Thermodynamic model and Raman spectra of MgO–P2O5 glasses

Journal of Thermal Analysis and Calorimetry - The structure of binary glasses xMgO·(1?x)P2O5 (x?=?0.30, 0.35, 0.40, 0.45, 0.50, and 0.55) was studied by thermodynamic model...     

Correction to: Thermodynamic model and Raman spectra of MgO–P2O5 glasses

Journal of Thermal Analysis and Calorimetry - Convection heat transfer in cavities has attracted much attention from researchers. Many kinds of nanofluids have exhibited non-Newtonian behavior and...     

Thermodynamic properties of two zinc borates: 3ZnO·3B2O3·3.5H2O and 6ZnO·5B2O3·3H2O

Two pure zinc borates with microporous structure 3ZnO·3B₂O₃·3.5H₂O and 6ZnO·5B₂O₃·3H₂O have been synthesized and characterized by XRD, FT-IR, TG techniques and chemical analysis. The molar enthalpies of solution of 3ZnO·3B₂O₃·3.5H₂O(s) and 6ZnO·5B₂O₃·3H₂O(s) in 1 mol · dm⁻³ HCl(aq) were measured by microcalorimeter at T = 298.15 K, respectively. The molar enthalpies of solution of ZnO(s) in the mixture solvent of 2.00 cm³ of 1 mol · dm⁻³ HCl(aq) in which 5.30 mg of H₃BO₃ were added were also measured. With the incorporation of the previously determined enthalpy of solution of H₃BO₃(s) in 1 mol · dm⁻³ HCl(aq), together with the use of the standard molar enthalpies of formation for ZnO(s), H₃BO₃(s), and H₂O(l), the standard molar enthalpies of formation of −(6115.3 ± 5.0) kJ · mol⁻¹ for 3ZnO·3B₂O₃·3.5H₂O and −(9606.6 ± 8.5) kJ · mol⁻¹ for 6ZnO·5B₂O₃·3H₂O at T = 298.15 K were obtained on the basis of the appropriate thermochemical cycles.     

Vibrational spectra of Na3SbS4, Na3SbS4·9H2O (Schlippe's salt) and Na3SbS4·9D2O

Powder Raman and far i.r. spectra of Na₃SbS₄ and single crystal Raman and powder i.r. spectra of Na₃SbS₄·9H₂O(D₂O) (Schlippe's salt) were measured in the temperature range T = 75–295 K. Assignments are given for internal SbS₄ and H₂O(D₂O) vibrations. The OH(D) stretching frequencies, ν̄ = 3309(2449)–3422(2550) cm⁻¹, support the existence of a marked hydrogen bond system not only between different water molecules, but also between the hydrate water molecules and the sulphur atoms of the SbS₄ groups in Schlippe's salt.     

Synthesis and thermochemical characteristics of Na2O · Al2O3 · 2.5H2O

A pure phase of monosodium aluminate hydrate Na₂O · Al₂O₃ · 2.5H₂O (MAH) is synthesized and characterized by means of XRD, IR, SEM, TGA, and DSC. The heat capacity of the compound is measured in the temperature range of ?100 to 100°C, and the thermal contributions to enthalpy and entropy are calculated. The standard entropy, enthalpy, and Gibbs energy of formation of MAH at 298 K are estimated.     

Synthesis and Thermodynamic Properties of MgO·B_2O_3·4H_2O

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Thermodynamic model and structure of CaO–P2O5 glasses

The distribution of Q-units of CaO–P₂O₅ glasses was described by the thermodynamic model of Shakhmatkin and Vedishcheva. The glass was considered as the ideal solution of CaO, P₂O₅, CaP₂O₆, Ca₂P₂O₇, and Ca₃P₂O₈. In the first step, molar Gibbs energies of considered species were taken from the FACT thermodynamic database. The obtained result was compared with ³¹P solid-state NMR study of Roiland. It was shown that the calculated values were in fairly good agreement with the experimental values. After that, the nonlinear regression treatment was used for optimization of molar Gibbs energies by minimizing the sum of squares of deviations between experimental and calculated Q-distribution. In such a manner, the non-ideality of the system was reflected. In the studied case, no significant improvement of obtained results was achieved by this procedure—thus, the ideal solution assumption included in the thermodynamic model of Shakhmatkin and Vedishcheva holds very well for the studied binary glasses.     

