Bismuth-containing fluoride glasses

The example of bismuth-containing glasses based on InF₃ and ZrF₄ is used to consider the effect of bismuth on glass formation, properties, and structure and the appearance of broadband luminescence at low wavelengths in the IR spectra of fluorozirconate glasses.     

Preparation of high-purity Fluorozirconate Glasses

The properties of glasses of quaternary and quinary systems synthesized on the basis of zirconium fluoride are shown. In particular, the influence of impurities, phase inhomogeneities, and gaseous bubbles on their optical properties are discussed. Methods for the preparation and characterization of high-purity fluorozirconate glasses as quinary systems are reported.     

Relationship between the energy characteristics of formation of fluorozirconates

A correlation is established between the mean energy of fluorine addition in a particular coordination polyhedron and the fluorine content in fluorozirconates by quantum chemical model cluster calculations and analysis of structural data for crystalline fluorozirconates. A new energy approach to studies of complex fluorides is suggested. It is shown that the mean energy of fluorine addition varies within a narrow range for any structural unit met in real fluorozirconate crystals. Based on the energy approach to analysis of vibrational spectra it is found that the coordination number of zirconium in a series of barium fluorozirconate glasses is 7 or 8. Translated fromZhurnal Strukturmoi Khimii, Vol. 41, No. 2, pp. 255–262. March–April, 2000.     

Vibrational Spectroscopy Study of Fluorozirconate Glasses Containing Tin Difluoride and Gallium Trifluoride

A series of fluorozirconate glasses in ZrF₄-SnF₂-GaF₃ and ZrF₄-SnF₂-BaF₂ systems have been studied by vibrational spectroscopy. The glass net contains not only fluorozirconate polyhedra, but also fluorostannate and fluorogallate groups. When contained in amounts of more than 10 mol.% in a glass, tin difluoride is a glass-forming agent. Gallium trifluoride in the same amount or higher forms GaF₆ polyhedra.     

The comparison of calculated transition probabilities with luminescence characteristics of erbium(III) in fluoride glasses and in the mixed yttrium-zirconium oxide crystal

Fluorozirconate glasses containing 2 mole% ErF₃ were prepared by melting the binary fluorides with ammonium bifluoride under an atmosphere of carbon tetrachloride and argon at 850°C. Absorption spectra of these glasses were obtained and the Judd-Ofelt parameters were calculated. Emission spectra and lifetimes of erbium in fluorozirconate glass, in lead-gallium-zinc fluoride glass, and in yttrium-zirconium oxide crystal were measured and compared with the theoretical calculations. Laser emission lines in these materials are deduced from these measurements. It is suggested that materials doped with erbium may serve as light sources for fiber optic waveguides made from the undoped materials.     

Influence of thermal stability on dielectric properties of SiO<Subscript>2</Subscript>–K<Subscript>2</Subscript>O–CaO–MgO glasses

Compositions of 55SiO₂–10K₂O–(35–x)CaO–xMgO are prepared by melt and quench technique. Thermal parameters of the as-prepared glasses are studied using the differential thermal analyzer under non-isothermal conditions. Kissinger, Augis–Bennett and Lasocka models are employed to investigate the kinetics of crystallization and thermal stability of these glasses. Based on this, it is concluded that CM-15 glass exhibits highest thermal stability. Raman spectroscopy is used to reveal the structural units of the glasses. Dielectric properties are observed through impedance spectroscopy. All the glasses are phase separated. The ratio of CaO/MgO influences the thermal stability, which leads to affect the dielectric properties. The highest dielectric permittivity is observed ~22 at room temperature and 100 Hz for CM-15 glass, where CaO/MgO ratio is ~1.33.     

Evaluation of the stability of substituted InF3 glasses by differential thermal analysis

The thermal properties and devitrification behaviour of substituted InF₃ glasses were studied by means of differential thermal analysis. A comparison of various simple quantitative methods to assess the level of stability of multicomponent fluoride glass systems was also made. Most of these methods are based on critical temperatures. In this paper, a new parameter,k _d(T), is introduced to the stability criteria. The stabilities of several substituted InF₃ glasses were evaluated experimentally and correlated with the activation energies of crystallization via this new kinetic criterion and compared with those evaluated by other criteria.     

