Properties and structure of (As2Se3)1 − z (SnSe)z − x(GeSe)x and (As2Se3)1 − z (SnSe2)z − x(GeSe2)x glasses

Two valence states of tin atoms in (As₂Se₃)_{1 ? z} (SnSe)_{z ? x}(GeSe)_x and (As₂Se₃)_{1 ? z} (SnSe₂)_{z ? x}(GeSe₂)_x glasses are identified by Mössbauer and photoelectron spectroscopy. It is demonstrated that the presence of doubly charged tin ions in the structural glass network does not give rise to impurity conduction or impurity optical absorption. The inference is made that these glasses can be treated as semiconductor solid solutions.     

Europium(II) in glasses of the Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript>-MnO-Eu<Subscript>2</Subscript>O<Subscript>3</Subscript> system

Triply and doubly charged states of europium are revealed by ¹⁵¹Eu Mössbauer spectroscopy in the structure of glasses of the composition (mol %) 19.5Al₂O₃, 31.5SiO₂, 26.5MnO, and 22.5Eu₂O₃. The isomer shifts in the Mössbauer spectra of Eu³⁺ and Eu²⁺ ions in the structure of glasses differ from the isomer shifts in the spectra of the Eu₂O₃ and EuO compounds. This difference is explained by the fact that the electron density at ¹⁵¹Eu nuclei is affected by the manganese and aluminum atoms, which are not bound directly to the europium atoms. The broadening of the spectra of the Eu²⁺ ions in glasses is caused by the nonuniform isomer shift.     

Structure and physicochemical properties of glasses in the (As2Se3)1 ? z-(SnSe2)z ? x-(Tl2Se)x and (As2Se3)1 ? z-(SnSe)z ? x-(Tl2Se)x systems

A comparative investigation of glasses in the As₂Se₃)_{1 − z} -(SnSe₂) _{z − x} -(Tl₂Se) _x and (As₂Se₃)_{1 − z} -(SnSe) _{z − x} -(Tl₂Se) _x systems has been performed. In both systems, the glass formation regions are shifted toward the As₂Se₃ compound. Only tin(IV) in the structure of glasses in the (As₂Se₃)_{1 − z} -(SnSe) _{z − x} -(Tl₂Se) _x system is identified by M?ssbauer spectroscopy, whereas glasses in the (As₂Se₃)_{1 − z} -(SnSe) _{z − x} -(Tl₂Se) _x system contain both Sn(II) and Sn(IV). The presence of tin in the oxidation state 2+ in the structural network of the glasses does not lead to impurity conduction. The dependences of the density, the microhardness, and the glass transition temperature on the glass composition are explained in the framework of the model according to which the structure of these glasses is built up of structural units corresponding to the As₂Se₃, AsSe, TlAsSe₂, Tl₂Se, SnSe, and SnSe₂ compounds. It is established that, for crystalline alloys in the (As₂Se₃)_{1 − z} -(SnSe) _{z − x} -(Tl₂Se) _x system, there exist two compounds (Tl₂SnSe₃ and Tl₄SnSe₄), which are formed by the peritectic reactions; however, structural units of these compounds are not formed in the structural network of glasses.     

Radiation stability of tin charge states in the (As2Se3)1−z (SnSe) z − x (GeSe) x glasses

This paper reports on the results of investigations into the radiation stability of tin charge states in the (As₂Se₃)_1?z (SnSe) _{z ? x} (GeSe) _x glasses. It is revealed using ¹¹⁹Sn Mössbauer spectroscopy that gamma irradiation of the (As₂Se₃)_1?z (SnSe) _{z ? x} (GeSe) _x glasses leads to partial oxidation of doubly charged tin ions with the formation of the amorphous (finely dispersed) SnO₂ phase blocked by the glass. As a result, the physicochemical properties (density, microhardness, glass transition temperature, activation energy for electrical conduction) of the glasses exposed to gamma irradiation remain virtually unchanged.     

