Rational Design of 3d Transition-Metal Compounds for Thermoelectric Properties by Using Periodic Trends in Electron-Correlation Modulation.

The electronic structures in solid-state transition-metal compounds can be represented by two parameters: the charge-transfer energy (Δ), which is the energy difference between the p-band of an anion and an upper Hubbard band contributed by transition-metal d-orbitals, and the onsite Coulomb repulsion energy (), which represents the energy difference between lower and upper Hubbard bands composed of split d-orbitals in transition metals. These parameters can facilitate the classification of various types of electronic structures. In this study, the dependences of anion species (N, P, As, O, S, Se, Te, F, Cl, Br, and I) on Δ and of 566 different binary and ternary 3d transition-metal compounds were investigated using ionic-model calculations.

Control of Competing Thermodynamics and Kinetics in Vapor Phase Thin-Film Growth of Nitrides and Borides.

Thin-film  growth is a platform technique that allows the preparation of various undeveloped materials and enables the development of novel energy generation devices. Preferred phase formation, control of crystalline orientation and quality, defect concentration, and stoichiometry in thin films are important for obtaining thin films exhibiting desired physical and chemical properties. In particular, the control of crystalline phase formation by utilizing thin-film technology favors the preparation of undeveloped materials.

Drastic power factor improvement by Te doping of rare earth-free CoSb-skutterudite thin films.

In the present study, we have focused on the elaboration of control of Te-doped CoSb thin films by RF magnetron sputtering which is an attractive technique for industrial development of thermoelectric (TE) thin films. We have successfully synthesized sputtering targets with a reliable approach in order to obtain high-quality films with controlled stoichiometry. TE properties were then probed and revealed a reliable n-type behavior characterized by poor electrical transport properties.

d orbital character of polyhedra in complex solid-state transition-metal compounds.

In transition-metal compounds, the character of the d orbitals often plays an important role in the development and enhancement of novel physical and chemical properties. Density functional theory calculations of the electronic structures of various d0- and d1-complex transition-metal compounds consisting of either face-sharing octahedra, edge-sharing octahedra, or edge-sharing trigonal prismatic layers were performed to investigate the nature of their d orbitals. The dz2 orbital of the transition metal was shown to make a significant contribution to the electronic structure near the Fermi level in nine different complex transition-metal compounds (oxides, nitrides, and sulfides), regardless of the type of polyhedral geometry and connectivity.

Thermoelectric materials and applications for energy harvesting power generation.

Thermoelectrics, in particular solid-state conversion of heat to electricity, is expected to be a key energy harvesting technology to power ubiquitous sensors and wearable devices in the future. A comprehensive review is given on the principles and advances in the development of thermoelectric materials suitable for energy harvesting power generation, ranging from organic and hybrid organic-inorganic to inorganic materials. Examples of design and applications are also presented.

Three-dimensionality of electronic structures and thermoelectric transport in SrZrN₂ and SrHfN₂ layered complex metal nitrides.

Layered materials have several properties that make them suitable as high-performance thermoelectric materials. In this study, we focus on the complex metal nitrides SrZrN2 and SrHfN2, which have an α-NaFeO2 layered crystal structure. To determine their electronic band structure features and potential thermoelectric transport properties, we calculated the electronic band structures and electronic transport coefficients for SrZrN2 and SrHfN2 using density-functional theory and Boltzmann transport theory, respectively.