Two-electron tin centers formed in chalcogenide glasses as a result of nuclear transformations

The ^119mSn impurity atoms formed as a result of the radioactive transformation of the ^119mmSn parent atoms in the structure of glasses in the As-S and As-Se systems and the As₂Te₃ glass are involved in the glass composition in the form of Sn⁴⁺ ions. The ^119mSn impurity atoms formed after the radioactive decay of the ¹¹⁹Sb atoms in the structure of glasses in the As-S and As-Se systems are located in the arsenic sites and play the role of two-electron centers with a negative correlation energy. For the As₂Te₃ glass, the ^119mSn atoms formed in a similar manner are electrically inactive. The larger part of the ^119mSn daughter atoms, which are formed after the radioactive decay of the ^119mTe parent atoms in glasses of the As-S and As-Se systems and in the As₂Te₃ glass, are located in the chalcogen sites and are electrically inactive. The significant recoil energy of the daughter atoms in the case of decay of the ^119mTe atoms leads to the appearance of displaced ^119mSn atoms.     

Structural-chemical features of crystallizing glasses of the Se-Sn and As2Se3-Sn systems

The nearest environment of tin atoms and the regions of the existence of the Sn(IV) and Sn(II) states in hardened glasses of the As₂Se₃-Sn system have been determined based on the study of Mössbauer spectra on ¹¹⁹Sn nuclei and long-wavelength IR spectra, thermodynamic calculations, analysis, and the generalization of the data from measuring microhardness, density, electric conductivity parameters and other data. The probable structural-chemical models of SeSn _x (x < 0.01) and AsSe_1.5Sn _x (x < 0.3) glasses inclined to crystallization have been proposed.     

Mechanochemical stability of Ge1 − x − y Sn y Te x glasses

The mechanochemical stability of glasses in the Ge_{1 ? x ? y} Sn _y Te _x system is investigated. It is found that tin in Ge_{1 ? x ? y} Sn _y Te _x vitreous alloys forms a system of sp ³ chemical bonds and that Ge_{1 ? x} Sn _x Te solid solutions are formed in crystalline alloys. The dispersion of glasses at room temperature in air is accompanied by the precipitation of the SnO₂ amorphous phase.     

Charge state of tin atoms substituting for tellurium atoms in the structural network of the Ge1 ? x ? y Sn y Te x glasses

The Ge_{1 − x − y} Sn _y Te _x vitreous alloys are studied using ¹¹⁹Sn M?ssbauer spectroscopy. It is found that the quadruply charged tin ions substituting for germanium in the vitreous alloys under investigation forms an sp ³ system of chemical bonds, whereas the doubly charged tin ions substituting for tellurium exhibit a metallic character of bonds with tellurium atoms in its own local environment. Original Russian Text ? E.S. Khuzhakulov, 2007, published in Fizika i Khimiya Stekla.     

High Na‐ion conducting Na1+x[SnxGe2−x(PO4)3] glass‐ceramic electrolytes: Structural and electrochemical impedance studies

Na‐ion conducting Na_1+x[Sn_xGe_2?x(PO₄)₃] (x = 0, 0.25, 0.5, and 0.75 mol%) glass samples with NASICON‐type phase were synthesized by the melt quenching method and glass‐ceramics were formed by heat treating the precursor glasses at their crystallization temperatures. XRD traces exhibit formation of most stable crystalline phase NaGe₂(PO₄)₃ (ICSD‐164019) with trigonal structure. Structural illustration of sodium germanium phosphate [NaGe₂(PO₄)₃] displays that each germanium is surrounded by 6 oxygen atom showing octahedral symmetry (GeO₆) and phosphorous with 4 oxygen atoms showing tetrahedral symmetry (PO₄). The highest bulk Na⁺ ion conductivities and lowest activation energy for conduction were achieved to be 8.39 × 10^?05 S/cm and 0.52 eV for the optimum substitution levels (x = 0.5 mol%, Na_1.5[Sn_0.5Ge_1.5(PO₄)₃]) of tetrahedral Ge⁴⁺ ions by Sn⁴⁺ on Na–Ge–P network. CV studies of the best conducting Na_1.5[Sn_0.5Ge_1.5(PO₄)₃] glass‐ceramic electrolyte possesses a wide electrochemical window of 6 V. The structural and EIS studies of these glass‐ceramic electrolyte samples were monitored in light of the substitution of Ge by its larger homologue Sn.     

