Research Highlights
Quasi-Random distribution of distorted nanostructures​
Specific explanations for high-entropy materials possessing superior thermoelectric properties were demonstrated. The basis of the findings lies in distorted nanostructures, where increased entropy is effectively applied to develop high-performance thermoelectric materials. The quasi-random distribution of distorted nanostructures (QDDN) was established using a multiple-element alloying approach. This approach signifies a significant step forward in the development of high-performance thermoelectric materials. The QDDN structure scatters strongly for different parts of the phonon spectrum, reducing the phonon group velocity. Reduced lattice thermal conductivity is confirmed by the Debye-Callaway model and density functional theory calculation.[Nano Energy, 112, 108493 (2023)]
Coated grained nanocomposites for coherent phonon transport
The designed coated grained nanocomposites are implemented to observe coherent phonon transport. The optimization of ZnO as a thermoelectric material is successfully demonstrated through the integration of a coated grain structure with doping. Al doping and ZnS coating in ZnO play crucial roles in introducing charged defects and enhancing coherent phonon scattering. This organized approach results in a remarkable (~62%) reduction in lattice thermal conductivity, achieved through improved phonon scattering. Consequently, a 272% enhancement in zT ~ 0.2 at 1073 K is attained in ZnS-coated Zn0.98Al0.020. It is noteworthy that this composition comprises toxic-free and abundant elements, showcasing a promising advancement in environmentally friendly thermoelectric materials.[Advanced Functional Materials, 31(43), 2105008 (2021)]
Large unit cell superionic compounds for thermoelectric applications
The work centers on selecting inherently poor thermal conductors and optimizing electrical transport to achieve high thermoelectric performance in superionic Argyrodites, with the potential for various substitutions and high ionic conductivities. Temperature-dependent thermoelectric studies are conducted across structural phase transitions, demonstrating that the cubic phase exhibits more efficient thermoelectric properties compared to the orthorhombic phase. Additionally, intriguing phenomena related to thermoelectric parameters, such as low-energy Einstein optical modes, are discussed for Argyrodite-based large unit cell superionic compounds.[ACS Applied Energy Materials, 2, 654 (2019)]
Crystalline anharmonicity and glassy thermal transport
Achieving partial control of charge carriers is possible through self-compensation by systematically filling vacancies with excess Sn. This research explores into distinctive concepts such as crystalline anharmonicity and glassy thermal transport, as well as electronic band convergence with doping, to enhance the thermoelectric performance of environmentally friendly crystalline bulk metal chalcogenides. The factors contributing to poor thermal conductivity, including point defect scattering, the presence of soft phonons, and impurity-localized modes, have been thoroughly understood and explained.[Applied Physics Letters, 109, 13, 133904 (2016)]
Effect of magnetic entropy with charge carriers
The study currently explores the magnetic and thermoelectric properties of Mn-doped, self-compensated Sn1.03Te, focusing on its dilute magnetic nature. Ongoing observations include a systematic increment in magnetic moments, an increase in the effective thermal mass of charge carriers, and overall enhancements in the power factor. This analysis is based on current findings from magnetization, anomalous Hall Effect, heat capacity, and high-temperature transport results in Sn1.03-xMnxTe.[Journal of Materials Chemistry C 6, 6489 (2018)]
Optimizing band convergence in SnTe through rare earth dopant incorporation
We emphasize that introducing a small amount of rare earth element doping can significantly improve the thermoelectric performance of SnTe, attributed to its heavy atomic mass and strong spin-orbit coupling. This improvement is achieved through effective valence band-convergence and an enhanced electronic density of states. The temperature-dependent transport data, along with first-principles calculations, provide support and justification for the increased power factor observed in SnTe with rare earth element doping.[Applied Physics Letters 113, 193904 (2018)]
Thermopower and Resistivity Measurement Setup
An automated setup for simultaneous measurement of thermopower and electrical resistivity has been developed and fabricated to operate within the temperature range of 85 to 600 K. This setup enables the mounting and measurement of samples with several geometrical shapes using a non-destructive method. The design of the sample holder has been accurately crafted to facilitate easy replacement of any damaged components. Thermopower measurements are conducted using the differential steady-state method, while electrical resistivity is determined employing the conventional four-probe technique. Pure nickel samples have been utilized to validate the accuracy and reliability of the setup.
