A boost of thermoelectric generation performance for polycrystalline InTe by texture modulation

Current thermoelectric materials face limitations in efficiency due to trade-offs between electronic and thermal conductivity. While single-crystal materials often exhibit high performance, their cost and fragility hinder practical use. Polycrystalline materials offer mechanical robustness but typically suffer from grain boundary scattering that degrades electronic transport. Prior research has shown that texture modulation can align crystallographic directions to optimize transport properties. However, no prior work had resolved how to maintain texture in coarse-grained polycrystalline materials without significant grain boundary effects. This gap motivated the exploration of texture modulation in InTe, a promising binary material with anisotropic transport properties.

The aim of this work is to improve the thermoelectric performance of polycrystalline InTe by enhancing its texture along the [110] direction. The researchers propose that aligning crystallographic orientation can reduce grain boundary scattering while maintaining high electronic conductivity. They focus on the [110] direction because it exhibits both high electronic and low thermal conductivity. The study tests whether hot-deformation methods can produce coarse grains with high texture. The motivation stems from the need for robust, efficient thermoelectric materials that can be used in generator modules. The researchers also aim to demonstrate practical integration of InTe into a thermoelectric generator.

The researchers employed an oriented crystal hot-deformation method to fabricate coarse-grained InTe with a high degree of texture along the [110] direction. This process involves zone-melting and hot deformation to preserve crystal orientation. The resulting material was analyzed for texture using X-ray diffraction and electron backscatter diffraction. Electronic and thermal transport properties were measured via four-point probe and laser flash techniques. Mechanical properties were assessed using hardness and fracture toughness tests. The researchers also fabricated an 8-couple thermoelectric generator module using p-type InTe and n-type Bi₂Te₂.₇Se₀.₃. Performance was evaluated under a temperature gradient of 290 K.

The hot-deformation method produced InTe with a strong [110] texture and coarse grains. This texture reduced grain boundary scattering and preserved high electronic conductivity. The material achieved a room-temperature power factor of 8.7 μW cm⁻¹ K⁻¹, the highest reported for InTe. The average figure of merit reached 0.71 between 300 and 623 K. Mechanical properties improved due to the polycrystalline structure with refined grains. The 8-couple generator demonstrated a conversion efficiency of ~5.0% at 290 K. This efficiency is comparable to traditional Bi₂Te₃-based modules. The results suggest that texture modulation can enhance performance in polycrystalline materials. The study confirms that InTe is a viable candidate for room-temperature thermoelectric generation.

The authors state that texture modulation in InTe improves thermoelectric performance by reducing grain boundary scattering while maintaining anisotropic transport properties. They propose that the oriented hot-deformation method is effective for coarse-grained materials. The study demonstrates that high texture along the [110] direction leads to a high power factor and figure of merit. The researchers also suggest that the mechanical properties of InTe are enhanced by polycrystalline refinement. The integration into a generator module achieved efficiency comparable to traditional materials. The authors conclude that InTe is a promising candidate for room-temperature thermoelectric applications. They propose that texture modulation is a viable strategy beyond Bi₂Te₃ systems. The findings support further exploration of anisotropic materials for thermoelectric performance improvement.