IR and polarized Raman spectra of K2Mg(SO4)2 · 6H2O

IR and polarized Raman spectra of K₂Mg(SO₄)₂ · 6H₂O have been recorded and analyzed. From the spectra, the vibrations due to SO²⁻₄ ion, the complex [Mg(H₂O)₆]²⁺ and the water molecules have been identified. The splitting of the nondegenerate ν₁ mode of the SO²⁻₄ ion indicates the presence of a factor group interaction between vibrating ions in the crystal. It has been inferred that the angular distortion of SO²⁻₄ is greater than the bond distortion. Separate bands for the three different water molecules have been observed.     

Crystal structure and Raman spectra of [Fe(H2O)6]3+(ClO 4 ? )3·3H2O

Single crystal X-ray diffraction is used to study the structure of colorless crystals isolated from the saturated aqueous solution of trivalent iron perchlorate (TIP) in 67.5% perchloric acid. It is found that the compound crystallizes in the trigonal crystal symmetry; parameters of the hexagonal unit cell: a = b = 16.079(2) ?, c = 11.369(2) ?, ?? = ?? = 90°, ?? = 120°, space group R{ie907-1}(S ₆), Z = 6, ??_calc = 2.021 g/cm³. The structural form of the crystal hydrate is [Fe(H₂O)₆]³⁺(ClO ₄ ^? )₃·3H₂O. The structure contains two independent complex iron cations. Each of them is in the special position {ie907-2}, but retains the regular octahedral structure: average bond lengths are r(Fe-O) = 1.997(1) ?, {ie907-3}O-Fe-O bond angles differ from 90° by only 0.93°. Independent [Fe(H₂O)₆]³⁺ cations form short H-bonds (O??O 2.64 ?) with three crystallization water molecules and somewhat longer H-bonds (O??O 2.73 ?) with three ClO ₄ ^? anions. The ClO ₄ ^? anion is disordered over two positions with occupancies of 0.62(2) and 0.37(2). Both positions correspond to the general position. The outer-sphere crystallization water molecule is characterized by the tetrahedral direction of H-bonds, which it forms with two anions and two independent [Fe(H₂O)₆]³⁺ cations. All water molecules are in the general position. The Raman spectroscopic study of polycrystalline samples reveals weak bands belonging to the internal vibrations of two types of water molecules. The least broad bands are assigned to the transitions of crystallization water molecules whose symmetry is insignificantly lowered by two anion-molecular Hbonds. Anomalously broad bands are assigned to the transitions of a coordinated water molecule whose symmetry is more lowered by intermolecular and anion-molecular H-bonds.     

Infrared,Raman and XPS spectroscopic studies of Bi2O3–B2O3–Ga2O3 glasses

Glasses with compositions 60Bi₂O₃–(40?x)B₂O₃–xGa₂O₃ (x = 5, 10, 15, 20 mol%) are prepared by conventional melting method. The thermal properties are investigated by differential thermal analysis (DTA) and the structures of the glasses were probed by Infrared, Raman and X-ray photoelectron spectroscopy (XPS). The results show that density, refractive index and optical basicity increase with the increase of Ga₂O₃. The glass transition temperature (T_g), the onset crystallization temperature (T_x), ΔT (T_x?T_g) decrease with the content of Ga₂O₃. The cut-off edges in ultraviolet and infrared shift to longer wavelength with the increase of Ga₂O₃. On the other hand, the addition of Ga₂O₃ causes a progressive coordination number change of the boron atom from 3 to 4. XPS result indicates both Bi⁵⁺ and Bi³⁺ exist in 5 mol% Ga₂O₃ content, while Bi⁵⁺ amounts decrease with the increase of Ga₂O₃ contents. The glass is mainly composed of [BiO₆], [BO₃], [BO₄] and [GaO₄] polyhedra. Glasses are supposed to have layer structure. [BO₃] triangle and [BO₄] tetrahedra may be located between the [GaO₄] tetrahedral and [BiO₆] octahedra to prevent crystallization and to compensate electric charge.     

