Chemical Pressure-Driven Band Convergence and Discordant Atoms Intensify Phonon Scattering Leading to High Thermoelectric Performance in SnTe.

SnTe is an intriguing alternative to PbTe for midtemperature thermoelectric applications. Despite steady progress, its performance is lagging, in part because of the large energy difference(Δ) between the light (L-band) and heavy (Σ-band) valence bands and higher lattice thermal conductivity (κ). Previous studies have shown that applying pressure can enhance the Seebeck coefficient () and power factor () of SnTe.

Ultrafast Photoinduced Phase Change in SnSe.

Time-resolved multiterahertz (THz) spectroscopy is used to observe an ultrafast, nonthermal electronic phase change in SnSe driven by interband photoexcitation with 1.55 eV pump photons. The transient THz photoconductivity spectrum is found to be Lorentzian-like, indicating charge localization and phase segregation.

Modulation of Vacancy Defects and Texture for High Performance n-Type Bi Te via High Energy Refinement.

The carrier concentration in n-type layered Bi Te -based thermoelectric (TE) material is significantly impacted by the donor-like effect, which would be further intensified by the nonbasal slip during grain refinement of crushing, milling, and deformation, inducing a big challenge to improve its TE performance and mechanical property simultaneously. In this work, high-energy refinement and hot-pressing are used to stabilize the carrier concentration due to the facilitated recovery of cation and anion vacancies. Based on this, combined with SbI doping and hot deformation, the optimized carrier concentration and high texture degree are simultaneously realized.

Dynamic crystallography reveals spontaneous anisotropy in cubic GeTe.

Cubic energy materials such as thermoelectrics or hybrid perovskite materials are often understood to be highly disordered. In GeTe and related IV-VI compounds, this is thought to provide the low thermal conductivities needed for thermoelectric applications. Since conventional crystallography cannot distinguish between static disorder and atomic motions, we develop the energy-resolved variable-shutter pair distribution function technique.

Triple-Wavelength Lasing with a Stabilized β-LaBSiO:Nd Crystal.

Multi-wavelength lasers, especially the triple-wavelength laser around 1060 nm, could be produced by the F → I transition of Nd and present numerous challenges and opportunities in the field of optoelectronics. The Nd-doped high-temperature phase of LaBSiO (β-LBSO) is an ideal crystal to produce triple-wavelength lasers; however, the crystal growth is challenging because of the phase transition from β-LBSO to low-temperature phase (α-LBSO) at 162 °C. This phase transition is successfully suppressed when the doping content of Nd is larger than 6.

Valence Disproportionation of GeS in the PbS Matrix Forms PbGeS Inclusions with Conduction Band Alignment Leading to High n-Type Thermoelectric Performance.

Converting waste heat into useful electricity using solid-state thermoelectrics has a potential for enormous global energy savings. Lead chalcogenides are among the most prominent thermoelectric materials, whose performance decreases with an increase in chalcogen amounts (e.g.

Thermoelectric Performance of the 2D BiSiTe Semiconductor.

BiSiTe, a 2D compound, is a direct band gap semiconductor with an optical band gap of ∼0.25 eV, and is a promising thermoelectric material. Single-phase BiSiTe is prepared by a scalable ball-milling and annealing process, and the highly densified polycrystalline samples are prepared by spark plasma sintering.

Direct visualization of polaron formation in the thermoelectric SnSe.

SnSe is a layered material that currently holds the record for bulk thermoelectric efficiency. The primary determinant of this high efficiency is thought to be the anomalously low thermal conductivity resulting from strong anharmonic coupling within the phonon system. Here we show that the nature of the carrier system in SnSe is also determined by strong coupling to phonons by directly visualizing polaron formation in the material.

Polycrystalline SnSe with a thermoelectric figure of merit greater than the single crystal.

