Crystallization Behavior of Potassium Niobium Silicate Glasses

Crystallization behavior of potassium niobium silicate (KNS) glasses having compositions expressed by the general formula x K₂O· x Nb₂O₅·(1 - 2 x )SiO₂, with x = 0.167, 0.182, 0.200, 0.220, and 0.250, has been studied by DTA, X-ray diffraction, second harmonic optical generation (SHG), and electron microscopy. Bulk crystallization of potassium niobates in glasses with compositions near K₂O·Nb₂O₅·2SiO₂, as well as surface crystallization of KNbSi₂O₇ phase, has been established. Transparent glass-ceramics, based on potassium niobates with remarkable SHG signal values, can be obtained from glasses with the lowest silica content, by heat treatment at temperatures just above T _g, while at higher temperatures from all of the glasses under investigation the main crystallizing phase is KNbSi₂O₇ ferroelectric. Applying a dc electric field, grain-oriented crystallization is produced in KNS glasses with development of significantly anisotropic arrangements of KNbSi₂O₇ crystallites.     

Spectroscopic and X-ray Diffraction Investigations into the Specific Features of Crystallization of Potassium Niobium Silicate Glasses

The Raman spectra and X-ray diffraction patterns of initial and crystallized glasses of the composition 25K₂O · 27.5Nb₂O₅ · 47.5SiO₂ (mol %) are investigated. It is demonstrated that, upon heat treatment at temperatures in the range 740–900°C, nanocrystals similar in composition to the initial glass precipitate in the glass. The sizes of nanocrystals are estimated with the use of both methods.     

Structure and Nonlinear Optical Properties of Lanthanide Borate Glasses

The third–order nonlinear optical susceptibility, χ⁽³⁾, of lanthanide (lanthanum, praseodymium, neodymium, and samarium) borate glasses has been measured by the third harmonic generation method. The structure of the present glass system has been studied by infrared and Raman spectroscopic methods. The network structures of the present Ln₂O₃–B₂O₃ glasses have been confirmed to be basically similar to each other. Praseodymium, neodymium, and samarium borate glasses exhibit χ⁽³⁾ values that are larger than lanthanum borate glasses, because of the optical resonance effect, in accordance with the f – f transition. Especially, the χ⁽³⁾ value for 30Pr₂O₃·70B₂O₃ glass is 1.8 × 10⁻¹² esu, which is a factor of ∼60 larger than that of SiO₂ glass. This striking enhancement of χ⁽³⁾ is mainly attributed to the large transition moment to the first excitation state.     

Properties of Coatings Obtained in Treatment of Silicate Glasses in Potassium and Lead Nitrate Melts

The effect of the duration of treatment of the surface of soda-lime glass in potassium and lead nitrate melts at a temperature of 460°C on the chemical and mechanical strength is investigated. It is demonstrated that the formation of a crystalline lead-silicate coating in this treatment increases the alkali resistance threefold and the mechanical strength of glass twofold. Practical recommendations are issued.     

Crystallization Behaviors of PbSe Quantum Dots in Silicate Glasses

This study, composed of three parts, aims at studying the crystallization behaviors of PbSe quantum dots (QDs) in silicate host glasses. Firstly, due to the importance of the choice of base glass for the QDs' crystallization, the selection of base glass compositions, the glass fragility, and glass formation ability (GFA) are discussed in details, and the results show that the selected glass compositions have an intermediate fragility and accordingly an intermediate glass transition temperature range among a wide variety of inorganic glass systems together with a good GFA/glass stability (GS). Thus, this base glass is suitable as the host glass in which PbSe QDs crystallize. Secondly, the experimental results on PbSe QDs' crystallizations are presented, and the results show that PbSe QDs can precipitate from silicate glasses favorably with no other chemical compounds precipitation, and the optimized temperature for PbSe QDs crystallization is 600°C. Lastly, the classical nucleation theory is used to analyze the PbSe QD crystallization behaviors in host glasses. The steady‐state nucleation rates and the growth rates of PbSe QDs as well as the time–temperature transformation (TTT) curves are calculated. The results indicate that the free surface energy between the PbSe nuclei and the host glass has great influence on the nucleation rates of PbSe QDs, while it has less effect on the growth rates of PbSe QDs; the crystallization behaviors of PbSe QDs with different volume fractions can be described well by the TTT curves while keeping the dimensionless empirical constant, α, unchanged for one certain curve.     