The two-electron exchange between the <Emphasis Type="Italic">U</Emphasis><Superscript>–</Superscript> tin centers in crystal and glass-like chalcogenide semiconductors

The two-electron exchange between neutral and doubly ionized U ^– tin centers in the partially compensated Pb_0.96Sn_0.02Na_0.01Tl_0.01S hole solid solutions in the temperature range of 80–900 K and in the partially compensated Pb_0.965Sn_0.015Na_0.01Tl_0.01Se hole solid solutions in the temperature range of 80–600 K was studied by ^119mm Sn(^119m Sn) Mössbauer spectroscopy. The activation energy of this process for the Pb_0.96Sn_0.02Na_0.01Tl_0.01S solid solutions is comparable with the depth of the tin energy levels in the PbS band gap and amounts to 0.11(2) eV, while in the Pb_0.965Sn_0.015Na_0.01Tl_0.01Se solid solutions it is comparable with the correlation energy of the donor U ^– tin centers in PbSe and amounts to 0.05(1) eV. It is established that the exchange is implemented by the simultaneous transfer of two electrons with the valence band states involved. In the glass-like (As₂Se₃)_0.3(GeSe)_0.6(SnSe)_0.1 alloy containing quadruply charged six-coordinated tin (singly ionized donor center) and doubly charged three-coordinated tin (singly ionized acceptor center), no traces of the electronic exchange between differently charged tin states was observed up to a temperature of 480 K, which is explained by the fact that the doubly charged and quadruply charged tin centers are in different coordination states.     

Wetting,surface tension,and work of adhesion of As<Subscript>2</Subscript>S<Subscript>3</Subscript> and As<Subscript>2</Subscript>Se<Subscript>3</Subscript> glass melts to quartz glass

The contact angles of the quartz glass surface by the As₂S₃ and As₂Se₃ glass melts and surface tension of these glass melts in the temperature range of 325–370°С have been experimentally measured. The polytherms are linear and possess negative slope in the mentioned temperature range. The work of the adhesion of As₂S₃ and As₂Se₃ glass melts to the quartz glass surface has been calculated and compared to the data on the adhesion strength of the As₂S₃–SiO₂ and As₂Se₃–SiO₂ boundaries of the solid phases.     

Physicochemical and optical properties of glasses in the Ga<Subscript>4</Subscript>Ge<Subscript>21</Subscript>Se<Subscript>50</Subscript>-Sb<Subscript>2</Subscript>Se<Subscript>3</Subscript> system

This paper reports on the results of an investigation into the concentration behavior of the glass-forming ability, heat resistance, glass transition temperature, density, refractive index, transparent spectral region, and impurity optical absorption of glasses in the Ga₄Ge₂₁Se₅₀-Sb₂Se₃ system. The data obtained indicate that glasses in the Ga₄Ge₂₁Se₅₀-Sb₂Se₃ system with a high Sb₂Se₃ content are of interest as materials for use in fiber optics.     

Glass formation and electrical conductivity of glasses in the Na<Subscript>2</Subscript>Se-P<Subscript>2</Subscript>Se<Subscript>5</Subscript> system in a wide temperature range

The glass formation region in the Na₂Se-P₂Se₅ system and the temperature-concentration dependences of the electrical conductivity of glasses have been investigated over a wide range of temperatures. The densities and glass transition temperatures T _g of glasses have been determined. A comparison of the electrical conductivity of glasses in the Na₂Se-P₂Se₅ and Na₂O-P₂O₅ systems has demonstrated that the conductivity of selenium-containing glasses (at 25°C) is approximately three orders of magnitude higher than the electrical conductivity of oxide glasses. The assumption has been made that an increase in the electrical conductivity of glasses with selenium is caused by the increase in the degree of dissociation of Na⁺[Se⁻PSe_3/2] polar structural chemical units and the higher mobility of sodium ions in the oxygen-free matrix.     

Effect of secondary phases on thermoelectric properties of Cu2SnSe3

Cu₂SnSe₃ samples with different secondary phases are prepared from compositions of Cu_xSnSe₃ (x=1.8–2.2) and Cu₂Sn_ySe₃ (y=0.8–1.2), and their thermoelectric properties are investigated. For Cu_xSnSe₃ samples, the secondary phase is SnSe₂ for x=1.8 and 1.9 and SnSe for x=2.2, and nearly single-phase Cu₂SnSe₃ is obtained for x=2.0 and 2.1. For Cu₂Sn_ySe₃ samples, the secondary phase is CuSe for y=0.8 and SnSe for x=1.1 and 1.2, and single-phase Cu₂SnSe₃ is produced for y=0.9 and 1.0. The lattice structure of synthesized Cu₂SnSe₃ depends on the x and y values, which is cubic for x≤2.0 or y≤1.0 and monoclinic for x>2.0 or y>1.0. Compared with the single-phase Cu₂SnSe₃ sample (ZT=0.4₂ at 77₃ K), the samples with SnSe₂ secondary phase show a greatly-enhanced ZT of 0.84 at 773 K, which is likely the best result for un-doped Cu₂SnSe₃ up to now. The samples with SnSe secondary phase exhibit poor thermoelectric properties.     

