Study on the thermoelectric characteristics of the ternary alkali metal compound XMgSb (X = K, Rb, Cs)

Abstract

We conducted a comprehensive analysis of the mechanical, transport, and thermoelectric characteristics of XMgSb (X = K, Rb, Cs) alkali metal compounds using first-principles calculations, self-consistent phonon theory, compressive sensing technology, and the Boltzmann transport equation. Our results show that the very low lattice thermal conductivity of these materials is mainly attributed to the strong anharmonicity of the alkali metal atoms, and the lattice thermal conductivity is negatively correlated with the mass of X atoms. Furthermore, we consider five scattering mechanisms to accurately calculate transport properties and electron relaxation times. Notably, we observed that the large electronic dispersion band near the valence band maximum (VBM) leads to the high conductivity of these three compounds, with a flat electronic energy band at the Γ-Z point, which generally implies a larger Seebeck coefficient. The coexistence of good electronic band dispersion and flat electronic bands leads to high conductivity and large Seebeck coefficient, resulting in high thermoelectric (TE) power. Low lattice thermal conductivity and high TE power factor jointly determine the development potential of alkali metal compound XMgSb (X = K, Rb, Cs) in the field of thermoelectricity.

Giant Energy Density via Mechanically Tailored Relaxor Ferroelectric Behavior of PZT Thick Film

“…Interestingly, the nanograin‐engineered RFE PZT thick film sustained ultrahigh electric fields of up to 540 MV m −1 (applied voltage of 2160 V), which is equivalent to the typical E DBS of high‐performance polymer‐based dielectrics [ 32 ] and far superior to other ceramic thick films (Figure S13, Supporting Information). [ 10,13,22,33–45 ] Of particular importance is the observation that despite being thick and polycrystalline form, our PZT films exhibited the same E DBS level as that of thin epitaxial as well as domain‐engineered films and outperformed the polycrystalline films with thickness above 0.9 µm. Thus, the nanograin‐engineered thick films meet the standard of practical applications (Table S2, Supporting Information) requiring a high energy level due to their high voltage (over 1000 V) endurance capacity and easy fabrication route.…”

“…The obtained U rec value is many‐fold larger than the highly amorphous AD film (35.2 J cm −3 ), micrograined AD film (9.8 J cm −3 ), and other dielectric ceramic films (thickness > 1.2 µm) reported by other researchers (Figure 3d). [ 10,13,22,33–45 ] In addition, the nanograin‐engineered AD PZT thick film showed a negligible variation (within an error range of 5–7%) in the energy‐storage properties when measured at different frequencies ranging from 10 Hz to 10 kHz (Figure S16, Supporting Information). We observed that the nanograin‐engineered AD thick films (>2.5 µm) exhibited a better energy‐storage performance (reduced E DBS ) than thinner films (Figure S17, Supporting Information).…”

Metal-Free Synthesis of Selanyl-Substituted Chromenones via Selanylation­/Cyclization of Alkynyl Aryl Ketones

“…Recently, sulfonoselenoates have been utilized for C–Se bond formation. 13 In continuation of our studies on C–Se bond formation, 14 we herein describe an efficient procedure for the synthesis of 2-substituted 3-selanyl-chromenones through a cascade selanylation/cyclization of alkynyl aryl ketones with sulfonoselenoates (Scheme 1d ). This transformation is performed under metal-free conditions and does not require an additional oxidant.…”