Operando Observation of Electrically Triggered Phase Transition in Thin CuS Crystal.

CuS has been identified as a functional material of memristors with multilevel resistance switching. However, as the migration of Cu ions under the electric field is tangled with defect evolution and phase transition, the electroresistance mechanism of CuS remains largely unclear. Here, the electrically triggered phase transition was studied by transmission electron microscopy.

Roadmap for Power Generation of Industrial Hot Extruded BiTe-Based Thermoelectric Device in Real-World Heat Sources.

Recovering waste heat through thermoelectric (TE) technology is critical for enhancing energy efficiency. However, commercial devices often require n- and p-type thermoelectric units to have similar cross-sectional areas and conductivities, complicating optimization of their figure of merit (). Moreover, real-world heat sources are not constant temperature sources, and only heat flux can be measured.

In Situ STEM Observation of Phase Transition Triggered by Mo Migration in MoTe.

The heterostructure of transition metal dichalcogenides (TMDs), such as one-dimensional (1D) nanowires embedded in two-dimensional (2D) nanosheets, has drawn much research attention due to its unique electronic, spintronic, magnetic, and catalytic properties. The general approach for preparing such a heterostructure is through electron beam lithography or annealing on the 2D template, triggering direct formation of the 1D component within the 2D matrix. However, the thermodynamic mechanism behind the transition from 2D to 1D is still not well clarified.

Rational Design of Cu Vacancies and Antisite Defects for Boosting the Thermoelectric Properties of CuGaTe-Based Compounds.

CuGaTe-based compounds show great promise in the application for high-temperature thermoelectric power generation; however, its wide bandgap feature poses a great challenge for enhancing thermoelectric performance via structural defects modulation and doping the system. Herein, it is discovered that the presence of Ga antisite defects in the CuGaTe compound promotes the formation of Cu vacancies, and vice versa, which tends to form the charge-neutral structure defects combination with one Ga antisite defect and two Cu vacancies. The accumulation of Cu vacancies in the structure of the (CuTe)(GaTe) compounds evolves into twins and stacking faults.

High Ductility and Excellent Thermoelectric Performance in Te-Stabilized Cubic AgTeS Solid Solutions.

The stabilization at low temperatures of the AgS cubic phase could afford the design of high-performance thermoelectric materials with excellent mechanical behavior, enabling them to withstand prolonged vibrations and thermal stress. In this work, we show that the AgTeS solid solutions, with Te content within the optimal range 0.20 ≤ ≤ 0.

Nature of Thermal Hysteresis of Thermoelectric Properties in AgTeS Compounds.

AgTeS usually undergo various phase structures upon heating or cooling processes; however, the correlation between the heat treatment, the phase structure, and the physical properties is still a controversy. Herein, three different phases are realized for AgTeS (0.35 ≤ ≤ 0.

Balanced High Thermoelectric Performance in n-Type and p-Type CuAgSe Realized through Vacancy Manipulation.

As a liquid-like material, CuAgSe has high carrier mobility and ultralow lattice thermal conductivity. It undergoes an n-p conduction-type transition during β- to α-phase transition with increasing temperature. Moreover, optimization of the thermoelectric performance of CuAgSe is rather difficult, owing to the two-carrier conduction in this material.

Vacancy Suppression Induced Synergetic Optimization of Thermoelectric Performance in Sb-Doped GeTe Evidenced by Positron Annihilation Spectroscopy.

Synergetic optimization of the electrical and thermal transport performance of GeTe has been achieved through Sb doping in this work, resulting in a high thermoelectric figure of merit of 2.2 at 723 K. Positron annihilation measurements provided clear evidence that Sb doping in GeTe can effectively suppress the Ge vacancies, and the decrease of vacancy concentration coincides well with the change of hole carrier concentration after Sb doping.

Excellent Stability of Ga-Doped Garnet Electrolyte against Li Metal Anode Eliminating LiGaO Precipitates for Advanced All-Solid-State Batteries.

Ga-doped garnet-type LiLaZrO (Ga-LLZO) ceramics have long been recognized as ideal electrolyte candidates for all-solid-state lithium batteries (ASSLBs). However, in this study, it is shown that Ga-LLZO easily and promptly cracks in contact with molten lithium during the ASSLB assembly. This can be mainly ascribed to two aspects: (i) lithium captures O atoms and reduces Ga ions of the Ga-LLZO matrix, leading to a band-gap closure from >5 to <2 eV and a structural collapse from cubic to tetrahedral; and (ii) the -formed LiGaO impurity phase has severe side reactions with lithium, resulting in huge stress release along the grain boundaries.

High-Performance Thermoelectric α-Ag Ga Te Compounds with Ultralow Lattice Thermal Conductivity Originating from Ag Te Motifs.

We have determined the complex atomic structure of high-temperature α-Ag GaTe phase with a hexagonal lattice (P6 mc space group, a=b=8.2766 Å, c=13.4349 Å).

2D Homologous Series SrFMBiS (M = Pb, AgBi; = 0, 1) and Commensurately Modulated SrFBiS.

We report three new mixed-anion two-dimensional (2D) compounds: SrFPbBiS, SrFAgBiS, and SrFBiS. Their structures as well as the parent compound SrFBiS were refined using single-crystal X-ray diffraction data, with the sequence of SrFBiS, SrFPbBiS, and SrFAgBiS defining the new homologous series SrFMBiS (M = Pb, AgBi; = 0, 1). SrFBiS has a different structure, which is modulated with a vector of 1/3* and was refined in superspace group 2/(0β0)00 as well as in the 1 × 3 × 1 superstructure with space group 2/ (with similar results).

Electrically Tunable Antiferroelectric to Paraelectric Switching in a Semiconductor.