Local structure of semiconductor glasses in the germanium-sulfur and germanium-selenium systems

¹²⁹Te(¹²⁹I) and ¹¹⁹Sn Mössbauer investigations have revealed that the structure of Ge_{100 ? x} S _x and Ge_{100 ? x} Se _x glasses enriched in the chalcogen (x ≥ 0.66) is built up of structural units containing twofold-coordinated chalcogen (X) atoms in chains of the

Open image in new window

and

Open image in new window

types, whereas germanium atoms in these glasses have the oxidation state of only +4 and are fourfold-coordinated so that the local environment of the germanium atoms includes only chalcogen atoms. The structure of the glasses depleted in the chalcogen consists of structural units containing twofold-coordinated chalcogen atoms in chains of the

Open image in new window

type and threefold-coordinated chalcogen atoms in chains of the

Open image in new window

type, whereas germanium in these glasses is stabilized both in the oxidation state of +4 and the fourfold-coordinated state and in the oxidation state of +2 and the threefold-coordinated state so that the local environment of the germanium atoms includes only chalcogen atoms.

     

Thermal stability of tin charge states in the structure of the (As<Subscript>2</Subscript>Se<Subscript>3</Subscript>)<Subscript>0.4</Subscript>(SnSe)<Subscript>0.3</Subscript>(GeSe)<Subscript>0.3</Subscript> glass

Two valence states of tin atoms (namely, the doubly charged Sn²⁺ and quadruply charged Sn⁴⁺ states) in the structure of the (As₂Se₃)_0.4(SnSe)_0.3(GeSe)_0.3 glasses are identified by ¹¹⁹Sn Mössbauer spectroscopy. It is demonstrated that the concentration ratio of the doubly charged Sn²⁺ and quadruply charged Sn⁴⁺ states in the glass of this composition depends on the rate of quenching of the melt and on the initial temperature of the melt before quenching. The optical band gap and the activation energy for electrical conduction of the studied glass do not depend on the concentration ratio of the Sn²⁺ and Sn⁴⁺ ions. This behavior of the optical band gap and the activation energy is explained within the model according to which the structure of the glasses under investigation is built up of the structural units AsS_3/2, As_2/2Se_4/4, GeSe_4/2, SnSe_4/2, and SnSe_3/3, which correspond to the compounds AsSe₃, AsSe, GeSe₂, SnSe₂, and SnSe, respectively.     

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.     

Kinetics of stepwise bulk crystallization of AsSe<Subscript>1.5</Subscript>Sn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> (<Emphasis Type="Italic">x</Emphasis> ≤ 0.28) glasses

The kinetics of stepwise transformations during bulk isothermal crystallization of semiconducting AsSe_1.5Sn _x (x = 0.13, 0.20, 0.28) glasses has been studied in the temperature range of 210?310°С using ¹¹⁹Sn Mössbauer spectroscopy, XPA, and the density and microhardness measurements of the quenched specimens. The kinetics of the gross bulk crystallization of glasses have been analyzed according to the data on density measurement using the Kolmogorov–Avrami equation, which was generalized on stepwise and incomplete isothermal transformations.     

Effect of glass composition on the physical properties and luminescence of Pr3+ ion-doped chalcogenide glasses

In this work, Pr³⁺ ion-doped Ge₂₀Ga_15−xSb_xSe₆₅ (x = 0, 5, 10, in mol%), Ge₂₀Sb_15−yIn_ySe₆₅ (y = 5, 10, in mol%), Ge₂₀Ga_15−zIn_zSe₆₅ (z = 0, 5, 10, in mol%), and Ge₂₀Ga₅Sb₁₀Se₆₀I₅ glasses were prepared. The structural units, thermal properties, and optical properties of these glasses were analyzed. In addition, a comprehensive comparison study of the effects of metal ions (Sb, Ga, and In), S/Se ratio, and I content on the mid-infrared (MIR) luminescence of Pr³⁺ ions was conducted. Under a 1.55-μm laser pump, 0.2 mol% of Pr³⁺ ion-doped chalcogenide glasses performed strong photoluminescence in the wavelength range of 3.5-5.5 μm. Results indicated that the Sb-containing glass performed the strongest emission intensity among the studied glasses. Moreover, halogen element I can reduce the phonon energy of the matrix, which is beneficial to the luminescence of Pr³⁺ ions and provide significant possibilities for developing MIR lasers and amplifiers.     