Determination of zirconium, barium, lanthanum, aluminium, sodium, hafnium and fluorine in fluorozirconate glasses

Summary A procedure is described for the determination of the cationic and anionic components in fluorozirconate glasses. Zirconium, barium, aluminium, lanthanum, sodium and hafnium were determined by inductively coupled plasma atomic emission spectrometry (ICP/AES) after dissolution of the sample with an acid mixture in a microwave oven. The fluorine content was evaluated with two different techniques, namely potentiometry with a fluoride ion-selective electrode (FISE) and ion chromatography (IC). In this case the sample was solubilized by fusion with sodium carbonate.     

Optical transitions of Mn2+ in fluoride glasses

The optical properties of Mn²⁺ ions have been extensively investigated in numerous host materials. The 3d⁵ electrons associated with the manganese ion are sensitive to crystal field and the optical transitions yield valuable information on the local environment. Thus, the Mn²⁺ ion optical spectra in fluorozirconate and fluorohafnate glasses suggest that these ions are in positions of low crystal field. Most likely Mn²⁺ substitutes for Ba²⁺ ions in these glasses. As the glass undergoes devitrification the Mn²⁺ ion spectrum changes suggesting that optical methods can be used for studying the temperature dependence of glass transitions.     

Thermodynamic, kinetic and electrical switching studies on Si15Te85−xInx glasses: Observation of Boolchand intermediate phase

An interesting topic for quite some time is an intermediate phase observed in chalcogenide glasses, which is related to network connectivity and rigidity. This phenomenon is exhibited by Si-Te-In glasses also. It has been addressed here by carrying out detailed thermal investigations by using Alternating Differential Scanning Calorimetry technique. An effort has also been made to determine the stability of these glasses using the data obtained from different thermodynamic quantities and crystallization kinetics of these glasses. Electrical switching behavior by recording I-V characteristics and variation of switching voltages with indium composition have been studied in these glasses for phase change memory applications.     

Thermal properties of oxide glasses

A criterion based on the length of induction period of crystallization was used to evaluate the thermal stability of M₂O·SiO₂ (M?=?Li, Na) glasses against crystallization. It was founded out that the stability of studied glasses against crystallization is Li₂O·SiO₂?<?Na₂O·SiO₂. The results coincide with the order determined by stability criteria based on temperatures and the values of activation energy. A criterion based on the length of induction period enables to discriminate among the thermal stabilities of the silicate glass systems.     

Influence of fluorine on thermal properties of lead oxyfluoride glass

Oxyfluoride glasses are the basic materials for obtaining transparent glass–ceramic (TGC) which can be used in a wide range of optoelectronics devices such as: amplifiers, up-conversion, telescopes, laser sources. Oxyfluoride TGC is obtained by the control heat treatment of the parent glass due to low phonon nanocrystalline phases. The oxyfluoride glasses from the sodium–lead–silica system were the object of investigation. The influence of fluoride content on the thermal properties of glasses was analyzed. Thermal characteristics of glasses like the transition temperature T _g, the temperature for the crystallization onset T _x, and the maximum crystallization temperature T _c, thermal stability parameter were determined by DTA/DSC method. The linear expansion coefficients of oxyfluoride glasses as a function of temperature were measured using a thermo-mechanical analyzer (TMA 7 Perkin-Elmer). The effect of crystallization on the thermal expansion coefficient and softening temperature T _s was found.     

Synthesis and Ion Mobility in Glasses of ZrF<Subscript>4</Subscript>–BiF<Subscript>3</Subscript>–Rb(Cs)F Fluoride Systems

A new procedure has been suggested for the synthesis of bismuth fluorozirconate glasses in the ZrF₄–BiF₃–MF systems (M = Rb, Cs), which is based on the use of the relatively moisture-resistant Rb₂ZrF₆ and Cs₂ZrF₆ fluorides rather than extremely hygroscopic rubidium and cesium fluorides. The types of ion motions, trends in ion mobility dynamics, and factors determining this dynamics as a function of the glass composition have been elucidated. A rather high ionic conductivity of glasses above 470 K, σ ≥ 10^–4 S/cm, makes them promising candidates for use in design of functional materials.     

Glass forming ability and thermal stability in the system ZrF46BaF26PrF3

New glasses have been synthesized in the system ZrF₄6BaF₂6PrF₃. Glasses were prepared by conventional fusion method and the vitreous domain was established. For vitreous samples the thermal stability parameters were determined, so that the best compositions could be selected according to a compromise between high glass forming ability and thermal stability vs. crystallization.     

