The limited thermoelectric performance of p-type Higher Manganese Silicides (HMS) in terms of their low figure-of-merit (ZT), which is far below unity, is the main bottle-neck for realising an efficient HMS based thermoelectric generator, which has been recognized as the most promising material for harnessing waste-heat in the mid-temperature range, owing to its thermal stability, earth-abundant and environmentally friendly nature of its constituent elements. We report a significant enhancement in the thermoelectric performance of nanostructured HMS synthesized using rapid solidification by optimizing the cooling rates during melt-spinning followed by spark plasma sintering of the resulting melt-spun ribbons. By employing this experimental strategy, an unprecedented ZT ∼ 0.82 at 800 K was realized in spark plasma sintered 5 at% Al-doped MnSi HMS, melt spun at an optimized high cooling rate of ∼2 × 10 K s. This enhancement in ZT represents a ∼25% increase over the best reported values thus far for HMS and primarily originates from a nano-crystalline microstructure consisting of a HMS matrix (20-40 nm) with excess Si (3-9 nm) uniformly distributed in it. This nanostructure, resulting from the high cooling rates employed during the melt-spinning of HMS, introduces a high density of nano-crystallite boundaries in a wide spectrum of nano-scale dimensions, which scatter the low-to-mid-wavelength heat-carrying phonons. This abundant phonon scattering results in a significantly reduced thermal conductivity of ∼1.5 W m K at 800 K, which primarily contributes to the enhancement in ZT.

The synergistic effect of decoupled thermoelectric parameters on the enhanced power output of a unicouple TEG.

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In the present work, we propose an efficient thermoelectric cooler design for mitigating the cooling demand of high-end electronic components such as microprocessors, semiconductor lasers, etc. A 3D numerical model is developed using the finite element method (FEM) based commercial software COMSOL Multiphysics to investigate the effect of various geometric and operating parameters on the cooling performance of the thermoelectric cooler. The parameters such as fill factor, leg dimensions, heat sink size, and phase change material (PCM) filling pattern in the inter-fin spacings/gaps are optimized. Two heat sink PCM designs, M1 (alternate fin gaps filled) and M2 (all fin gaps filled), are investigated for hotspot mitigation. For no load conditions, the thermoelectric cooler module with a 20% fill factor produces a cooling of 20.5 °C with an average cooling per unit input power of 37.5°CW−1. When a heating load of 625 W/cm>2 is applied, its cold-side temperature reaches 91 °C. TEC module with n-eicosane PCM (M2 design) provides an effective cooling of 37 °C and an average cooling per unit input power of 42.3°CW−1. spacings/gaps are optimized. OM32 and n-eicosane were the two PCMs employed in the present study. The cold-side temperature reached 91 oC at the heating load of 625 W/cm2 when the thermoelectric cooler (TEC) device is switched OFF. The cold side temperature of the TEC dropped by 37 oC after 500 s at an input current of 7 A.