…”

“…Du et al 31 reported a series of hydrophobic of PI aerogels by physical blending method via the dispersion of superhydrophobic silica aerogel powders in the PI matrix. Zhang et al 33 reported superhydrophobic PI aerogels prepared by a self-segregation method via introducing bio-inspired structures (a method beyond the chemical hydrophobilization), resulting a contact angle up to 152 (see Supporting Information Figure S1). However, most of the hydrophobilization methods are either too complicated or sacrificing of the mechanical and thermal properties of the corresponding PI aerogels.…”

Low‐Energy GeP Monolayers with Natural Type‐II Homojunctions for SunLight‐Driven Water Splitting

“…[27,28] Also, those with further suitable band-edge positions are highly expected for sunlight-driven water-splitting as efficient photocatalyst [29][30][31] due to their high surface ratio. Binary alloys of group IV-V elements (AB, A═Si, Ge and B═P, As) adopting layered structures [32][33][34] provide us another family of 2D materials. Based on the well-known top-to-down synthesizing strategy, few-layered group IV-V compounds have been experimentally realized.…”