Spectroscopic Studies and Luminescence Spectra of Dy<Subscript>2</Subscript>O<Subscript>3</Subscript> Doped Lead Phosphate Glasses

Dy^3 +-doped lead phosphate glasses were prepared by a melt quenching technique and investigated through Infrared absorption spectra (IR), photoluminescence (PL), and UV-Visible optical absorption measurements (UV-Vis). The luminescence spectra show two intense bands at 483 and 575 nm, which are attributed to ⁴FH_15/2 (blue) and ⁴FH_13/2 (yellow) transitions, respectively. The optical spectra data was used to evaluate the values of indirect allowed transitions. It was found that the optical band gap increases with Dy₂O₃ content. Variation in optical gap energy with the variation in localized state tails, confirms the theories for localized states in the energy gap of amorphous semiconductors. The characteristic infrared absorption bands of these glasses due to the stretching and bending vibrations were identified and analyzed by the increasing of the Dy₂O₃ content. This fact allowed us to identify the specific structural units which appear in these glasses.     

Shielding Behavior of Gamma-Irradiated MoO<Subscript>3</Subscript> or WO<Subscript>3</Subscript>-Doped Lead Phosphate Glasses Assessed by Optical and FT Infrared Absorption Spectral Measurements

Undoped and MoO₃- or WO₃- doped lead phosphate glasses were prepared by the melting-annealing technique. The glasses were characterized through UV-visible and infrared measurements which were repeated after gamma irradiation. Optical spectrum of binary lead phosphate glass shows distinct ultraviolet bands correlated with unavoidable trace iron impurities within the chemicals used for the preparation of the glasses. UV-visible absorption spectra of MoO₃- or WO₃- doped glasses exhibit additional UV-visible bands which are related to the presence of four oxidation states of the two transition metal (molybdenum or tungsten) ions (Mo³⁺, Mo⁴⁺, Mo⁵⁺, Mo⁶⁺, W³⁺, W⁴⁺, W⁵⁺, W⁶⁺). The extra UV band is related to hexavalent (5d⁰) state while the rest of the visible bands are related to (350–440 nm - trivalent state), (450, 550, 650 nm - tetravalent state) while the broad band centered at about 770 nm (pentavalent state). The intensities of the absorption bands are observed to change with the transition metal content and their valencies. Infrared absorption spectra reveal distinct vibrational bands which are assigned to phosphate groups with sharing of Pb-O vibrations within both the range 460–620 cm^-1 and the range 900–1100 cm^-1 revealing a compact network structure. Gamma irradiation causes a minor increase in intensity of one of the UV band due to suggested photo-oxidation of some trace ferrous ions to additional ferric ions but the remaining spectral curve remains unaffected which is obviously related to some shielding effects of heavy atomic weight of PbO. This heavy metal oxide (PbO) is assumed to retard or prohibit the free passage of free electrons or positive holes generated during the irradiation process.     

Electrical conductivity of CuI-AsI<Subscript>3</Subscript>-As<Subscript>2</Subscript>Se<Subscript>3</Subscript> and CuI-SbI<Subscript>3</Subscript>-As<Subscript>2</Subscript>Se<Subscript>3</Subscript> chalcogenide films prepared by chemical deposition

The electrical conductivity of chalcogenide semiconductor films in the CuI-AsI₃-As₂Se₃ and CuI-SbI₃-As₂Se₃ systems, which have been prepared by chemical deposition from mono-n-butylamine, has been studied as a function of the temperature and film composition. It has been established that the electrical conductivity of the CuI-AsI₃-As₂Se₃ and CuI-SbI₃-As₂Se₃ films is predominantly determined by the copper iodide content. It has been demonstrated that the electrical properties of the chalcogenide glasses and the related films are characterized by the same values to within the experimental error, which is explained by the same model of dissolution of vitreous semiconductors in amines with the retention of the electrical properties of chalcogenide glasses after the deposition of films from their solutions.     

