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1.
Glass Formation and Properties of Chalcogenide Systems. XIX. Glass Formation of HgSe with Germanium Selenides Glass formation is found in the System HgSe? GeSe? GeSe 2 in a large range of composition. The dependence of properties such as glass transition temperature, mole volume, mole polarization, and electrical conductivity on composition suggests a remarkably lower modifier function of HgSe on the germanium selenide glasses in comparison to PbSe. Two regions which are characterized by different structural units in the glass can be deduced from the curves. Annealing results in the formation of the new compound Hg 2 GeSe 3 as well as of two phases which could not be identified up to now. In special limits of composition HgSe/GeSe melts form glasses, too. 相似文献
2.
Some of the properties of glasses obtained in the systems TeO 2–MoO 3 and TeO 2–MoO 3–V 2O 5 had been studied. A good correlation between the properties and the phase diagram of the TeO 2–MoO 3 system was established. The glass resistance-composition function varied between 6.85 · 10 9 ohm · cm and 2.93 · 10 10 ohm · cm. The isolines of the properties (softening temperature, density, resistance at room and higher temperatures and activation energy) of the glasses obtained from the TeO 2–MoO 3–V 2O 5 system were ploted. The electrical resistance is influenced by the concentration of V 2O 5 and MoO 3 and by temperature. The glass absorption characteristics of thin layers were determined in the visible range. 相似文献
3.
The dc and ac electrical conductivity of barium tellurite borate glass doped with Nd 2O 3 in the composition 50 B 2O 3- (20-X) BaO- 20TeO 2 10 LiF or Li 2O where x = 0.5, 1, 1.5 and 2 Nd 2O 3 were measured in the temperature range 303–648 K and in the frequency range 0.1–100 kHz. The dc and ac conductivities values increase, whereas the activation energy of conductivities decreases with increasing Nd 2O 3 content in the glasses containing LiF and by the replacement of LiF by Li 2O the conductivity was found to decrease with addition of Nd 2O 3. The electrical conduction has been observed to be due to small polaron hopping at high temperatures. The frequency dependence of the ac conductivity follows the power law σAC ( ω) = A ωs. The frequency exponent ( s) values (in the range 0.94 and 0.33) decreases with increasing temperature. The dielectric constant and dielectric loss increased with increasing temperature and decreased with increase in frequency for all glasses studied. In LiF glasses, it is observed that, the values of ? \ and tan δ are observed to increase with the addition of Nd 2O 3 whereas they decrease in the glasses containing Li 2O. The electrical modulus formalism has been used for studying electrical relaxation behavior in studied glasses. It is for first time that the Nd 2O 3 doped barium tellurite borate glasses have been investigated for dc and ac conductivities and dielectric properties over a wide range of frequency and temperature. 相似文献
4.
New fluoride glasses were obtained in the InF 3-BaF 2-YF 3 system. Evidence for phase separation was found in this basic ternary system, suggesting that glasses based on yttrium fluoride could be formed. Indeed such glasses could be prepared by fast cooling. The mean sample thickness was 2–3 mm. Glass transition, crystallization and melting temperatures were measured. 相似文献
5.
Rare earth (Er 3+ and Nd 3+) ions doped cadmium lithium boro tellurite (CLiBT) glasses were prepared by melt quenching method. The vis–NIR absorption spectra of these glasses have been analyzed systematically. Judd–Ofelt intensity parameters Ω λ ( λ = 2, 4, 6) have been evaluated and used to compute the radiative properties of emission transitions of Er 3+ and Nd 3+: CLiBT glasses. From the NIR emission spectra of Er 3+: CLiBT glasses a broad emission band centered at 1538 nm ( 4I 13/2 → 4I 15/2) is observed and from Nd 3+: CLiBT glasses, three NIR emission bands at 898 nm ( 4F 3/2 → 4I 9/2), 1070 nm ( 4F 3/2 → 4I 11/2) and 1338 nm ( 4F 3/2 → 4I 13/2) are observed with an excitation wavelength λexci = 514.5 nm (Ar + Laser). The FWHM and stimulated emission cross-section values are calculated for Er 3+ and Nd 3+: CLiBT glasses. FWHM × σeP values are also calculated for Er 3+: CLiBT glasses. 相似文献
6.
