Cadmium halide glasses. II. - Chloride glasses

New chloride glasses based on CdCl₂ have been discovered in the binary composition (Cd_0.5Ba_0.5)Cl₂ and in the two ternary systems CdCl₂-BaCl₂-KCl and CdCl₂-BaCl₂-NaCl within the limits in mole percent: 30–60 CdCl₂, 15–50 BaCl₂, 0–35 KCl or NaCl. Other chlorides such as LiCl, CsCl₂, ZnCl₂, PbCl₂, SrCl₂, AgCl may be included in the glass composition. Only thin samples may be obtained by quenching the melt. Although less hygroscopic than ZnCl₂ glasses, they undergo a surface attack by atmospheric water. For a representative glass Cd_0.5Ba_0.3K_0.2Cl_1.8, glassy transition occurs at 167° C, crystallization at 221 and melting at 363° C. Their optical transmission range lies continuously from the U.V.-visible spectrum to 16 μ in I.R. region. They appear thus as attractive new materials for infrared technology at 10.6 μ and for low-loss optical fibres. The structural discussion is based on the assumption of the 6-coordination of cadmium.     

Preparation and properties of fluorozirconate glasses containing divalent europium

The glass forming region of the (ZrF₄BaF₂ThF₄)EuF₂ system has been studied. EuF₂ was found to replace up to about 85% of the BaF₂ in a glass with a composition .615 ZrF₄, .32BaF₂, .07ThF₄. The glass transition temperature is seen to increase with the EuF₂ concentration. The 4f⁷→ 4f⁶5d¹ transition of the Eu⁺² ion in the glass matrix was studied by optical absorption and compared with data taken on crystalline compounds containing Eu⁺² in different environments. It is concluded from these results that the Eu⁺² ion - and also the Ba⁺² ion - is coordinated by 12 fluorides in the glass.     

X-ray diffraction studies of phase transformations in heavy-metal fluoride glasses

The crystallization of five ZrF₄-based glasses has been investigated using powder X-ray diffraction and differential scanning calorimetry. The crystalline phase in Zr-Ba-La-Pb fluoride glass was found to be-BaZrF₆. In other glasses the crystal phases could not be identified. Reversible polymorphic phase transformations occur in Zr-Ba-La-Li and Zr-Ba-La-Na fluoride glasses when heated to higher temperatures.     

硼铝酸锶长余辉发光玻璃的制备及发光性能研究

采用一步合成法制备了硼铝酸锶长余辉发光玻璃,系统研究了热处理温度、热处理时间、冷却制度等条件对长余辉玻璃发光性能的影响.结果表明:在N2气氛下,热处理温度为1300℃、保温时间为3h、试样随炉冷却的制备工艺可得到发光性能优良的长余辉玻璃,该玻璃的长余辉特性源自在玻璃基体中均匀分布的Eu2 、Dy3 共掺杂的SrAl2O4微晶.     

Preparation method and thermal properties of samarium and europium-doped alumino-phosphate glasses

The present work investigates alumino-phosphate glasses from Li₂O–BaO–Al₂O₃–La₂O₃–P₂O₅ system containing Sm³⁺ and Eu³⁺ ions, prepared by two different ways: a wet raw materials mixing route followed by evaporation and melt-quenching, and by remelting of shards. The linear thermal expansion coefficient measured by dilatometry is identical for both rare-earth-doped phosphate glasses. Comparatively to undoped phosphate glass the linear thermal expansion coefficient increases with 2 × 10⁻⁷ K⁻¹ when dopants are added. The characteristic temperatures very slowly decrease but can be considered constant with atomic weight, atomic number and f electrons number of the doping ions in the case of T_g (vitreous transition temperature) and T_sr (high annealing temperature) but slowly increase in the case of T_ir (low annealing temperature–strain point) and very slowly increase, being practically constant in the case of T_D (dilatometric softening temperature). Comparatively to undoped phosphate glass the characteristic temperatures of Sm and Eu-doped glasses present lower values. The higher values of electrical conductance for both doped glasses, comparatively to usual soda-lime-silicate glass, indicate a slightly reduced stability against water. The viscosity measurements, showed a quasi-linear variation with temperature the mean square deviation (R²) being ranged between 0.872% and 0.996%. The viscosity of doped glasses comparatively to the undoped one is lower at the same temperature. Thermogravimetric analysis did not show notable mass change for any of doped samples. DSC curves for both rare-earth-doped phosphate glasses, as bulk and powdered samples, showed T_g values in the range 435–450 °C. Bulk samples exhibited a very weak exothermic peak at about 685 °C, while powdered samples showed two weak exothermic peaks at about 555 °C and 685 °C due to devitrification of the glasses. Using designed melting and annealing programs, the doped glasses were improved regarding bubbles and cords content and strain elimination.     

Inorganic chloride and mixed halide glasses with low maximum phonon frequencies

A class of inorganic chloride glasses based on BiCl₃ as glass-former is described, and their glass transition temperatures reported. They are characterized by infra-red transparency to unusually long wavelengths.     

Effect of pressure on the resistivity of lead oxide-lead halide glasses

Resistivity behaviour of PbOPbX₂ (X=F,Cl) glasses has been investigated as a function of pressure at laboratory temperature. All PbOPbX₂ glasses undergo crystallization under pressure and the resistivities of crystallized samples are lower than the corresponding glasses. Transitions in PbOPbF₂ glasses exhibit a first order behaviour while transitions in PbOPbCl₂ glasses possess features of a continuous transition. The differences in the pressure behaviour of the two glass systems have been attributed to the differences in the ionic sizes of F^? and Cl^? ions and also to pressure induced modifications of PbO bonding.     