Mineralizer effect on the synthesis of two types of one-dimensional chains silver-selenogermanate and selenostannate

Two type of one-dimensional compounds, K₂Ag₂GeSe₄(2) and K₃AgSn₃Se₈(4), were synthesized with thiophenol as a mineralizer, whilst two oligomers, Cs₄Ge₂Se₆ (1) and K₄Sn₃Se₈(3), were obtained in absence of thiophenol. Compounds 1 and 3 contain dimeric [Ge₂Se₆]^4? and trimeric [Sn₃Se₈]^4? anions, respectively. Compound 2 contains isolated GeSe₄ tetrahedra connected by linear-coordinated Ag⁺ ions to form an infinite anionic chains [Ag₂GeSe₄]^2?. The building blocks [Sn₃Se₈]^4? are linked by tetrahedral coordinated Ag⁺ ions to generate infinite chain [AgSn₃Se₈]^3? of 4.     

Laser Desorption Ionization Time‐of‐Flight Mass Spectrometry of Glasses and Amorphous Films from Ge–As–Se System

Laser Desorption Ionization Time‐of‐Flight Mass Spectrometry was exploited for the characterization of Ge–As–Se chalcogenide glasses and corresponding thin films fabricated using pulsed laser deposition. Main achievement of the paper is the determination of laser generated clusters’ stoichiometry. The clusters observed were As_b⁺ (b = 1–3), Se₂^?, binary As_bSe⁺ (b = 1–3), As_bSe_c^? (b = 1–3, c = 1–4), Ge₂Se_c^? (c = 2–3), As₃Se₂⁺, Ge₂As_b^? (b = 2–3), Ge₃As_b^? (b = 1–2), Ge₃Se₄^?, As₅Se_c^? (c = 4–5), GeAsSe₄^?, Ge_aAsSe₅^? (a = 1–4), GeAs₂Se₃^?, GeAs₃Se₂^?, Ge₂As₂Se₂^?, Ge₂AsSe_c^? (c = 6–7), and GeAs₃Se_c^? (c = 5–6) (in positive as well as in negative ion mode). The stoichiometries of identified species are compared with the structural units of the glasses/thin films revealed via Raman scattering spectra analysis. Some species are suggested to be fragments of bulk glass as well as thin films. Described method is useful also for the evaluation of the contamination of chalcogenide glasses or their thin films.     

Electrical conductivity and the nature of charge carriers in glasses of the Tl<Subscript>2</Subscript>O-B<Subscript>2</Subscript>O<Subscript>3</Subscript> system

The concentration dependence of the electrical conductivity of glasses in the Tl₂O-B₂O₃ system is studied. The nature of charge carriers in this system is experimentally investigated for the first time. It is demonstrated using the Hittorf, Tubandt, and Hebb-Liang-Wagner techniques and the Faraday law that neither Tl⁺ ions nor electrons are involved in the electricity transport. The verification of the Faraday law does not reveal the presence of thallium in the amalgam of the cathode or a change in the sample weight after electrolysis, to within the experimental error. This allows one to make the inference that protons can be charge carriers in glasses of the Tl₂O-B₂O₃ system. It is shown using extended X-ray absorption fine structure (EXAFS) spectroscopy that Tl³⁺ ions and thallium Tl⁰ reduced to the metallic state are absent in the structure of the glasses under investigation. This means that thallium in glasses of the Tl₂O-B₂O₃ system occurs only in the form of Tl⁺ ions. The analysis of the IR spectroscopic data leads to only a qualitative conclusion that the water content in the glasses insignificantly increases with an increase in the thallium oxide content. An increase in the electrical conductivity of glasses in the Tl₂O-B₂O₃ system with an increase in the thallium oxide content is explained by the increase in the number of protons formed upon dissociation of H⁺[BO_4/2]^? structural-chemical units, because their concentration increases with increasing Tl₂O content. In the structure of boron oxide, impurity hydrogen enters predominantly into the composition of H⁺[O_2/2BO^?] structural-chemical units, for which the dissociation energy is higher than that for the H⁺[BO_4/2]^? structural-chemical units. The increase in the concentration of H⁺[BO_4/2]^? structural-chemical units is accompanied by the increase in the number of dissociated protons, which are charge carriers in glasses of the Tl₂O-B₂O₃ system.     

