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Abstract: The study of the doping process of Bi2Te3 by Pb atoms in wide range of lead concentration ((1.0–80.0)×1018 cm−3) revealed two distinct areas of influence of the incorporated Pb atoms on changes in free carrier concentration. While at lower concentration of incorporated Pb (up to 20×1018 Pb atoms cm−3) the ratio of generated holes to one incorporated Pb atom — Δp/c Pb — falls from value of 1.06 down to 0.55, at higher concentration ((20–80)×1018 Pb atoms cm−3) the value stays constant. The observed behaviour of seeming electrical inactivity of the incorporated Pb atoms is explained by a point defect model taking into account the interaction between the entering Pb atoms and native lattice defects of Bi2Te3 crystal structure. [Copyright &y& Elsevier]

Pb-doped Bi 2 Te 3 single crystals with a Pb concentration of c Pb = 0-9.4 × 10 25 m -3 were prepared from the elements Bi, Pb and Te of 99.999% purity by means of the Bridgman method. Samples of these crystals were characterized by measurements of the Hall coefficient R H ( B∥c ), electrical conductivity σ ⊥c and Seebeck coefficient α( c ⊥Δ T ) over the temperature range 90-420 K. It was found that Pb impurities in Bi 2 Te 3 behave as acceptors; some (40%) of the incorporated Pb atoms are electrically inactive. This effect is explained by the model of crystal lattice defects based on the assumption that the Pb atoms interact with native defects in the crystal lattice of undoped Bi 2 Te 3 , that is with antisite defects and vacancies in the Te sublattice. [ABSTRACT FROM AUTHOR]

From IR reflectivity spectra measurement on natural (0001) cleavage planes of Bi2−xSbxSe3 single crystals (space group D53d–R3m), values of plasma resonance frequency ωp were determined. Using the model respecting the existence of light and heavy electrons the dependence of free current carriers concentration on Sb-atom content in Bi2−xSbxSe3 single crystals (for x=0.0 – 0.4) was obtained. There is a maximum in this dependence at lower Sb concentration (x ≅ 0.024). This effect is explained by a model of point defects, where both the concentration of negatively charged native defects in a Bi2Se3 lattice (anti-site defect Bi′Se, “seven-layer lamellae” Bi3Se−4) and the concentration of vacancies in a selenium sublattice (V••Se) decreases with Sb content. On this basis the observed rise of the Hall mobility RHσ in the range from 500 to 1200 cm2/Vs is explained. [Copyright &y& Elsevier]

Detailed transport studies of single crystals of Bi2Se3 were made in the temperature range of 2–300 K, and the data were analyzed in terms of a model consisting of two groups of electrons—a centrosymmetrical lower conduction band and an upper conduction band located away from the Γ-point. Very good agreement with the experimental data is obtained assuming the electrons are scattered on acoustic phonons and ionized impurities. A rather strong influence of the latter mechanism is attributed to a large number of charged selenium vacancies in Bi2Se3. The fitted transport parameters were used to calculate the electronic portion of the thermal conductivity that, in turn, allowed for the determination of the lattice thermal conductivity. The Debye model provides a good approximation to the temperature dependence of the lattice thermal conductivity. [Copyright &y& Elsevier]

Abstract: The Pd5HgSe compound was synthesised by heating of stoichiometric mixture of elements at 400 °C by means of the evacuated silica glass tube technique. Its crystal structure was refined by Rietveld method from powder X-ray diffraction data. Pd5HgSe adopts tetragonal symmetry, space group P4/mmm, unit cell parameters a = 4.0128(2) Å, c = 7.0378(6) Å, V = 113.33(2) Å3, Z = 1. The crystal structure of Pd5HgSe is composed of alternating slabs of the AuCu3-type cuboctahedra [HgPd12] and the PtHg2-type rectangular prisms [SePd8]. The title compound crystallizes in the Pd5TlAs structure type. The electric resistivity as well as the Seebeck coefficient measurements suggests semimetallic behaviour. [Copyright &y& Elsevier]