A physicochemical study of glasses based on the MO-Bi 2O 3-B 2O 3 and SrO-Bi 2O 3-B 2O 3 systems was performed. Glass formation regions were found. The structural and optical properties, as well as the thermal
behavior of the glasses, were studied. 相似文献
7.
Glass Formation and Properties of Chalcogenide Systems. IX. On the Structure of GeS/GeS 2 and GeSe/GeSe 2 Glasses Mole volume, glass transition temperature, and coefficient of thermal expansion were measured on glasses prepared by standardized conditions. Near the composition Ge 2S 3 and Ge 2Se 3 the properties show a singularity or point of inflexion, respectively. Random models of structure are inconsistent with such a behaviour. A model of higher chemical order is proposed which can explain the observed dependence of the glass properties on composition and is in accordance with radial distribution studies. 相似文献
8.
The optical properties of fluorohafnate glasses doped with Pr 3+, Nd 3+, Sm 3+, Dy 3+, Ho 3+, Er 3+, and Tm 3+ have been studied. From optical absorption measurements and using Judd-Ofelt theory, JO parameters Ω 2, Ω 4, and Ω 6 have been obtained. The Ω 2 values indicate that fluorohafnate glasses present a less ionic character than fluorozirconates. Multiphonon emission probabilities for several levels of Er 3+ and Ho 3+ ions were determined by the difference between the measured rates and the calculated radiative transition probabilities. The results are almost the same as those found in fluorozirconates. Multiphonon emission probabilities are in agreement with the energy-gap law followed by rare-earth ions in crystals and glasses. 相似文献
9.
The boundaries of tellurite glasses in the PbCl 2-MoO 3-TeO 2 system have been determined. Glass samples have been synthesized, and their spectroscopic (IR) and electrophysical (resistance versus temperature) properties have been studied. 相似文献
10.
Judd-Ofelt parameters obtained from the absorption spectra of Eu 3+ ions doped in PbO-PbF 2 glasses are intermediate between the values for fluoride and phosphate glass matrices. Eu 3+ ions are coordinated to both oxide and fluoride ions. The calculated transition probabilities (As -1) for the laser transition 5D o→ 7F 2 are 171 and 170 for 30PbO-70PbF 2 and 70PbO-30PbF 2 glasses respectively and are significantly lower compared to phosphate glasses. The calculated (β R cal) and experimental (β Rexpt) branching ratios for this transition show good agreement. The emission spectra display high energy transitions in the
440–570 nm region, a characteristic of parent matrices with low energy phonons such as the tellurite, germanate and fluoride
glasses. The electron-phonon coupling strengths deduced from the excitation spectra of Eu 3+ are 10.2 x 10 −3 and 9.5 x l0 −3 for 30PbO-70PbF 2 and 70PbO-30PbF 2 glasses respectively. The relative emission intensities of the low energy transitions to high energy transitions and the
ratios of the most intense transitions 5D 0→ 7F 2/ 5D 0→ 7F 7 significantly vary for the two glasses providing evidence for clustering of Eu 3+ ions with increase in its concentration and increasing PbO content. 相似文献
11.
Iron phosphate-silicate glasses from P2O5–SiO2–K2O–MgO–CaO–Fe2O3 system were subjected to the thermal and spectroscopic studies in order to gain information about their structure and thermal behavior in the range of glass transition effect. Research includes results obtained via DSC, MIR and DRIFT spectroscopy. Designated values of glass transition temperature and specific heat change slightly increases with Fe2O3 incorporation. Spectra collected during thermal treatment of glasses containing 2 and 30 mol% Fe2O3 exhibited various changes. Fe2O3 addition affected the glass structure by its reinforcement and led to its preservation during thermal treatment. The connection between density, molar volume, oxygen packing density and the chemical composition’s alteration were also established because of the direct dependence of physical properties and the structure. Obtained results supported thermal and spectroscopic studies. Conducted research is considered as a contribution to the knowledge about the family of iron phosphate glasses, which are known from their interesting properties and widely used applications. 相似文献
12.
