Ramesh Chandra Mallik

The Ta and Ni substitution in the Nb vacant NbCoSb compound increases the density of state effective mass and carrier concentration.

The crystal structure plays a crucial role in determining the thermoelectric performance of GeSe–GeTe alloys. Here, we investigate the effect of Bi substitution on phase stability and transport properties of rhombohedral GeSe0.5Te0.5. Bi incorporation induces a rhombohedral-to-cubic structural transition and stabilises the high-symmetry cubic phase near room temperature by reducing Peierls’ distortion, thereby addressing the structural instability associated with the high-temperature phase transition. Simultaneously, thermoelectric performance is enhanced, with Ge0.91Bi0.09Se0.5Te0.5 exhibiting a zTmax ~1.38 at 673 K. To elucidate the origin of the reduced lattice thermal conductivity, we combine experimental measurements with a machine-learning-assisted Green–Kubo framework. The calculations closely reproduce the experimental thermal transport behaviour and reveal enhanced lattice anharmonicity and soft phonon modes in the Bi-rich cubic phase, leading to strong phonon scattering and suppressed thermal conductivity. These findings establish phase stabilisation as an effective route for improving Ge-chalcogenide thermoelectrics.

Energy harvesting is gaining importance in the 21st century, with thermoelectric (TE) technology offering a promising method for converting thermal energy into electrical energy. However, the application of TE devices remains relatively low because of the limitations of conventional manufacturing methods. Fabricating complex-shaped TE devices using traditional manufacturing processes is challenging and leads to a low efficiency. Unlike conventional subtractive methods, additive manufacturing (AM) builds three-dimensional (3D) objects layer by layer, enabling the creation of intricate and complex structures with precision. This study explores recent trends in AM of thermoelectric systems, with a focus on materials, synthesis methods, and device fabrication. It also discusses the challenges associated with these AM techniques and explores potential areas for improvement. Recent studies have shown that AM can produce thermoelectric units with hollow and layered structures, enhancing temperature gradients and power density compared with conventional designs. The ability to customize geometries through AM offers promising opportunities to enhance the performance of the TE materials and devices. AM technologies can produce highly efficient, functionally graded TE devices. By enabling rapid prototyping and high-performance structures, AM can improve the efficiency and application of the TE materials. Future work focuses on further advancing these AM techniques by integration with machine learning (ML) and development of multimaterial TE devices.

Superionic conductors are a class of materials in which crystalline order is coupled with liquid-like ionic motion, producing an extreme anharmonic β-Cu ₂ Se lattice.

High-pressure torsion is used to attain grain refinement and introduce dense dislocations in BiCuSeO. The effect of HPT reduces the bandgap, increases carrier concentration and reduces κ to improve thermoelectric performance of BiCuSeO.

Thermal conductivity significantly depends on point defects and anharmonicity of the material, whose strength is given by the Grüneisen parameter ( γ ). In this work, apparent γ is calculated from the coefficient of thermal expansion and bulk modulus.

Copper selenide (Cu ₂ Se), a phonon liquid electron crystal (PLEC), is a promising thermoelectric material due to its efficient electron transport, but it suffers from copper ion migration, compromising its chemical stability.