Thermoelectric materials generate electric energy from waste heat, with conversion efficiency governed by the dimensionless figure of merit, ZT. Single-crystal tin selenide (SnSe) was discovered to exhibit a high ZT of roughly 2.2-2.

Defect engineering in thermoelectric materials: what have we learned?

Thermoelectric energy conversion is an all solid-state technology that relies on exceptional semiconductor materials that are generally optimized through sophisticated strategies involving the engineering of defects in their structure. In this review, we summarize the recent advances of defect engineering to improve the thermoelectric (TE) performance and mechanical properties of inorganic materials. First, we introduce the various types of defects categorized by dimensionality, i.

Demonstration of Energy-Resolved γ-Ray Detection at Room Temperature by the CsPbCl Perovskite Semiconductor.

The detection of γ-rays at room temperature with high-energy resolution using semiconductors is one of the most challenging applications. The presence of even the smallest amount of defects is sufficient to kill the signal generated from γ-rays which makes the availability of semiconductors detectors a rarity. Lead halide perovskite semiconductors exhibit unusually high defect tolerance leading to outstanding and unique optoelectronic properties and are poised to strongly impact applications in photoelectric conversion/detection.

Strong Valence Band Convergence to Enhance Thermoelectric Performance in PbSe with Two Chemically Independent Controls.

We present an effective approach to favorably modify the electronic structure of PbSe using Ag doping coupled with SrSe or BaSe alloying. The Ag 4d states make a contribution to in the top of the heavy hole valence band and raise its energy. The Sr and Ba atoms diminish the contribution of Pb 6s states and decrease the energy of the light hole valence band.

High Figure of Merit in Gallium-Doped Nanostructured n-Type PbTe-GeTe with Midgap States.

PbTe-based thermoelectric materials are some of the most promising for converting heat into electricity, but their n-type versions still lag in performance the p-type ones. Here, we introduce midgap states and nanoscale precipitates using Ga-doping and GeTe-alloying to considerably improve the performance of n-type PbTe. The GeTe alloying significantly enlarges the energy band gap of PbTe and subsequent Ga doping introduces special midgap states that lead to an increased density of states (DOS) effective mass and enhanced Seebeck coefficients.

Enhancement of Thermoelectric Performance for n-Type PbS through Synergy of Gap State and Fermi Level Pinning.

We report that Ga-doped and Ga-In-codoped n-type PbS samples show excellent thermoelectric performance in the intermediate temperature range. First-principles electronic structure calculations reveal that Ga doping can cause Fermi level pinning in PbS by introducing a gap state between the conduction and valence bands. Furthermore, Ga-In codoping introduces an extra conduction band.

All-Scale Hierarchically Structured p-Type PbSe Alloys with High Thermoelectric Performance Enabled by Improved Band Degeneracy.

We show an example of hierarchically designing electronic bands of PbSe toward excellent thermoelectric performance. We find that alloying 15 mol % PbTe into PbSe causes a negligible change in the light and heavy valence band energy offsets (Δ E) of PbSe around room temperature; however, with rising temperature it makes Δ E decrease at a significantly higher rate than in PbSe. In other words, the temperature-induced valence band convergence of PbSe is accelerated by alloying with PbTe.

Hierarchical GeP/Carbon Nanocomposite with Dual-Carbon Conductive Network as Promising Anode Material for Sodium-Ion Batteries.

Due to the Earth's scarcity of lithium, replacing lithium with earth-abundant and low-cost sodium for sodium-ion batteries (SIBs) has recently become a promising substitute for lithium-ion batteries. However, the shortage of appropriate anode materials limits the development of SIBs. Here, a dual-carbon conductive network enhanced GeP (GeP/acetylene black/partially reduced graphene oxide sheets (GeP/AB/p-rGO)) composite is successfully prepared by a facile ball milling method.

Scalable Synthesis of Honeycomblike VO/Carbon Nanotube Networks as Enhanced Cathodes for Lithium-Ion Batteries.

