Nagendra Singh Chauhan

Higher manganese silicides (MnSiγ), a class of Nowotny chimney-ladder (NCL) intermetallic compounds with complex incommensurate crystal structures, are promising candidates for realizing high-performance all-silicide thermoelectric modules. Herein, we explore quenching-induced structural disorder in melt-spun pseudo-binary Mn1–xCrxSi1.74 (0 ≤ x ≤ 0.20) compositions for hole concentration optimization and stabilization of high-temperature electronic transport. Incorporated Cr atoms into the [Mn] subsystem concomitantly modify the twisting pitch of the Si ladder while sustaining the incommensurate modulation. The Cr substitution increases the carrier concentration, which enhances the electrical conductivity significantly, leading to an improved power factor at high temperatures, while strain field effects from substitutional disorder lowered the lattice thermal conductivity (κL) ≈ 1.5 W m–1 K–1 synergistically, to improve the thermoelectric figure of merit (zT) ≈ 0.6 (±0.1) at 823 K for the bulk Mn0.92Cr0.08Si1.74 polycrystals. This work highlights the prospects of pseudo-binary transition-metal silicides for advancing p-type silicide thermoelectrics toward practical module integration in mid-temperature power generation applications.

Thermoelectric (TE) technology uses the Seebeck effect to directly convert heat into electricity or vice versa. Amongst its advantages are the lack of moving parts, reliability, absence of refrigerant gasses and scalability. To date, commercial progress has been limited due to relatively low conversion efficiencies and high costs. However, with increasing energy costs, the advent of the Internet of Things and its needs to power many sensors, and the need for thermal management in electronics, there is plenty of reason to be optimistic about the future of TE energy conversion. Beyond using abundant elements, sustainability has so far not been a major consideration in the development of TE technology, with its understandable emphasis on improving performance. However, sustainability aspects, including eco-friendly processing, resource efficient module fabrication, ensuring a long working life and end of life recycling should all be major considerations from the outset. This roadmap aims to provide an overview of current efforts moving towards sustainable TEs as well as guidance for future work. In terms of organization, the roadmap contains cross-cutting sections on aspects of sustainability and sections focused on the major TE materials. It can be read front to back or focusing on chapters of particular interest. We hope that this roadmap will stimulate new research, leading to the early adoption of sustainability concepts, beyond using abundant elements, in the development of large-scale TE technology.

Recent advances in polymer nanocomposites have opened promising routes for engineering carrier characteristics, phonon dynamics and conformational disorders, paving the way for next-generation thermoelectric materials. Herein, we report the development of free-standing, flexible films of Mg_0.99Cu_0.01Ag_0.97Sb_0.99 nanofiller-incorporated PANI:CSA polymer nanocomposites. The hybrid nanocomposites showed nearly a tenfold increase in the power factor and Seebeck coefficient, accompanied by a synergistic reduction (∼100%) in thermal conductivity, yielding a thermoelectric figure of merit (zT) of ∼0.13 (±0.02) at ∼300 K. Transport analysis employing the Kang–Snyder (KS) framework and Semi-Localized Transport (SLoT) modeling reveals an invariant scattering exponent in the semi-localized regime, implying preserved diffusive polaronic transport, improved interfacial connectivity, and energy-filtering-driven mobility enhancement, while structural and spectroscopic analyses reveal anisotropic lattice adaptation, dedoping-induced polaron stabilization, bond charge distribution, and preserved pseudo-orthorhombic order in PANI. To validate its practical applicability, a flexible thermoelectric generator was fabricated, producing an output voltage of ∼11.6 mV and underscoring the promise of Te-free, interface-engineered polymer–inorganic hybrids for wearable energy harvesting.

Designing zintl compounds with complex crystal structures and large unit cells containing heavy elements may inherit bonding heterogeneity‐induced lattice anharmonicity, leading to intrinsically low thermal conductivity. In this work, alloying‐induced bonding heterogeneity in the extensively explored α‐Mg₃(Sb, Bi)₂ phase due to local atomic ordering, site preferences, and prevailing heterogenous interfaces is evaluated in the p‐type Mg₃(Sb_1−2xBi_xSn_x)₂‐based polyanionic nanocomposites for different alloying concentrations. The inherent susceptibility for partial phase transition (trigonal → monoclinic) is observed upon alloying, which is driven by alterations in bonding patterns, localized distortion, and secondary phase formation. At low alloying content (x ≤ 0.05), a trigonal (Sb, Sn) phase is observed, while for higher alloying content (x ≥ 0.1), a cubic Mg₂Sn nanophase emerges. A synergistic reduction in thermal conductivity and enhanced power factor maximize the zT ≈ 0.25(±0.05) at 673 K in the optimized p‐type Mg₃(Sb_0.9Bi_0.025Sn_0.025)₂ nanocomposites. The study highlights bonding heterogeneity‐induced structural transitions as an inherent challenge, where the dominant role of anionic sites becomes pivotal for determining/deriving favorable structural and functional properties in Mg₃(Sb, Bi)₂‐based zintl compounds.

Unveiling superionic phase β-phase and off-centering dynamics of α-phase at higher temperature in Mg₃(Sb, Bi)₂ based Zintl compounds.