209Bi NQR in Mixed Oxides 2Bi2O3· B2O3, 3Bi2O3· 5B2O3, and Bi2O3· 3B2O3

It was earlier found from nuclear quadrupole resonance (NQR) measurements and computer modeling that -Bi₂O₃, Bi₃O₄Br and mixed oxides Bi₂O₃· 2Al₂O₃, Bi₂O₃· 2Ga₂O₃, Bi₂O₃· 3GeO₂, and 2Bi₂O₃· 3GeO₂exhibit local ordered magnetic fields from 30 to 200 G. It thus follows that these compounds are not diamagnets in a conventional sence of the word. With the aim of revealing previously unknown magnetic properties in bismuth(III) oxide-based Main Group element compounds, the mixed bismuth–boron oxides 2Bi₂O₃· B₂O₃, 3Bi₂O₃· 5B₂O₃, and Bi₂O₃· 3B₂O₃were prepared and studied using ²⁰⁹Bi NQR. The quadrupole interactions of the ²⁰⁹Bi nuclei and their electronic environment were studied, the crystallochemical features of the compounds were discussed, and the conformity of the ²⁰⁹Bi results to the X-ray structure data was verified. The preliminary tests in the field of a permanent magnet showed that the resonance intensities increase in external magnetic fields, indicating that a magnetism of unknown nature develops in the titled compounds. It was found reasonable to continue studies of the magnetic properties of these compounds using single-crystal ²⁰⁹Bi NQR in external magnetic fields.     

Infrared,Raman and XPS spectroscopic studies of Bi2O3–B2O3–GeO2 glasses

Glasses with composition 50Bi₂O₃–(50 ? x) B₂O₃–xGeO₂ (x = 0, 5, 10, 15 mol%) were prepared by conventional melting method. The thermal properties were investigated by differential thermal analysis (DTA) and the structures of the glasses were probed by Infrared, Raman and X-ray photoelectron spectroscopy (XPS). The results show that density, refractive index and optical basicity increase with the increase of GeO₂. The glass transition temperature (T_g), onset crystallization temperature (T_x) and ΔT (T_x ? T_g) increase as well. The cut-off edges in ultraviolet and infrared shift to longer wavelength by the addition of GeO₂. Infrared, Raman and XPS results indicate that the glass network consists of [Bi–O₆] octahedron, [BO₃] triangle, [BO₄] tetrahedron and [GeO₄] tetrahedron and borate oxide mainly exists in [BO₃] units. XPS result indicates Ge⁴⁺ ions form steady [GeO₄] tetrahedra units in the glass network and the number of non-bridging oxygens decreases with the addition of GeO₂.     

Magnetic and optical investigation of 40SiO2·30Na2O·1Al2O3·(29 − x)B2O3·xFe2O3 glass matrix