The monoclinic α-CuSe phase is the first multipolar antiferroelectric semiconductor identified recently by electron microscopy. As a semiconductor, although there are no delocalized electrons to form a static macroscopic polarization, a spontaneous and localized antiferroelectric polarization was found along multiple directions. In conventional ferroelectrics, the polarity can be switched by an applied electric field, and a ferroelectric to paraelectric transition can be modulated by temperature.

Doping Achieves High Thermoelectric Performance in SnS: A First-Principles Study.

Among the thermoelectrics discovered in the past few decades, SnS stands out as a promising candidate for its inexpensive, earth-abundant, and environment-friendly merits. However, with emerging research on optimizing the thermoelectric performance of SnS, there are not many theoretical studies giving explicit analysis about the underlying mechanism of charge and heat transport in the system. In this work, we find an abnormal optical-phonon-dominated κ in SnS with heat-carrying optical phonons showing higher group velocity than acoustic phonons.

Enhanced Thermoelectric Properties of CuSnSe-Based Materials with AgSe Addition.

In this work, (Ag, In)-co-doped CuSnSe-based compounds are prepared using a self-propagating high-temperature synthesis process. AgSe and as-synthesized (Ag, In)-co-doped CuSnSe-based powders are mixed in a proportion according to the formula of CuAgSnInSe/ AgSe ( = 0, 3, 4, and 5%), which is followed by a subsequent plasma-activated sintering (PAS) to obtain consolidated composite bulks. A sandwich experiment is designed to reveal the evolution of the microstructure and phase composition of the composite samples during the PAS process.

Enhancing Thermoelectric Performance of AgSbTe-Based Compounds Microstructure Modulation Combining with Entropy Engineering.

Modulation of the microstructure and configurational entropy tuning are the core stratagem for improving thermoelectric performance. However, the correlation of evolution among the preparation methods, chemical composition, structural defects, configurational entropy, and thermoelectric properties is still unclear. Herein, two series of AgSbTe-based compounds were synthesized by an equilibrium melting-slow-cooling method and a nonequilibrium melting-quenching-spark plasma sintering (SPS) method, respectively.

Electroresistance in multipolar antiferroelectric CuSe semiconductor.

Electric field-induced changes in the electrical resistance of a material are considered essential and enabling processes for future efficient large-scale computations. However, the underlying physical mechanisms of electroresistance are currently remain largely unknown. Herein, an electrically reversible resistance change has been observed in the thermoelectric α-CuSe.

Removing the Oxygen-Induced Donor-like Effect for High Thermoelectric Performance in n-Type BiTe-Based Compounds.

Bismuth telluride-based alloys are the best performing thermoelectric materials near room temperature. Grain size refinement and nanostructuring are the core stratagems for improving thermoelectric and mechanical properties. However, the donor-like effect induced by grain size refinement strongly restricts the thermoelectric properties especially in the vicinity of room temperature.

Enhancing the Thermoelectric and Mechanical Properties of BiSbTe Modulated by the Texture and Dense Dislocation Networks.

BiTe-based materials are dominating thermoelectrics for almost all of the room-temperature applications. To meet the future demands, both their thermoelectric (TE) and mechanical properties need to be further improved, which are the requisite for efficient TE modules applied in areas such as reliable micro-cooling. The conventional zone melting (ZM) and powder metallurgy (PM) methods fall short in preparing BiTe-based alloys, which have both a highly textured structure for high TE properties and a fine-grained microstructure for high mechanical properties.

Synergistically Enhanced Thermoelectric Performance of CuSnSe-Based Composites Ag Doping Balance.

As an ecofriendly and low-cost thermoelectric material, CuSnSe has recently drawn much attention. In this work, the thermoelectric properties of CuSnSe-based materials have been synergistically optimized. Ag doping at the Cu site enables strong phonon scattering via large strain field fluctuations and increases the effective mass of carriers through band engineering, which results in a reduced lattice thermal conductivity and enhanced Seebeck coefficient.

Fast ion transport for synthesis and stabilization of β-ZnSb.

Mobile ion-enabled phenomena make β-ZnSb a promising material in terms of the re-entry phase instability behavior, mixed electronic ionic conduction, and thermoelectric performance. Here, we utilize the fast Zn migration under a sawtooth waveform electric field and a dynamical growth of 3-dimensional ionic conduction network to achieve ultra-fast synthesis of β-ZnSb. Moreover, the interplay between the mobile ions, electric field, and temperature field gives rise to exquisite core-shell crystalline-amorphous microstructures that self-adaptively stabilize β-ZnSb.

Ultralow Thermal Conductivity, Multiband Electronic Structure and High Thermoelectric Figure of Merit in TlCuSe.

The entanglement of lattice thermal conductivity, electrical conductivity, and Seebeck coefficient complicates the process of optimizing thermoelectric performance in most thermoelectric materials. Semiconductors with ultralow lattice thermal conductivities and high power factors at the same time are scarce but fundamentally interesting and practically important for energy conversion. Herein, an intrinsic p-type semiconductor TlCuSe that has an intrinsically ultralow thermal conductivity (0.

Mechanical Properties and Thermal Stability of the High-Thermoelectric-Performance CuSe Compound.

The CuSe compound possesses extraordinary thermoelectric performance at high temperatures and shows great potential for the application of waste heat recycling. However, a thermoelectric device usually undergoes mechanical vibration, mechanical and/or thermal cycling, and thermal shock in service. Therefore, mechanical properties are of equal importance as thermoelectric performance.

Zn-Induced Defect Complexity for the High Thermoelectric Performance of n-Type PbTe Compounds.

Although defect engineering is the core strategy to improve thermoelectric properties, there are limited methods to effectively modulate the designed defects. Herein, we demonstrate that a high value of 1.36 at 775 K and a high average value of 0.