A series of Na2O-MgO-TiO2-Al2O3-B2O3-SiO2 glasses promising as sealants for solid oxide fuel cells are prepared. The glassy state is confirmed by X-ray diffraction analysis, and the elemental composition is determined by inductively coupled plasma atomic emission spectroscopy. The coefficient of thermal expansion (CTE) is calculated from the dilatometric data; it varies within (69–77) × 10?7 K?1 and increases with the MgO to Al2O3 concentration ratio. The CTE calculation by the Appen method gives the results that are underestimated by 5–8% relative to the experimental data. The temperature dependences of the heat capacity of the glasses are determined by differential scanning calorimetry and calculated using the Kopp-Neumann rule. Comparison of the calculated values with the experimental data shows that the Kopp-Neumann rule is observed for the systems under consideration with relatively high accuracy. The sensitivity of different methods in determination of the glass transition point has been evaluated. 相似文献
13.
The distribution of Q-units of CaO–P 2O 5 glasses was described by the thermodynamic model of Shakhmatkin and Vedishcheva. The glass was considered as the ideal solution of CaO, P 2O 5, CaP 2O 6, Ca 2P 2O 7, and Ca 3P 2O 8. 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. 相似文献
14.
The electrical conductivity of oxyfluoride glasses in the MnNbOF 5-BaF 2-BiF 3 system in the temperature range 299–550 K was studied by impedance spectroscopy. It was shown that the conductivity is mainly caused by fluoride ions forming fluorobismuth polyhedra in the glass structure, being as high as 7.46 × 10 ?3 S/cm (533 K) in the 20MnNbOF 5-30BaF 2-50BiF 3 system reaches, which is at the level of the best values for fluoride glasses. 相似文献
15.
Investigations on Electronically Conducting Oxide Systems. I. Glass Formation in the System K 2O? SiO 2? VO 2 Glass formation in the system K 2O-SiO 2-VO 2 was investigated. The glass forming region is compared with the glass formation in the system K 2O-SiO 2-TiO 2. Density and electrical conductivity of the glasses are discussed in denpendence on the composition. 相似文献
16.
Rates, Arrhenius parameters, and Hammett substituent constants are obtained for the gas-phase thermal elimination of ethyl benzoate (1) and ethyl 2—thienyl— (2), 3—thienyl— (3), 2—furyl— (4), 3—furyl— (5), 4—pyridyl— (6), 3—pyridyl— (7), and 2—pyridylcarboxylate (8) esters. The log A/s −1 and the E a/kJ mol −1 values of these esters averaged 13.60 and 216.3, respectively. The present results are compared with data previously reported for the corresponding isopropyl and t-butyl analogues, and the findings are rationalized in terms of a plausible transition state for the elimination pathway. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 289–293, 1997. 相似文献
17.
Full validation of the electrochemical mechanisms so far postulated as driving force of electric field-assisted non-spontaneous
crystallization development in given glasses has suffered experimental restrictions. In this work, we looked into origin of
this phenomenon in lead oxyfluoroborate glasses, resulting in β-PbF 2 growth even below the corresponding glass transition temperatures, through achieving a systematic study of not only Pt,Ag/Glass/Ag,Pt-
but also Pt,Ag/Glass/YSZ:PbF 2/Ag,Pt-type cells, where YSZ:PbF 2 represents a two-phase system (formed by Y 2O 3-doped ZrO 2 and PbF 2). It is demonstrated that crystallization induction in these glasses involves Pb 2+ ions reduction at the cathode, the phenomenon being, however, confirmed only when the F − ions were simultaneously also able to reach the anode for oxidation, after assuring either a direct glass–anode contact or
percolation pathways for free fluoride migration across the YSZ:PbF 2 mixtures. A further support of this account is that the electrochemically induced β-PbF 2 phase crystallizes showing ramified-like microstructure morphology that arises, accordingly, from development of electroconvective
diffusion processes under electric field action. 相似文献
18.
