Synergistic Effect of Work Function and Acoustic Impedance Mismatch for Improved Thermoelectric Performance in GeTe-WC Composite

Abstract

The preparation of composite materials is a promising methodology for concurrent optimization of electrical and thermal transport properties for improved thermoelectric (TE) performance. This study demonstrates how the acoustic impedance mismatch (AIM) and the work function of components decouple the TE parameters to achieve enhanced TE performance of the (1-z)Ge 0.87 Mn 0.05 Sb 0.08 Te-(z)WC composite. The simultaneous increase in the electrical conductivity (σ) and Seebeck coefficient (α) with WC (tungsten carbide) volume fraction (z) results in an enhanced power factor (α 2 σ) in the composite. The rise in σ is attributed to the creation of favorable current paths through the WC phase located between grains of Ge 0.87 Mn 0.05 Sb 0.08 Te, which leads to increased carrier mobility in the composite. Detailed analysis of the obtained electrical properties was performed via Kelvin probe force microscopy (work function measurement) and atomic force microscopy techniques (spatial current distribution map and current−voltage (I−V) characteristics), which are further supported by density functional theory (DFT) calculations. Furthermore, the difference in elastic properties (i.e., sound velocity) between Ge 0.87 Mn 0.05 Sb 0.08 Te and WC results in a high AIM, and hence, a large interface thermal resistance (R int ) between the phases is achieved. The correlation between R int and the Kapitza radius depicts a reduced phonon thermal conductivity (κ ph ) of the composite, which is explained using the Bruggeman asymmetrical model. Moreover, the decrease in κ ph is further validated by phonon dispersion calculations that indicate the decrease in phonon group velocity in the composite. The simultaneous effect of enhanced α 2 σ and reduced κ ph results in a maximum figure of merit (zT) of 1.93 at 773 K for (1z)Ge 0.87 Mn 0.05 Sb 0.08 Te-(z)WC composite for z = 0.010. It results in an average thermoelectric figure of merit (zT av ) of 1.02 for a temperature difference (ΔT) of 473 K. This study shows promise to achieve higher zT av across a wide range of composite materials.

Enhanced Thermoelectric Performance of GeTe-Based Composites Incorporated with Fe Nanoparticles

“…Single-phase alloys have been well studied with five times the number of publications on multiphase/composite TE materials, but investigating composites is one of the most viable strategies to enhance thermoelectric performance by designing new materials . Constructing suitable nanostructures to optimize the electronic and thermal transport properties simultaneously is widely used in the GeTe-based system, such as superlattices, , stacking faults, dislocation arrays, in situ nanoprecipitates, , and ex situ nanophases. − …”

Boosting Thermoelectric Performance in Nanocrystalline Ternary Skutterudite Thin Films through Metallic CoTe2 Integration

“…However, thermoelectric performance of thin film counterpart does not align with their bulk form due to different fabrication process lead to dissimilar electronic and thermal transport properties . To enhance the thermoelectric properties of thin films, developing metal–semiconductor (M–Sc)-based composites offers a viable approach, extensively researched in the bulk forms of various thermoelectric materials. − These composites effectively boost the electrical conduction through mechanisms such as carrier channeling, and carrier injection simultaneously suppresses phonon conduction by enhancing interfacial phonon scattering to achieve enhanced thermoelectric performance. ,, The influence of the metallic phase on σ is contingent upon the band structure of the matrix, the potential energy barrier at the interface between the two phases, and the electrical and thermal transport properties of the metallic phase. Also, the morphology, amount, and physical characteristics of the guest phase play a critical role in determining the resulting thermoelectric transport properties. ,− Previous studies had demonstrated the effect of metallic nanostructures in TE materials like (Bi,Sb) 2 (Te,Se) 3 , CoSb 3 , and MnSi 1.787 Al 0.0138 , where the selection of metallic inclusions with distinct work functions provides the perspective of a tunable barrier at the interface, promoting the electronic transport to tailor the TE properties.…”

Rashba and Dresselhaus effects in doped methylammonium lead halide perovskite MAPbI3

“…Doping has been extensively studied in literature with the aim of reducing the presence of toxic elements and enhancing the properties of compounds. [50][51][52][53] Therefore, in this study, we have substituted Pb with Sn and Ge in the MAPbI 3 perovskite. Another method for reducing Pb content is by introducing Pb-vacancies in the compound, however, it is worth noting that such vacancies are not stable.…”