The state of iron and tin atoms in the Ge28.5Pb15S56.5 and Ge27Pb17Se56 vitreous semiconductors

Tin impurity atoms occupy substitutional positions of lead and germanium in the structural network of Ge_28.5Pb₁₅S_56.5 and Ge₂₇Pb₁₇Se₅₆ glasses and are electrically inactive centers. Iron impurity atoms form donor levels in the mobility gap of the glasses and bring about a shift of the Fermi level from the midpoint of the mobility gap. This shift depends on the iron content.     

Determination of the quantitative composition of As-Se and Ge-Se glasses and films by X-ray fluorescence analysis

A method of standards has been proposed for determining the quantitative contents of germanium, arsenic, and selenium in vitreous samples and films of the As_{1 − x} Se _x and Ge_{1 − x} Se _x compositions with the use of X-ray fluorescence analysis. The application of this technique makes it possible to determine the quantitative composition of As_{1 − x} Se _x and Ge_{1 − x} Se _x glasses and films with an accuracy of ±0.001 with respect to the parameter x.     

Composition determination of multicomponent chalcogenide glassy semiconductors with X-ray fluorescence analysis

The standard method-recording of X-ray fluorescence spectra of a standard Ge_0.2As_0.4Se_0.4 alloy followed by evaluation of its component spectral fractions and by building of dependences x _XRF = f(x) and y _XRF = f(y) for the As _x (Ge _y Se_{1 ? y} )_{1 ? x} system—was employed to determine the quantitative contents of arsenic, germanium, and selenium in the Ge _t As _s Se_{1 ? t ? s} glassy alloys with X-ray fluorescence analysis. The accuracy of the composition’s determination was ±0.0005 for both x and y. However, it was not possible to use the external standard method for determining the tellurium in As _y Se_{1 ? y} )_{1 ? x} Te _x alloys because tellurium, arsenic, and selenium had significantly different X-ray fluorescence characteristics and, hence, substitution of the arsenic or selenium for tellurium at a fixed y resulted in tellurium emission fraction changing.     

Optical studies of Se-Bi-Te-Sb thin films by single transmission spectrum

Chalcogenide glasses are interesting materials on account of their infrared application. In present paper, thin films of quaternary chalcogenide glasses, Se_80.5Bi_1.5Te_{18 ? x} Sb _x , where x = 0, 2, 4, has been investigated for their optical properties using transmission spectra in the spectral range of 500–2500 nm. The refractive index shows the normal dispersion behavior and found to increase with increase in Sb content. Extinction coefficient has been observed decreases with Sb content.     

Crystal Structure,Chemical Bonding and Magnetism Studies for Three Quinary Polar Intermetallic Compounds in the (Eu1?xCax)9In8(Ge1?ySny)8 (x = 0.66, y = 0.03) and the (Eu1?xCax)3In(Ge3?ySn1+y) (x = 0.66, 0.68; y = 0.13, 0.27) Phases

Three quinary polar intermetallic compounds in the (Eu_1−xCa_x)₉In₈(Ge_1−ySn_y)₈ (x = 0.66, y = 0.03) and the (Eu_1−xCa_x)₃In(Ge_3-ySn_1+y) (x = 0.66, 0.68; y = 0.13, 0.27) phases have been synthesized using the molten In-metal flux method, and the crystal structures are characterized by powder and single-crystal X-ray diffractions. Two orthorhombic structural types can be viewed as an assembly of polyanionic frameworks consisting of the In(Ge/Sn)₄ tetrahedral chains, the bridging Ge₂ dimers, either the annulene-like “12-membered rings” for the (Eu_1−xCa_x)₉In₈(Ge_1−ySn_y)₈ series or the cis-trans Ge/Sn-chains for the (Eu_1−xCa_x)₃In(Ge_3−ySn_1+y) series, and several Eu/Ca-mixed cations. The most noticeable difference between two structural types is the amount and the location of the Sn-substitution for Ge: only a partial substitution (11%) occurs at the In(Ge/Sn)₄ tetrahedron in the (Eu_1−xCa_x)₉In₈(Ge_1−ySn_y)₈ series, whereas both a complete and a partial substitution (up to 27%) are observed, respectively, at the cis-trans Ge/Sn-chain and at the In(Ge/Sn)₄ tetrahedron in the (Eu_1−xCa_x)₃In(Ge_3−ySn_1+y) series. A series of tight-binding linear muffin-tin orbital calculations is conducted to understand overall electronic structures and chemical bonding among components. Magnetic susceptibility measurement indicates a ferromagnetic ordering of Eu atoms below 5 K for Eu_1.02(1)Ca_1.98InGe_2.87(1)Sn_1.13.     