A Resumable Fluorescent Probe BHN-Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@SiO<Subscript>2</Subscript> Hybrid Nanostructure for Fe<Superscript>3+</Superscript> and its Application in Bioimaging

A multifunctional fluorescent probe BHN-Fe₃O₄@SiO₂ nanostructure for Fe³⁺ was designed and developed. It has a good selective response to Fe³⁺ with fluorescence quenching and can be recycled using an external magnetic field. With adding EDTA (2.5?×?10^?5 M) to the consequent product Fe³⁺-BHN-Fe₃O₄@SiO₂, Fe³⁺ can be removed from the complex, and its fluorescence probing ability recovers, which means that this constituted on-off type fluorescence probe could be reversed and reused. At the same time, the probe has been successfully applied for quantitatively detecting Fe³⁺ in a linear mode with a low limit of detection 1.25?×?10^?8 M. Furthermore, the BHN-Fe₃O₄@SiO₂ nanostructure probe is successfully used to detect Fe³⁺ in living HeLa cells, which shows its great potential in bioimaging detection.     

Glass Formation and Ionic Conduction Behavior in GeSe2–Ga2Se3–NaI Chalcogenide System

Series of glassy and glass‐ceramic samples in the GeSe₂–Ga₂Se₃–NaI system is prepared by melt‐quenching technique and the glass‐forming region is well‐defined by XRD investigations. Na‐ion conduction behavior is systemically studied by impedance measurements. For the glasses in the series (100?2x)GeSe₂–xGa₂Se₃–xNaI, ionic conductivities increased with increasing x, whereas the attributed activation energy of ion conduction decreases. The enhanced mechanism is discussed by employing Raman spectra. In addition, the effect of the crystal phases NaI and Ga₂Se₃ on the ionic conduction behavior in the (70?x)GeSe₂–xGa₂Se₃–30NaI samples is discussed. Although it shows that the poorly conducting crystallites of NaI and Ga₂Se₃ have a negative effect on the ionic conductivities in this series, the highest ionic conductivity of 1.65 × 10^?6 S/cm is obtained in the 45GeSe₂–25Ga₂Se₃–30NaI glass. Finally, this study also demonstrates a possible way to search appropriate Na‐ion solid electrolytes for all‐solid‐state batteries.     

Crystal structure of Pb<Subscript>6</Subscript>O[(Si<Subscript>6</Subscript>Al<Subscript>2</Subscript>)O<Subscript>20</Subscript>]

The crystal structure of Pb₆O[(Si₆Al₂)O₂₀)] is investigated using X-ray diffraction. The compound has tetragonal symmetry, space group I4/mmm, a = 11.7162(10) Å, c = 8.0435(12) Å, and V = 1104.13(2) ų. The structure is refined to R ₁ = 0.036 for 562 unique reflections with [F ₀] ≥ 4σF. The structure contains two symmetrically independent positions of the Pb²⁺ cations coordinated by five O atoms (Pb²⁺-O^2? = 2.34–2.68 Å). The TO₄ tetrahedra (T = Si, Al) form tubular [(Si₆Al₂)O₂₀] chains extended along the c axis. The O₄ oxygen atom is not bonded to the Si and Al atoms and is octahedrally coordinated by six Pb atoms with the formation of an oxo-centered OPb₆ octahedron. The assumption is made that, in some of lead silicate and aluminosilicate glasses, a number of oxygen atoms are located outside the tetrahedral structure and represent segregation centers of the Pb²⁺ cations due to the formation of oxo-centered complexes.     

Observation of Meyer-Neldel relation for non-isothermal crystallization in Se<Subscript>70</Subscript>Te<Subscript>30</Subscript> and Se<Subscript>70</Subscript>Te<Subscript>28</Subscript>M<Subscript>2</Subscript> (M = Ag,Sb, Zn) glasses

In the present paper, we report the applicability of Meyer-Neldel rule for pre-exponential factor of non-isothermal crystallization in Se₇₀Te₃₀ and Se₇₀Te₂₈M₂ (M = Ag, Sb, Zn) glasses using DSC technique. We have observed strong correlation between pre-exponential factor K ₀ and activation energy of non-isothermal crystallization E _c for the present glasses.