Electrode Properties of Fluorine-Containing Alkali Silicate Glasses

An attempt is made to change the electrode properties of alkali silicate glasses containing various glass-formers and modifiers by introducing fluorine components into their compositions. Model systems with the initial hydrogen and metallic electrode functions are investigated. The study is based on the assumption that new ionogenic structural units with a mixed-anion constituent are formed in the glass structure. Lithium, sodium, and potassium silicate glasses with different fluorine contents are synthesized. Their potentiometric properties are studied. It is shown that the introduction of fluorine exerts the strongest effect on the electrode properties of alkali aluminosilicate glasses. An indirect corroboration is obtained for the assumption that strongly acid groupings containing fluorine can be formed in the glass network. It is found that the technological properties of the electrode glasses are significantly improved and the chemical durability in the potassium-containing system also becomes much higher. From the results obtained, the inference is drawn about the prospects of fluorine introduction into electrode glasses.     

铌酸钾的合成、表征及性能研究

相比于PZT等铅基压电陶瓷,碱金属铌酸盐陶瓷具有下列特点:介电常数小,压电性高,频率常数大,密度小,因此多年来常被作为电光材料。铌酸钾作为一种典型的铌酸盐化合物,具有良好的催化活性、选择性及稳定性,本文系统介绍了铌酸钾粉体的性质,制备方法、表征以及性能研究的现状。     

Some Structural and Electrical Properties of Lithium Silicate Glasses

Dielectric measurements, analyzed in terms of the Maxwell-Wagner-Sillars theories of inhomogeneous dielectrics, have been used to investigate the phase-separation characteristics of various lithium silicate glasses. Such measurements are shown to provide evidence of the continuous or discontinuous nature of separated phases and to allow estimates of their shape factors and concentrations. The results indicate that dielectric measurements are particularly useful in following phase-separation processes in glasses from the initial to the final stages.     

Optical Properties of Diatomic Glasses

The ability of elements to form glasses, the leading part played by the elements of Group VI (O, S, Se, and Te), and the possible influence of the elements of Group VII (F, Cl, Br, and I) are discussed. New glasses suggested by previous work were melted and the refractive index ( n ) and coefficient of dispersion ( v ) of some of them were measured. Inspection of the n, v plots of oxide, sulfide, selenide, and telluride glasses shows that the area corresponding to them extends toward high values of refractive index ( n _max= 5.3) and low values of dispersion coefficient ( v _min=4).     

Optical Properties and Effect of Gamma Irradiation on Bismuth Silicate Glasses Containing SrO, BaO or PbO

Optical and FT Infrared spectroscopic measurements have been utilized to investigate and characterize binary bismuth silicate glass together with derived samples by replacements of parts of the Bi₂O₃ by SrO, BaO, or PbO. This study aims to justify and compare the spectral and shielding behavior of the studied glasses containing heavy metal ions towards gamma irradiation. The study also aims to measure or calculate the optical energy band gap of these glasses. The replacements of parts of Bi₂O₃ by SrO, BaO or PbO caused some changes within the optical and infrared absorption spectra due to the different housing positions and physical properties of the respective divalent Sr2+, Ba2+, Pb2+ ions. The stability of both the optical and infrared spectra of the studied bismuth silicate glass and related samples towards gamma irradiation confirm some shielding behavior of the studied glasses and their suitability as radiation shielding candidates.     

Properties and Crystallization Behavior of Sodium Iron Phosphate Glasses

Ternary Na₂O–Fe₂O₃–P₂O₅ (NFP) glasses with varying Na₂O/Fe₂O₃, Na₂O/P₂O₅, and Fe₂O₃/P₂O₅ ratios were prepared. The properties and crystallization tendencies were systemically investigated. It is shown that both density and chemical stability of the glass increase with Fe₂O₃. In contrast the Na₂O/P₂O₅ ratio has little effect on the glass properties for a fixed Fe₂O₃ content. The crystallization behavior of the glasses was analyzed by DTA and XRD. Unlike Li₂O–Fe₂O₃–P₂O₅ glasses NFP glasses were found to be stable against crystallization. 15Na₂O–27Fe₂O₃–58P₂O₅ glass was found to have the highest chemical stability among the studied NFP samples; the influence of TiO₂, ZrO₂ on crystallization in this composition was studied. It is found that addition of 3.4 mol% TiO₂ or 2.2 mol% ZrO₂ had little effect on the crystallization behavior of this glass. However, when the amounts of TiO₂ or ZrO₂ were increased to 8.4 or 5.5 mol% respectively the glass readily devitrified. Furthermore the addition of fluorine (introduced by replacing Na₂CO₃ with NaF in the glass batch) leads to amorphous glasses which could be crystallized to form NaFeP₂O₇ upon controlled thermal treatment. With increasing NaF additions the activation emergy for crystallization decreased from 428 to 381 kJ/mol.     