Preparation of meter-long alkali halide single crystals

High purity single crystals of LiF, NaF, and KCl have been produced exceeding 1 meter in length and having a nearly uniform diameter of approximately 1 cm. The Czochralski seed-pulling technique was used in conjunction with apparatus constructed at Cornell University.     

Preparation and properties of rapidly quenched glasses in the V2O5-PbO system

Rapidly quenched glassy films in the V₂O₅-PbO system were prepared using a twin-roller type apparatus. The glass formation region was 0–60 mol% PbO. The first crystallization temperature increased from 210 C for the V₂O₅ glass to 292 C for the glass of 60 mol% PbO. The metastable unknown phase was first crystallized in the glasses around 50 mol% PbO. Infrared absorption spectra of the glasses were measured. Electrical conductivity of the glasses decreased with increasing of PbO content. The electrical behaviour of the glasses is discussed based on the glass structure estimated from the infrared spectral data.     

Electrical properties of barium-borosilicate glasses

Bulk and thin-blown films of barium-borosilicate glass were prepared and their electrical conduction properties at high and low fields were measured as functions of temperature. The electrical conductivity is an exponential function of inverse temperature at high temperatures with an activation energy in the range 1.0 to 1.4 eV, depending on composition. The conduction process is believed to involve polarons hopping in the adiabatic regime. Some high-field electroforming effects are observed.     

Viscosity properties of tellurite-based glasses

The viscosity behavior of glasses with the composition (90-x)TeO₂-10Bi₂O₃-xZnO with x = 15, 17.5, and 20 (TBZ glasses) and 80TeO₂-(20-y)Na₂O-yZnO system with y = 0, 5, and 10 (TNZ glasses) have been measured as a function of temperature using a beam-bending (BBV) and a parallel-plate (PPV) viscometer. The structure of the glass’ network has been characterized using Raman spectroscopy and has been related to the viscosity temperature behavior and the fragility parameter (m) of the glasses. As the concentration of ZnO in the TBZ system (x) increases, the fragility parameter of the glass increases, whereas it decreases with an increase of the ZnO concentration (y) in the TNZ system. In both glasses, these variations in m have been related to the partial depolymerization of the tellurite network associated with the level of modifier content. The depolymerization of the tellurite network is believed to be the result of a reduction in the number of [TeO₄] units and the formation of [TeO₃] and [TeO₃₊₁] units that occurs with a change in TeO₂ content in the TBZ system and modifier content in the TNZ system.     

Elastic properties of As-Sb-Se glasses

Results of measurement of elastic modulii on As-Sb-Se glasses are reported and their composition dependence discussed. The Young’s and the shear modulii lie in the range of 170–210 and 65–80 kb respectively. These values are typical of chalcogenide glasses. For (As, Sb)₄₀Se₆₀ glasses, the modulii increase monotonically with increasing Sb₂Se₃ content. The observed composition dependence of the modulii for the As _x Sb₁₅Se_{85 −x} glasses is examined in terms of the chemically ordered structural units in the glasses.     

Elastic properties of phosphotungstate glasses

Elastic properties of potassium and lead phosphotungstate glasses have been investigated using ultrasonic velocity measurements. The composition dependence of elastic moduli in WO₃-K₂O-P₂O₅ glasses suggests that at low alkali oxide concentrations the atomic ring size increases by network modification, which results in the decrease of elastic moduli. In the highly modified regime, due to the presence of coulombic interaction, the rate of decrease of elastic moduli is reduced. In the WO₃-PbO-P₂O₅ glasses the behaviour of elastic moduli suggests that PbO behaves both as a network former and network modifier. The incorporation of PbO into the network is quantitatively determined by the concentration of P₂O₅ in the system. The results are consistent with the structural model proposed earlier, based on characterization studies.     

Mid-infrared luminescence properties of Dy-doped silver halide crystals

The absorption and the kinetics of the emission in the mid-infrared (mid-IR) were investigated in AgCl(x)Br(1-x) crystals doped with Dy(3+) ions. Strong emission bands were detected at 3, 4.4, and 5.5 μm and attributed to the (6)H(13/2)→(6)H(15/2), (6)H(11/2)→(6)H(13/2), and (6)F(11/2)+(6)H(9/2)→(6)H(11/2) transitions. Various optical parameters were calculated for the Dy(3+) doped crystals, using the Judd-Ofelt approximation and the rate equations. The measured results and the calculated parameters indicate that these doped crystals could be used for the development of mid-IR solid-state lasers or mid-IR fiber lasers.     

Luminescent and thermo-optical properties of germanate glasses

The visible photoluminescence of Tb³⁺-doped germanate glass of composition (in mol%) 40GeO₂–20Na₂O–40SiO₂ has been investigated for two Tb³⁺ concentrations. By using steady-state and pulsed laser spectroscopy. Concentration effects on luminescence are observed for Tb³⁺ concentration higher than 0.9 mol%. The thermo-optical characteristics were measured at room temperature under resonant conditions on the Tb³ ions. The thermo-optical properties of the glasses showed a dependence on the concentration of terbium ions. The effects of TL were also analyzed in terms of a theoretical model for CW laser induced thermal lensing under a Gaussian-beam approximation. Tb³⁺ concentration quenching effects on the dependence of thermo-optical properties are discussed.