Understanding the nature of chemical bonding and lattice dynamics together with their influence on phonon-transport is essential to explore design crystalline solids ultralow thermal conductivity for various applications including thermoelectrics. TlInTe2, interlocked rigid weakly bound substructures, exhibits as low ca. 0.5 W/mK near room temperature, owing rattling Tl cations. Large displacements cations along c-axis, driven by electrostatic repulsion between localized electron clouds Te...

Abstract Understanding the origin of intrinsically low thermal conductivity is fundamentally important to development high‐performance thermoelectric materials, which can convert waste‐heat into electricity. Herein, we report an ultralow lattice (ca. 0.4 W m −1 K ) in mixed valent InTe (that is, In + 3+ Te 2 ), exhibits intrinsic bonding asymmetry with coexistent covalent and ionic substructures. The phonon dispersion exhibits, along low‐energy flat branches, weak instabilities associated...

Realization of high thermoelectric performance in n-type semiconductors is imperative need on account the dearth efficient materials compared to p-type counterpart. Moreover, development based Te-free compounds desirable because scarcity Te Earth's crust. Herein, we report intrinsic ultralow thermal conductivity and near room temperature BiSe, a solid, which recently has emerged as weak topological insulator. BiSe possesses layered structure consisting bismuth bilayer (Bi2) sandwiched...

We investigate the microscopic mechanisms of ultralow lattice thermal conductivity (κ_{l}) in Tl_{3}VSe_{4} by combining a first principles density functional theory based framework anharmonic dynamics with Peierls-Boltzmann transport equation for phonons. include contributions three- and four-phonon scattering processes to phonon lifetimes as well temperature dependent renormalization energies arising from an unusually strong quartic anharmonicity Tl_{3}VSe_{4}. In contrast recent report...

Chemical bonding present in crystalline solids has a significant impact on how heat moves through lattice, and with the right chemical tuning, one can achieve extremely low thermal conductivity. The desire for intrinsically lattice conductivity (κlat) gained widespread attention thermoelectrics, refractories, nowadays photovoltaics optoelectronics. Here we have synthesized high-quality ingot of cubic metal halide CuBiI4 explored its transport properties. It exhibits an ultralow κlat...

Abstract Achieving glass‐like ultra‐low thermal conductivity in crystalline solids with high electrical conductivity, a crucial requirement for high‐performance thermoelectrics , continues to be formidable challenge. A careful balance between and transport is essential optimizing the thermoelectric performance. Despite this inherent trade‐off, experimental realization of an ideal material phonon‐glass electron‐crystal (PGEC) nature has rarely been achieved. Here, PGEC‐like AgSbTe 2...

Recently, metal sulfides have begun to receive attention as potential cost-effective materials for thermoelectric applications beyond optoelectronic and photovoltaic devices. Herein, based on a comparative analysis of the structural transport properties 2D PbSnS2 1D PbSnS3, we demonstrate that intrinsic effects govern low lattice thermal conductivity (κL) these originate from combination dimensionality their crystal structures with stereochemical activity lone-pair electrons cations. The...

Fundamental understanding of the correlation between chemical bonding and lattice dynamics in intrinsically low thermal conductive crystalline solids is important to thermoelectrics, barrier coating, more recently photovoltaics. Two-dimensional (2D) layered halide perovskites have attracted widespread attention optoelectronics solar cells. Here, we discover ultralow conductivity (κL) single crystal all-inorganic Ruddlesden-Popper (RP) perovskite, Cs2PbI2Cl2, synthesized by Bridgman method....

Thermal transport phenomena are ubiquitous and play a critical role in the performance of various microelectronic energy-conversion devices. Binary rocksalt zinc blende compounds, despite their rather simple crystal structures, exhibit an extraordinary range lattice thermal conductivity (κL) spanning over 3 orders magnitude. A comprehensive understanding underlying heat transfer mechanism through development microscopic theories is therefore fundamental importance, yet it remains elusive...

The nontrivial electronic topology of a topological insulator is thus far known to display signatures in robust metallic state at the surface. Here, we establish vibrational anomalies Raman spectra bulk that signify changes topology: an ${E}_{g}^{2}$ phonon softens unusually and its linewidth exhibits asymmetric peak pressure induced transition (ETT) ${\mathrm{Sb}}_{2}{\mathrm{Se}}_{3}$ crystal. Our first-principles calculations confirm from band insulating with reversal parity bands passing...

Synergistic effect of bonding inhomogeneity and local off-centering within global cubic structure results in ultralow thermal conductivity n-type AgPbBiSe₃.

Abstract Semiconductors with very low lattice thermal conductivities are highly desired for applications relevant to energy conversion and management, such as thermoelectrics barrier coatings. Although the crystal structure chemical bonding known play vital roles in shaping heat transfer behavior, material design approaches of lowering conductivity using principles uncommon. In this work, an effective strategy weakening interatomic interactions therefore suppressing based on is presented a...

As the periodic atomic arrangement of a crystal is made to disorder or glassy-amorphous system by destroying long-range order, lattice thermal conductivity, κL, decreases, and its fundamental characteristics changes. The realization ultralow unusual glass-like κL in crystalline material challenging but crucial many applications like thermoelectrics barrier coatings. Herein, we demonstrate an (~0.20 W/m·K at room temperature) temperature dependence (2-400 K) single layered halide perovskite,...

