Single crystal growth & design
















       Our laboratory is dedicated to advancing the understanding of fundamental electrical, optical, and thermal transport properties of novel materials by developing and refining a range of single-crystal growth techniques. These include the Bridgman method, solution-based growth methods, and other specialized techniques tailored for producing high-quality crystals. By mastering these approaches, we aim to explore the intrinsic properties of materials with unparalleled precision. We invite collaborators and researchers who share a keen interest in large single-crystal growth and characterization to join us in pushing the boundaries of material science and solid-state physics.

Developing high-performance thermoelectric materials





    
                                                                                 

DOI:10.1051/e3sconf/20171401032,  DOI:10.3390/app9071511
        The escalating global energy demand, coupled with growing environmental concerns over fossil fuel usage, has driven an intense wave of research into alternative energy technologies. Among these, thermoelectric (TE) technologies have emerged as particularly promising due to their ability to directly convert heat into electricity. TE devices are crafted from degenerate semiconductors or semimetals, collectively known as TE materials. The efficiency of a TE material at a given temperature T s measured by its dimensionless figure of merit, zT = σS2T/κ, where σ, S, and κ are the electrical conductivity, Seebeck coefficient, and thermal conductivities, respectively.While there is no known theoretical upper limit for zT, state-of-the-art TE materials typically achieve a maximum zT below 3.0. This limitation arises from the intrinsic trade-offs among {σ, S, κ}. Consequently, the energy conversion efficiency of existing TE devices falls significantly short of the Carnot efficiency, rendering them less competitive compared to other sustainable energy technologies and hindering wider adoption.
        In light of this, the pursuit of high-performance TE materials has become a central focus of TE research, given their immense potential for efficient cooling, energy harvesting, and sensing applications. Over the past two decades, the discovery of novel materials and the development of innovative engineering strategies have significantly enhanced the zT values of TE materials. However, despite these advances, the core selection criteria for parent compounds, along with the conventional approaches of doping, alloying, and compositing, have remained largely unchanged for decades. This underscores an urgent need for groundbreaking concepts and new methodologies to drive the development of next-generation TE materials and unlock their full potential. Thermoelectric research is not only a course of materials by discovery but also a seedbed of novel concepts and methodologies. We warmly welcome collaborators and partners who share our passion for pushing the boundaries of thermoelectric performance and exploring new horizons in sustainable energy technologies.

Lattice dynamics of halide perovskites and superionic thermoelectrics












        Materials featuring complex crystal structures, weak interatomic bonds, strong anharmonicity, and glass-like frameworks often exhibit inherently low lattice thermal conductivity. This can be further suppressed through strategies like hierarchical microstructuring, multinary alloying, and the introduction of point defects, dislocations, or interfaces. However, when the phonon mean free path (MFP) is reduced to the scale of interatomic spacing, the lattice thermal conductivity reaches the amorphous limit—the ultimate threshold beyond which lattice periodicity and structural order are completely disrupted. In this context, the innovative concept of phonon-liquid electron-crystal has emerged as a promising pathway for advanced phonon engineering. Superionic thermoelectrics and organic-inorganic hybrid perovskites are prime examples, exhibiting a unique crystal-liquid duality. These materials possess a rigid sublattice with fixed atoms and a dynamic sublattice where delocalized cations rapidly jump or rotate between equilibrium positions, mimicking the behavior of a liquid. This dual nature allows for a crystalline-like response in electronic transport and a liquid-like response in phonon transfer, offering a remarkable opportunity to achieve breakthrough zT values.
       In this context, we aim to uncover the unique lattice dynamics within crystal-liquid hybrid structures that result in ultralow thermal conductivity. To achieve this, we conduct inelastic neutron scattering (INS) measurements on large single crystals, which provide direct insights into phonon dispersion relations and lifetimes. By combining these measurements with first-principles lattice dynamics calculations and molecular dynamics simulations, we will gain a deeper understanding of multi-phonon interactions, phonon softening, electron-phonon coupling, and the influence of superionic cations on thermoelectric properties.