Samples of 40SiO₂·30Na₂O·1Al₂O₃·(29 − x)B₂O₃·xFe₂O₃ (mol%), with 0.0 ≤ x ≤ 17.5, were prepared by the fusion method and investigated by electron paramagnetic resonance (EPR), optical absorption (OA) and Mössbauer spectroscopy (MS). The EPR spectra of the as-synthesized samples exhibit two well-defined EPR signals around g = 4.27 and g = 2.01 and a visible EPR shoulder around g = 6.4, assigned to isolated Fe³⁺ ion complexes (g = 4.27 and g = 6.4) and Fe³⁺-based clusters (g = 2.01). Analyses of both EPR line intensity and line width support the model picture of Fe³⁺-based clusters built in from two sources of isolated ions, namely Fe²⁺ and Fe³⁺; the ferrous ion being used to build in iron-based clusters at lower x-content (below about x = 2.5%) whereas the ferric ion is used to build in iron-based clusters at higher x-content (above about x = 2.5%). The presence of Fe²⁺ ions incorporated within the glass template is supported by OA data with a strong band around 1100 nm due to the spin-allowed ⁵E_g–⁵T_2g transition in an octahedral coordination with oxygen. Additionally, Mössbauer data (isomer shift and quadrupole splitting) confirm incorporation of both Fe²⁺ and Fe³⁺ ions within the template, more likely in tetrahedral-like environments. We hypothesize that ferrous ions are incorporated within the glass template as FeO₄ complex resulting from replacing silicon in non-bridging oxygen (SiO₃O⁻) sites whereas ferric ions are incorporated as FeO₄ complex resulting from replacing silicon in bridging-like oxygen silicate groups (SiO₄).     

Thermodynamic properties and amorphization of Zr–Si melts

The relationship between the thermodynamic properties of Zr–Si liquid alloys and their propensity to amorphization is studied. The temperature–concentration dependences of the thermodynamic properties of melts are presented using the concept of associated solutions. It is shown that the range of amorphization coincides with the range of the predominant concentration of Zr₃Si associative groups with low formation entropy.     

Quantifying Raman and emission gain coefficients of Ho3+ doped TeO2·ZnO·PbO·PbF2·Na2O (TZPPN) tellurite glass

Broadband amplifier emission near the second telecommunication window in Ho³⁺ doped 76TeO₂·10ZnO·9.0PbO·1.0PbF₂·3.0Na₂O was studied. The optical transition properties and radiative lifetimes of several excited states of Ho³⁺ have been predicted using intensity Judd–Ofelt parameters. The emission cross section for Ho³⁺ in this glass, around 2 μm, was calculated according to McCumber theory. The maximum stimulated emission cross section was calculated to be 0.9 × 10⁻²⁰ cm² for 2046 nm emissions. The theoretical gain cross sections was evaluated and positive gain bands was anticipated. Furthermore, the peak Raman gain coefficient in the present glass was around 250 times larger than that of SiO₂.     

The i.r. and Raman spectra of sodium hexafluorophosphate monohydrate,NaPF6·H2O

The i.r. and Raman spectra of NaPF₆·H₂O and partially deuterated NaPF₆·H₂O have been obtained. All of the fundamental modes of the PF⁻₆-ion have been located and the rule of mutual exclusion applies for these modes. In the Raman spectra, the number of components observed for each fundamental PF⁻₆-mode is consistent with the number of site group components predicted. The hydrogen bonds in NaPF₆·H₂O are very weak and the hydrogen bond energy is of the order of 1.7 kcal/mole. The frequencies of the nine fundamental modes of the H₂O, D₂O and HDO molecules have been converted to harmonic values. It is shown that if the HOH valence angle is varied, and the effective harmonic force field of the water molecules calculated for each assumed value, an estimated value of this angle in NaPF₆·H₂O can be obtained. The librational modes of the water molecules have been located and are assigned to rocking and wagging modes.     

Preparation and Raman spectra of Ca(NO2)2·H2O,Ca(NO2)2 and Mg(NO2)2·H2O

The above named salts have been prepared from aqueous solutions of the pure nitrates. Distinct compounds Ca(NO₂)₂·H₂O and Ca(NO₂)₂ which are free of nitrate impurity have been characterized by their Raman spectra. The hydrated salt appears to contain four crystallographically non-equivalent nitrate groups. A distinct hydrate of magnesium formulated as Mg(NO₂)₂·H₂O can also be prepared and characterized by Raman spectroscopy but this sample always contained significant nitrate impurity.