The structural transformation generally occurs from lower symmetric to higher structure on heating. However, the formation of locally broken asymmetric phases upon warming has been evidenced in PbQ (Q = S, Se, Te), a rare phenomenon called emphanisis, which significant effect their thermal transport and thermoelectric properties. (SnSe)0.5(AgSbSe2)0.5 crystallizes rock-salt cubic average structure, with three cations occupying same Wycoff site (4a) Se anion position (Wycoff site, 4b). Using...

Abstract The development of efficient thermal energy management devices such as thermoelectrics and barrier coatings often relies on compounds having low lattice conductivity ( κ l ). Here, we present the computational discovery a large family 628 thermodynamically stable quaternary chalcogenides, AMM′Q 3 (A = alkali/alkaline earth/post-transition metals; M/M′ transition metals, lanthanides; Q chalcogens) using high-throughput density functional theory (DFT) calculations. We validate...

Fundamental understanding of the relationship between chemical bonding, lattice dynamics, and thermal transport is not only crucial for thermoelectrics but also essential in photovoltaics optoelectronics. This leads to a widespread search low thermally conductive crystalline metal halide perovskites with improved electrical stability. Pb-free all-inorganic Sn-based are particularly compelling because their degenerate hole doping capability, which generally results p-type conduction. Herein,...

Abstract Thermal conductivity, which measures the ease at heat passes through a crystalline solid, is controlled by nature of chemical bonding and periodicity in solid. This necessitates an in‐depth understanding crystal structure to tailor materials with notable lattice thermal conductivity ( κ L ). Herein, its influence on transport properties (2–523 K) all‐inorganic halide perovskite Cs 3 Bi 2 I 9 are studied. The exhibits ultralow value ≈0.20 W m −1 K 30–523 temperature range....

Small band gap topological insulators and Weyl semimetals show excellent TE properties. We identify two mechanisms (i) asymmetry in the electronic density of states caused by inversion at an transition (ii) convergence as key to good behavior these materials.

A challenge in thermoelectrics is to achieve intrinsically low thermal conductivity crystalline solids while maintaining a high carrier mobility (μ). Topological quantum materials, such as the topological insulator (TI) or (TCI) can exhibit μ. Weak insulators (WTI) are of interest because their layered hetero-structural nature which has lattice (κlat ). BiTe, unique member (Bi2 )m Te3 )n homologous series (m:n=1:2), both states, TCI and WTI, distinct from conventional strong TI, Bi2 (where...

As one of the major areas interest in catalysis revolves around 2D materials based on molybdenum sulfide, we have examined catalytic properties bismuth selenides and tellurides, which are among first chalcogenides to be proven as topological insulators (TIs). We find significant photochemical H2 evolution activity with these TIs catalysts. increases drastically nanosheets Bi2 Te3 compared single crystals. First-principles calculations show that due topology, surface states participate...

Defect chemistry is critical to designing high performance thermoelectric materials. In SnTe, the naturally large density of cation vacancies results in excessive hole doping and frustrates ability control properties. Yet, recent work also associates with suppressed sound velocities low lattice thermal conductivity, underscoring need understand interplay between alloying, vacancies, transport properties SnTe. Here, we report solid solutions SnTe NaSbTe2 NaBiTe2 (NaSnmSbTem+2 NaSnmBiTem+2,...

SnS2, an earth-abundant and ecofriendly material, is limited as a thermoelectric material because of the high lattice thermal conductivity κL low carrier mobility μ. By introducing weak-bonding elements Ba or Sr into SnS2 framework, we discovered two SnS2-based materials BaSnS3 SrSnS3 with calculated values 0.15 0.17 W m–1 K–1, respectively, along a-axis. The group velocity anharmonicity originating from weakened distorted Sn–S bonding network are found in both systems. Moreover, vibrations...

Abstract We design an advanced machine-learning (ML) model based on crystal graph convolutional neural network that is insensitive to volumes (i.e., scale) of the input structures discover novel quaternary chalcogenides, AMM′Q 3 (A/M/M ' = alkali, alkaline earth, post-transition metals, lanthanides, and Q chalcogens). These compounds are shown possess ultralow lattice thermal conductivity ( κ l ), a desired requirement for thermal-barrier coatings thermoelectrics. Upon screening...

We propose a first-principles model of minimum lattice thermal conductivity ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:msubsup> <mml:mi>κ</mml:mi> <mml:mrow> <mml:mi mathvariant="normal">L</mml:mi> </mml:mrow> mathvariant="normal">min</mml:mi> </mml:msubsup> </mml:math> ) based on unified theoretical treatment transport in crystals and glasses. apply this to thousands inorganic compounds find universal behavior the high-temperature...

Abstract Understanding the origin of intrinsically low thermal conductivity is fundamentally important to development high‐performance thermoelectric materials, which can convert waste‐heat into electricity. Herein, we report an ultralow lattice (ca. 0.4 W m −1 K ) in mixed valent InTe (that is, In + 3+ Te 2 ), exhibits intrinsic bonding asymmetry with coexistent covalent and ionic substructures. The phonon dispersion exhibits, along low‐energy flat branches, weak instabilities associated...