GeS2-Sb2S3玻璃的三阶非线性研究

采用熔融-急冷法制备了(100-x)GeS2-xSb2S3(x=10%、15%和20%)系列硫系玻璃,测试了样品的折射率、从可见到近红外的透过特性.采用Z-扫描方法测试了样品的三阶非线性特性,分析了Sb2S3的含量对玻璃的线性折射率,透过率和三阶非线性性能的影响.结果表明样品的线性折射率、非线性折射率n2、非线性吸收系数β以及三阶非线性光学极化率χ(3)随着Sb2S3的含量增加而增大,Sb2S3物质的量含量为20%的样品在800 nm处的三阶非线性折射率n2和非线性吸收系数β分别为:n2=3.27×10-10 esu和β= 31.5 cm/Gw.     

Study of Lanthanum Aluminum Silicate Glasses for Passive and Active Optical Fibers

We are reporting on SiO₂-Al₂O₃-La₂O₃ glasses—with and without Yb₂O₃—suitable for nonlinear and fiber laser applications. We will also be presenting successful supercontinuum generation and fiber laser operation around 1060 nm in step-index fibers. We optimized the glass compositions in terms of thermal and optical requirements for both a high La₂O₃ and Yb₂O₃ concentration and good compatibility with a silica cladding. We also produced bulk samples, unstructured fibers, and structured fibers with a SiO₂-Al₂O₃-La₂O₃ core and silica cladding for this purpose.     

Photoluminescence Properties of Zinc Oxide in Barium and Fluorine Silicate Glasses

Zinc oxide (ZnO) was embedded in barium and fluorine silicate glass matrices, and luminescence properties of as-prepared glass samples were studied. For the fluorine-free glasses, a blue emission was observed. With partial substitution of BaF₂ for BaO in glass compositions, emission spectra of glasses show an obvious blue shift to the near-UV region. For the BaO-free glasses, the dominant UV emission shifts to the near-band-edge exciton emission position of ZnO and also shows a red shift with increasing BaF₂. At the same time, a visible emission shoulder appears in the blue to green region and becomes weak with introduction of increasing BaF₂.     

Physical Properties and Structure of Silicate Glasses: I, Additive Relations in Alkali Binary Glasses

Correlations between certain physical properties, P , and all eighteen compositional ratios between the five ionic parameters of the system were studied with a computer for the five alkali silicates. Linear relations were found between P and the alkali/silica, alkali/oxygen, and silica/alkali ratios for certain regions of the glass field when the P's are expressed in proper molar terms. Specific volume and heat of formation data indicate three linear regions with two sharp break points between. The log electrical resistivity and the volatilization loss show two such regions and only the second break point. The break points, while structural in origin, must therefore occur for different reasons. The break points are the same for all P's and coincide with the eutectics. The constants of the linear relations are the partial molar quantities associated with P. Break points are not found in the molar refractivity data, so that no change in ligancy for these systems is indicated.     

Influence of Intermediate ZnO on the Crystallization of PbSe Quantum Dots in Silicate Glasses

Glasses containing PbSe quantum dots have important prospective applications in the area of near infrared optoelectronic devices. ZnO plays an important but complicated role in the preparation of quantum dot glass. We gave reasonable elaborations on the color changes of the as‐prepared and annealed glasses containing PbSe quantum dots. The as‐prepared glasses presenting nearly black to transparent straw‐yellow colors with rising ZnO content can be understood in terms of the conversion between PbSe and ZnSe; the colors of all annealed glasses turning very black can be well explained through thermodynamic calculations with the Gibbs–Helmho1tz equation. Next, according to the results of X‐ray diffraction, transmission electron microscopy and optical measurements, the sample with an introduction of 9.4 wt.% ZnO possesses a maximum degree of crystallization and the best optical properties among all samples, which suggests the host glass with addition of 9.4 ± 1 wt.% ZnO is optimum for crystallization of PbSe quantum dots. Finally, we employed classical nucleation theory to quantitatively calculate the nucleation rates and growth rates of PbSe quantum dots, and found that with the growing ZnO content in host glass, the nucleation rate decreases, whereas the growth rate of PbSe quantum dot increases gradually.     

Preparation and Properties of Oxynitride Glasses Made from Potassium Metaphosphate

Potassium phosphate oxynitride (KPON) glasses were made by heating crystalline KPO₃ at 702^° to 775^°C in dry ammonia. The softening temperature, thermal expansion coefficient, refractive index, and dissolution rate in water were measured as a function of nitrogen content and compared with the properties of oxynitride glasses made from LiPO₃ and NaPO₃.