We proposed a new concept of increasing the plasticity of chalcogenide glasses while maintaining a high glass transition temperature. The main idea of this concept lies in the formation of Ag–Ag ...metallophilic interactions when silver chalcogenide is introduced into the glass composition. This suggestion was confirmed by the experimental study of glasses based on the Ag2Se–Sb2Se3–GeSe2 system. It was observed that the introduction of 40 mole percent of Ag2Se into the glass composition leads to the increase of its plasticity by 3.5 times, whereas the glass transition temperature of such glass remains higher than 200 °C. The most typical application area of these materials is infrared (IR) optics. In our case, the addition of silver not only improves the mechanical properties of a glass but also allows one to keep the position of the fundamental absorption edge in the near-IR region (900 nm), which is quite suitable for the aforementioned applications.
Using the laser ablation method, films comprised of alternating layers of AgI and (GeSe2)30(Sb2Se3)30(AgI)40 glass were obtained. Individual layer thickness amounts to 10÷15nm, and the total number ...of layers is about 100. X-ray diffraction (XRD) and film conductivity measurements were carried out during several cycles of heating up to 200°C and cooling to room temperature. It was established that after three cycles of thermal processing specific lateral conductivity of the film is equal to 0.3Scm−1 and conductivity activation energy is equal to 0.07eV at room temperature. Attempts to explain such a high conductivity value based on XRD results did not yield satisfactory results. However, our first-principle calculations within the density functional theory (DFT) showed that in the free layer composed of four AgI planes a rearrangement occurs, resulting in formation of the stable structure of two silver planes on the inside and two iodine planes on the outside (I–Ag–Ag–I). Rearrangement of similar stack of eight or twelve atomic planes results in formation of two or three I–Ag–Ag–I layers loosely bound to each other, accordingly. This suggests that increase in specific conductivity growth of multilayer film as a consequence of cyclic heating and cooling may be connected with AgI stratification on its boundary with chalcogenide glass and following stabilization of layered phases mentioned above. The existence of an empty space between the layers that is constrained by iodine ion planes should facilitate silver ion diffusion along the layers.
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•The prepared nanolayered solid electrolyte demonstrates unique superionic properties.•The layered AgI polymorphs were established using the first principles calculations.•A new conductivity mechanism of AgI has been supposed.
Copper(II) complexes are extremely labile with typical ligand exchange rate constants on the order of 106–109 M–1 s–1. As a result, it is often difficult to identify the actual formation mechanism ...of these complexes. In this work, using UV–vis transient absorption when probing in a broad time range (20 ps to 8 μs) in conjunction with DFT/TDDFT calculations, we studied the dynamics and underlying reaction mechanisms of the formation of extremely labile copper(II) CuCl4 2– chloro complexes from copper(II) CuCl3 – trichloro complexes and chloride ions. These two species, produced via photochemical dissociation of CuCl4 2– upon 420 nm excitation into the ligand-to-metal-charge-transfer electronic state, are found to recombine into parent complexes with bimolecular rate constants of (9.0 ± 0.1) × 107 and (5.3 ± 0.4) × 108 M–1 s–1 in acetonitrile and dichloromethane, respectively. In dichloromethane, recombination occurs via a simple one-step addition. In acetonitrile, where CuCl3− reacts with the solvent to form a CuCl3CH3CN− complex in less than 20 ps, recombination takes place via ligand exchange described by the associative interchange mechanism that involves a CuCl4CH3CN2– intermediate. In both solvents, the recombination reaction is potential energy controlled.
•Amorphous films of Ag2Se were prepared using laser ablation.•The oriented crystalline structure was formed with further temperature cycling.•High-temperature modification of Ag2Se was stabilized in ...the films at room temperature.•Stabilized Ag2Se high-temperature modification is subjected to a mechanical stress.
Amorphous films of Ag2Se were prepared by laser ablation. After being heated up to 270 °C, the films form oriented crystalline structure of orthorhombic β-modification upon further cooling at temperatures of 110 – 90 °С. The films undergo reversible β↔α phase transitions during the following temperature cycling, while the oriented crystalline structure stays the same. X-ray analysis showed no impurities reflections, excluding the one with very low intensity attributed to an elemental silver. The silver nanocrystals apparently form due to the selenium evaporation from the film surface during heating. The temperature dependence of the film's conductivity coincides with the one for bulk stoichiometric Ag2Se samples.
It was shown that a considerable amount of α-Ag2Se is preserved in the film at room temperature even at low cooling rate. This phase is subjected to a significant mechanical stress caused by a density difference between α and β modifications. This circumstance points to the possibility of stabilization of high-temperature superionic modification of Ag2Se at room temperature in a nanolayered structure, in which some alternating layers create a similar stress on the Ag2Se layers.
Superionic nanolayered structure based on amorphous Ag2Se Tveryanovich, Yury S.; Razumtcev, Aleksandr A.; Fazletdinov, Timur R. ...
The Journal of physics and chemistry of solids,
January 2021, 2021-01-00, Letnik:
148
Journal Article
Recenzirano
A regular nanocomposite, consisting of 62 alternating Ag2Se and chalcogenide glass nanolayers of identical thickness, was fabricated by Pulsed Laser Deposition. The total thickness of the ...nanostructure is 700 nm. The Ag2Se layers in the nanostructure are amorphous in a wide temperature range, unlike the individual layers of this compound. A method for determining values of ionic and electronic conductivity components is proposed. It was found that the obtained nanostructure possesses high ionic conductivity at room temperature (≈10 Ω−1cm−1), which is comparable to the conductivity of superionic electrolytes.
Synthesized nanostructures may find applications as solid electrolytes, as well as in the production of flexible electronics in combination with silver sulfide Ag2S.
•Amorphous nanostructures made of alternating layers of Ag2Se and chalcogenide glass were prepared by laser ablation.•The method for determining values of ionic and electronic conductivity components was proposed.•Obtained nanostructures possess ionic conductivity of 10 (Ohm*cm)−1 at room temperature.•Nanolayers of amorphous Ag2Se were studied for the first time.
•Relaxation pathways of the LMCT-excited Cu(II) Cl-complexes in CH3CN were revealed.•Combination of the steady-state photolysis and ultrafast spectroscopy was used.•Major part of the LMCT-excited ...complexes relaxes to ground state parent complex.•Minor fraction of the LMCT-excited complexes dissociates into photoproducts.•CuIICln2−n photodissociate into CuIICln−13−n+Cl− and CuICln−12−n+Cl.
Photochemistry of Cu(MeCN)3Cl+, Cu(MeCN)Cl3−, and CuCl42− copper(II) chlorocomplexes in acetonitrile solution is studied by means of the combination of the steady-state photolysis and ultrafast transient absorption methods. The main relaxation pathways of the initially excited ligand-to-metal charge transfer states are internal conversion to the ground state, ionic dissociation without (photo)reduction of copper(II), and radical dissociation with (photo)reduction of copper(II). The copper(II)-to-copper(I) photoreduction quantum yields obtained from steady-state photolysis correlate with ultrafast spectroscopy data. The presence of oxygen does not affect the photoreduction quantum yields, which do not exceed 7% for the complexes studied and decrease in the series: Cu(MeCN)3Cl+>Cu(MeCN)Cl3−>CuCl42−.
Laser-induced copper deposition from solution is accompanied by the evolution of two types of gas objects that differ considerably in the geometric sizes of bubbles, optical properties and effects on ...the copper deposition process.
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