Glasses of the MnNbOF 5–BaF 2–InF 3 system were prepared. The structure, thermal behavior, and crystallization of these glasses were studied by IR and Raman spectroscopy, differential scanning calorimetry (DSC), X-ray powder diffraction, and microscopy. The \(\rm{NbO}_2\rm{F}_4^{3-}\) and \(\rm{InF}_6^{3-}\) ions form a mixed glass network. Glass crystallization occurs in one or two steps depending on the component ratio. The major crystal phases are Ba 3In 2F 12 and BaNbOF 5. The obtainability of transparent crystal-glass samples in MnNbOF 5–BaF 2–InF 3 glasses via heat treatment is shown. 相似文献
19.
The subject of the study was silicate–phosphate glasses of NaCaPO 4–SiO 2 system which are precursors of glass–crystalline materials. Glass–crystalline materials of NaCaPO 4–SiO 2 system obtained via crystallization of glasses belong to a group of the so-called bioactive materials. In order to obtain glass–crystalline materials with pre-established parameters, it is necessary to conduct crystallization of glasses at specific conditions. In order to design direct crystallization process properly, it is necessary to know the structure and microstructure of the glassy precursor. Microscopic investigation showed that liquation takes place in all the studied glasses. Based on DSC examinations, it has been found out that crystallization of the glasses of NaCaPO 4–SiO 2 system is a multistep process. The presence of several clearly separated exothermic peaks in DSC curves of investigated glasses makes it possible to crystallize only the separated phase with the matrix remaining amorphous or vice versa. Conducted detailed X-ray and spectroscopic studies of the materials obtained by heating in a gradient furnace (in the temperature specified on the basis of DSC) showed that separated phase and matrix crystallizes separately. Therefore, bioactive glass–crystalline materials can be obtained due to the existence of the phase separation phenomenon and pre-established sizes of the crystalline phase. 相似文献
20.
Tin-119m Mössbauer and selected infrared and 1H NMR data are reported for twenty four triorganotin derivatives of substituted pyridines and related ligands, and conclusions concerning structure inferred. Mössbauer quadrupole splittings in the ranges 3.09–3.38 mm sec ?1 and 2.92–3.22 mm sec ?1, respectively, for the 2- and 3-pyridone derivatives indicate five-coordinate trans-R 3SnX 2 trigonal bipyramidal configurations at tin with planar R 3Sn moieties. In the case of the derivatives of 2-pyridone, the extra coordination to give linear chain structures arises from bridging oxygen atoms, but bridging via either oxygen or the pyridyl nitrogen atom may occur in the derivatives of 3-pyridone. Similar oxygen-bridged chain structures are also postulated for the triorganotin derivatives of 2-pyridylalcohol and 2-pyridylaldehyde oxime, but lower splittings values of 2.63(5)–2.93 mm sec ?1 indicate some relaxation from planarity of the R 3Sn group towards tetrahedral. The splittings are observed to decrease in the order Me > Et > Pr, illustrating that the deviation from planarity and the bond distance of the coordinate O?Sn bond increase with the steric bulk of R. Much lower splittings of 1.60–2.27 mm sec ?1 are observed for the derivatives of 2-thiopyridone and 8-hydroxyquinoline, which, with the presence of three tin—carbon stretching modes in the infrared spectrum for the methyltin compounds, are consistent with the alternative five-coordinate cis-R 3SnX 2 geometry at tin. The very high splitting values, together with the low values of the anti-symmetric OCO stretching vibration of the carboxylate group and the multiple tin—carbon stretching modes observed for the methyltin compounds in the infrared, have been interpreted in terms of the six-coordinate mer-R 3SnX 3 stereochemistry for the triorganotin esters of 2-pyridylcarboxylic and 2,6-pyridyldicarboxylic acids. The low and almost constant value of the two-bond coupling constant 2J( 1HC 119Sn) for the methyltin derivatives indicate that n solution either four or five-coordinate cis-R 3SnX 2 structures are adopted. 相似文献
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