Evolution of microstructure,optical, and magnetic properties in multiferroic CuFe1-xSnxO2 (x = 0–0.05)

Evolution of the microstructure, optical, and magnetic properties have been investigated systematically in multiferroic CuFe_1-xSn_xO₂ (x?=?0–0.05) ceramics. Substitution of Sn⁴⁺ for Fe³⁺ results in expansion of CuFeO₂ lattice, and reduces the density of the material, but the metal oxidation states are unchanged. Observation of the optical properties shows that the value of the direct optical band gap (E_g) decreases with increasing Sn doping level, and that the CuFe_1-xSn_xO₂ (x?=?0–0.04) series with values >?3.1?eV. Magnetic susceptibility measurements show that Sn⁴⁺ doping decreases the Curie-Weiss temperature, i.e. weakens the strength of the antiferromagnetic interaction between high-spin Fe³⁺ ions, but does not affect the stability of the antiferromagnetic phase, and all samples undergo successive magnetic transitions at about T_N1 =?15?K and T_N2 =?11?K. However, magnetization curves show that changes occur in the magnetic interactions and both ferromagnetism and antiferromagnetism co-exist in the Sn⁴⁺-doped samples. The maximum value of the saturation magnetization of 1.8?emu·g^?1 was observed for the x?=?0.03 sample in a 2.5?kOe field. The changes in the magnetic behavior are closely related to the lattice distortion and charge compensation, which are discussed in detail in this work.     

Refining the phase diagram of PbZr1−x−ySnxTiyO3 ceramics with 0.40≤x≤0.54 by crystal structural,dielectric response and hysteresis loop investigations

Ceramics of PbZr_1−x−ySn_xTi_yO₃ (PZST100x/100y) with 0.40≤x≤0.54 were synthesized via conventional solid state reaction and their crystal structures, dielectric response, and hysteresis loops were systematically investigated. A more precise range of the antiferroelectric/ferroelectric phase boundary of PZST100x/100y ceramics with 0.40≤x≤0.54 was established compared with the results reported by Jaffe. It was found that the introduction of Ti⁴⁺stabilized the ferroelectric order, and Sn⁴⁺substitution enhanced the antiferroelectric order. Thus, the system properties could be tailored by altering Sn and Ti concentration. In addition, the hydrostatic pressure-induced ferroelectric-to-antiferroelectric phase transition was also studied. It has been clarified that the critical transition pressure (P_t) increased with an increasing Ti content at a fixed Sn content.     

The origin of the electrical inactivity of iron and tin impurity atoms in crystalline and vitreous alloys A III B IV (A = Ga, In; B = Te, S)

Tin and iron impurity atoms in the structure of crystalline and vitreous alloys Ga_1?y Te_y (y = 0.6, 0.8) and In_1?y Te_y (y=0.6) are shown to be stabilized in their normal valence states. It is demonstrated that the electrical inactivity of tin and iron impurity ions is caused by the compensating effect of Ga⁺ and In⁺ ions, which are responsible for the fixed position of the Fermi level at the midpoint of the band gap. Tin impurity ions in the structure of the β-In₂S₃ crystal are analogs of two-electron centers (with a negative Hubbard energy) proposed for chalcogenide glasses. Within this model, Sn²⁺ ions are ionized acceptors and Sn⁴⁺ ions are ionized donors.     

Microhardness and optical property of chalcogenide glasses and glass-ceramics of the Sn–Sb–Se ternary system

The microhardness of chalcogenide glasses (ChGs) of the Sn–Sb–Se (SSS) ternary system was investigated, and the correlation of microhardness with the mean coordination number of the SSS ChGs was determined. To prepare infrared-transparent SSS glass-ceramics (GCs), two SSS ChGs (A, Sn_6.23Sb_14.11Se_79.66; B, Sn_9.8Sb_17.22Se_72.98; by molar composition) were selected and thermally treated at 433 and 448 K, respectively. The improved microhardness (with values that increased by 11.5% and 7.3% for SSS ChG A and B, respectively) of the resulting SSS GCs is attributed to the formation of Sb₂Se₃ nanocrystals.     

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.