Crystallization kinetic of fluoro- zirconate glasses by non-isothermal analysis

Fluoride glasses have been extensively studied due to their high transparency in the infrared wavelength. The crystallization kinetics of these systems has been studied using DTA and DSC techniques. Most of the experimental data is frequently investigated in terms of the Johnson-Mehl-Avrami (JMA) model in order to obtain kinetic parameters. In this work, DSC technique has been used to study the crystallization of fluorozirconate glass under non-isothermal conditions. It was found that JMA model was not fit to be applied directly to these systems, therefore, the method proposed by Málek has been applied and the Šesták-Berggren (SB) model seems to be adequate to describe the crystallization process. This revised version was published online in July 2006 with corrections to the Cover Date.     

PMMA-ZrO2等有机无机杂化材料的制备与表征

以烯丙基乙酰丙酮作为偶闻剂应秀溶胶凝胶法制备了一系列均匀透明的ＰＭＭＡ－ＺｒＯ２等有机无机杂化材料，利用ＵＶ，ＩＲ对其制备过程进行了研究，并测定了所得杂化玻璃的ＴＧＡ性质。     

Excess entropy and thermal behavior of Cu- and Ti-doped bioactive glasses

Bioactive glasses belong to the ceramic family. They are good materials for implantation due to their excellent capacities to create an intimate bond with bones. Copper is known for its anti-inflammatory, antibacterial, and antifungal properties. Titanium is biocompatible and resistant to corrosion. These chemical elements can be introduced in bioactive glasses to provide a wide variety of uses and to enhance the physiological properties of implanted biomaterials. In this work, bioactive glasses doped with different contents of copper and titanium were synthesized by the melting method. The purpose is to study the effect of doping metal element on the thermal characteristics (T _g, T _c, and T _f). The results revealed that the increase of the content of copper and titanium in the glass matrix decreases the melting temperature and induces an increase of the thermal stability. The excess entropies of pure and doped glasses were calculated. Obtained results highlighted the decrease of the excess entropy with the increase of metal elements contents.     

Investigation of thermal stability and spectroscopic properties in Er3+/Yb3+-codoped TeO2-Li2O-B2O3-GeO2 glasses

The new Er3+/Yb3+ co-doped 70TeO2-5Li2O-(25-x)B2O3-xGeO2 (x = 0, 5, 10, 15 fand 20 mol.%) glasses were prepared. The thermal stability, absorption spectra, emission spectra and lifetime of the 4I(13/2) level of Er3+ ions were measured and studied. The FT-IR spectra were carried out in order to investigate the structure of local arrangements in glasses. It is found that the thermal stability, absorption cross-section of Yb3+, emission intensity and lifetime of the 4I(13/2) level of Er3+ increase with increasing GeO2 content in the glass composition, while the fluorescence width at half maximum (FWHM) at 1.5 um of Er3+ is about 70 nm. The obtained data suggest that this system glass can be used as a candidate host material for potential broadband optical amplifiers.     

Nd3+/Yb3+离子共掺的氧化钛基上转换发光玻璃的热学和力学性能

利用气悬浮无容器技术制备出了Nd³⁺/Yb³⁺稀土离子共掺杂的TiO₂-La₂O₃-ZrO₂(TLZ)发光玻璃. 利用差热分析(DTA)技术研究了该类新型稀土掺杂TiO₂基上转换发光玻璃的热稳定性,主要包括玻璃化转变温度、析晶起始温度以及析晶峰值温度. 并采用两种热分析动力学计算方法得到TLZ玻璃的析晶活化能值和指前因子.本文还研究了TLZ 发光玻璃的力学性能,发现其维氏硬度大小为7.50 GPa,断裂韧性大于1.20 MPa·m^1/2. 此外,还对TLZ玻璃在808 nm激光激发下的上转换发光性能进行了研究,实验结果显示光谱中有三个强发射谱峰. 优异的上转换发光性能以及良好的热稳定性和机械性能表明,这类新材料在上转换器件的实际应用中具有很大的潜力.     

Thermal properties of oxide

To evaluate the thermal stability of oxide glasses, various criteria have been used. Not only the simple parameters, as characteristic temperatures and values of activation energy and enthalpy changes, but also the combined criteria E/RTp and kf(T) have been taken into account. Three glasses with the composition of Li₂O·2SiO₂ (a), Li₂O_·2SiO₂·0.03TiO₂ (b) and Li₂O·2SiO₂·0.1TiO₂ (c) were prepared and the validity of the criteria was tested by applying them to these glasses. The results indicate that the sequence thermal stability of the studied glass system vs. crystallization depends not only on their composition but also on the used criteria. This revised version was published online in August 2006 with corrections to the Cover Date.