A green and scalable route to form a honeycomblike macroporous network by homogeneously weaving VO nanowires and carbon nanotubes (CNTs) was developed. The intertwinement between VO nanowires and CNTs not only integrates nanopores into the macroporous system but also elevates the collection and transfer of charges through the conductive network. The unique combination of VO nanowires and CNTs renders the composite monolith with synergic properties for substantially enhancing electrochemical kinetics of lithiation/delithiation when used as a lithium-ion battery (LIB) cathode.

Homologous Series of 2D Chalcogenides Cs-Ag-Bi-Q (Q = S, Se) with Ion-Exchange Properties.

Four new layered chalcogenides CsAgBiS, CsAgBiSe, CsAgBiS, and CsAgBiSe are described. CsAgBiS and CsAgBiSe are isostructural and have a hexagonal P6/mmc space group; their structures consist of [Ag/Bi]Q (Q = S, Se) quintuple layers intercalated with disordered Cs cations. CsAgBiS also adopts a structure with the hexagonal P6/mmc space group and its structure has an [Ag/Bi]S layer intercalated with a Cs layer.

Co S /MoS Yolk-Shell Spheres for Advanced Li/Na Storage.

Uniform sized Co S /MoS yolk-shell spheres with an average diameter of about 500 nm have been synthesized by a facile route. When evaluated as anodes for lithium-ion and sodium-ion batteries, these Co S /MoS yolk-shell spheres show high specific capacities, excellent rate capabilities, and good cycling stability.

Controllable Preparation of Square Nickel Chalcogenide (NiS and NiSe2) Nanoplates for Superior Li/Na Ion Storage Properties.

A facile and bottom-up approach has been presented to prepare 2D Ni-MOFs based on cyanide-bridged hybrid coordination polymers. After thermally induced sulfurization and selenization processes, Ni-MOFs were successfully converted into NiS and NiSe2 nanoplates with carbon coating due to the decomposition of its organic parts. When evaluated as anodes of Li-ion batteries (LIBs) and Na-ion batteries (NIBs), NiS and NiSe2 nanoplates show high specific capacities, excellent rate capabilities, and stable cycling stability.

[Primary study of corneal exposure ratio measured by Photoshop pixel method].

Objective: To investigate the role of corneal exposure ratio in eyelid aesthetic assessment through the measurement by Photoshop pixel method in beauties and patients with double eyelid blepharoplasty.

Methods: 30 cases of female beauties and 43 cases with double eyelid blepharoplasty(23 cases with suture method and 20 cases with incision method) underwent measurement of corneal exposure ratio by Photoshop pixel method before operation and half a year after operation. The results were analyzed by SPSS 16.

A 3D Chemically Modified Graphene Hydrogel for Fast, Highly Sensitive, and Selective Gas Sensor.

Reduced graphene oxide (RGO) has proved to be a promising candidate in high-performance gas sensing in ambient conditions. However, trace detection of different kinds of gases with simultaneously high sensitivity and selectivity is challenging. Here, a chemiresistor-type sensor based on 3D sulfonated RGO hydrogel (S-RGOH) is reported, which can detect a variety of important gases with high sensitivity, boosted selectivity, fast response, and good reversibility.

Synthesis and characterization of a new mid-infrared transparent compound: acentric Ba5In4Te4S7.

A new noncentrosymmetric (NCS) sulfide, Ba5In4Te4S7, was synthesized by a conventional solid-state reaction in evacuated closed silica tubes. The compound crystallizes in the orthorhombic space group Imm2 (44), with unit cell parameters a = 39.110(3) Å, b = 4.

Bi2Te(IO3)O5Cl: a novel polar iodate oxychloride exhibiting a second-order nonlinear optical response.

The novel iodate oxychloride, Bi2Te(IO3)O5Cl, has been hydrothermally synthesized and structurally characterized. The compound crystallizes in the polar monoclinic space group Cc with a = 22.037(8) Å, b = 5.