This work studied the thermal stability, electrical, and thermoelectrical properties of copper(I) selenide, Cu 2 Se synthesized by high-energy milling in a planetary ball mill. The phase composition was investigated by X-ray powder diffraction analysis and scanning electron microscopy. The conversion of the precursors during mechanochemical synthesis and the stability of the product was monitored by thermal analysis. The dependence of electrical properties on the product porosity was observed. For the densification of Cu 2 Se, the method of spark plasma sintering was applied to prepare suitable samples for thermoelectric characterization. High-temperature thermoelectric properties of synthetic Cu 2 Se were compared to its natural analogue-mineral berzelianite in terms of its potential application in energy conversion. Based on the results a relatively high figure-of-merit, ZT parameter (~ 1.15, T = 770 K) was obtained for undoped Cu 2 Se, prepared by rapid mechanochemical reaction (5 min). Cyclic voltammetry measurements of Na/NaClO 4 /Cu 2 Se cell implied that mechanochemically synthesized Cu 2 Se could be used as a promising intercalation electrode for sodium-ion batteries., (© 2024. The Author(s).)

Metal-organic frameworks (MOFs) are attracting attention as potential proton conductors. There are two main advantages of MOFs in this application: the possibility of rational design and tuning of the properties and clear conduction pathways given by their crystalline structure. We hereby present two new MOF structures, ICR-10 and ICR-11, based on tetratopic phosphinate ligands. The structures of both MOFs were determined by 3D electron diffraction. They both crystallize in the P 3̅ space group and contain arrays of parallel linear pores lined with hydrophilic noncoordinated phosphinate groups. This, together with the adsorbed water molecules, facilitates proton transfer via the Grotthuss mechanism, leading to a proton conductivity of up to 4.26 × 10 -4 S cm -1 for ICR-11. The presented study demonstrates the high potential of phosphinate MOFs for the fabrication of proton conductors.

Metal-organic frameworks (MOFs), owing to their unique architecture, attract consistent attention in the design of high-performance Li battery materials. Here, we report a new category of ion-conducting crystalline materials for all-solid-state electrolytes based on an MIL53(Al) framework featuring a superchaotropic metallacarborane (Li + CoD - ) salt and present the first quantitative data on Li + ion sites, local dynamics, chemical exchange, and the formation of charge-transfer pathways. We used multinuclear solid-state nuclear magnetic resonance (ss-NMR) spectroscopy to examine the mechanism of ionic conductivity at atomic resolution and to elucidate order-disorder processes, framework-ion interactions, and framework breathing during the loading of Li + CoD - species and transfer of Li + ions. In this way, the MIL53(Al)@LiCoD framework was found to adopt an open-pore conformation accompanied by a minor fraction of narrow-pore channels. The inserted Li + ions have two states (free and bound), which both exhibit extensive motions. Both types of Li + ions form mutually communicating chains, which are large enough to enable efficient long-range charge transfer and macroscopic conductivity. The superchaotropic anions undergo high-amplitude uniaxial rotation motions supporting the transfer of Li + cations along them, while the fluctuations of MOF aromatic linkers support the penetration of Li + through the channel walls. Our findings provide a detailed atomic-resolution insight into the mechanism of ionic conductivity and thus have significant implications for the design of the next generation of energy-related materials.

This study deals with the preparation and characterization of metallic nanoinclusions on the surface of semiconducting Bi 2 Se 3 that could be used for an enhancement of the efficiency of thermoelectric materials. We used Au forming a 1D alloy through diffusion (point nanoinclusion) and Mo forming thermodynamically stable layered MoSe 2 nanosheets through the reaction with the Bi 2 Se 3 . The Schottky barrier formed by the 1D and 2D nanoinclusions was characterized by means of atomic force microscopy (AFM). We used Kelvin probe force microscopy (KPFM) in ambient atmosphere at the nanoscale and compared the results to those of ultraviolet photoelectron spectroscopy (UPS) in UHV at the macroscale. The existence of the Schottky barrier was demonstrated at +120 meV for the Mo layer and -80 meV for the Au layer reflecting the formation of MoSe 2 and Au/Bi 2 Se 3 alloy, respectively. The results of both methods (KPFM and UPS) were in good agreement. We revealed that long-time exposure (tens of seconds) to the electrical field leads to deep oxidation and the formation of perturbations greater than 1 µm in height, which hinder the I - V measurements.