Near-IR luminescence from subvalent bismuth species in fluoride glass

The broadband NIR luminescence of subvalent bismuth species was demonstrated in partially reduced ZrF₄-BiF₃-NaF and ZrF₄-BiF₃-BaF₂ fluoride glasses. The parameters of luminescence were reported and compared with luminescence from other bismuth-doped materials. Since fluoride glass compositions are based on strong Lewis acids (ZrF₄ in present case) they can stabilize NIR photoluminescent subvalent bismuth species.     

Verres fluores dans le systeme ZrF4ThF4MF3 (M = Y,Lu, Sc,Al)

The glass forming area has been precised in the ZrF₄ThF₄YF₃ ternary system. It is smaller than in the ZrF₄ThF₃LaF₃ system and corresponds to the limits: 45–70 % ZrF₄, 30–50 % ThF₄, 0–12 % YF₃. A series of glass samples with molar composition 0.5 ZrF₄, 0.43 ThF₄, 0.07 MF₃ (M : La, Y, Lu, Sc, Al) has been prepared and the linear evolution of T_G, molar refractivity and anionic compactness versus the ionic radius of M³⁺ is shown. The thermomechanical properties are better than for previous fluorozirconate glasses including barium. The average values are 480° C for T_G, 580° C for T_C, 800° C for T_F, 1.54 for n_D, 90.10^?7 K^?1 for thermal expansion coefficient. The U.V. absorption edge is improved by comparison with standard ZrF₄ -and AlF₃- based glasses. The potential application to I.R. optical fibres is discussed.     

Glass formation in quaternary systems of group I-IV fluorides

We have studied the glass-forming regions in the lead-fluoride-containing quaternary fluorozirconate systems ZrF₄-PbF₂-LaF₃-NaF (ZPLN), ZrF₄-PbF₂-BaF₂-LaF₃(ZPBL), and ZrF₄-PbF₂-BaF₂-NaF (ZPBN). Their temperature characteristics have been determined by differential thermal analysis, and the most stable glass compositions have been identified.     

Glass Formation in the ZrF4–BaF2–AlF3–NaF, ZrF4–BaF2–LaF3–NaF, and ZrF4–BaF2–LaF3–AlF3 Systems

Data are presented on glass formation in the systems ZrF₄–BaF₂–AlF₃–NaF (25 mol % BaF₂ and 50, 53.5, 57, and 60 mol % ZrF₄), ZrF₄–BaF₂–LaF₃–NaF (25 mol % BaF₂), and ZrF₄–BaF₂–LaF₃–AlF₃ (25 mol % BaF₂). Differential thermal analysis results for the ZBLN, ZBLA, and ZBAN glasses were used to identify the most stable glass compositions.     

Phase relations in the PbF2-BaF2-ZrF4 system

We have investigated phase equilibria between PbZrF₆ and the barium fluorozirconates Ba₂ZrF₈, Ba₃Zr₂F₁₄, BaZrF₆, and BaZr₂F₁₀. The PbZrF₆-Ba₂ZrF₈ join has been shown to be pseudobinary, with simple eutectic phase relations. It defines the PbZrF₆-ZrF₄-Ba₂ZrF₈ compatibility triangle in the PbF₂-BaF₂-ZrF₄ system. Semicrystalline samples have been obtained at ZrF₄ contents in the range 40–70 mol %.     

Infrared transmitting glasses based on hafnium fluoride

The synthesis and properties of glasses in the systems HfF₄/1bBaF₂/1bThF₄, HfF₄/1bZrF₄/1bBaF₂/1bThF₄ and HfF₄/1bBaF₂/1bLaF₃ are reported. The glasses have higher densities and better glass formation tendencies than those in which ZrF₄ is the major network forming constituent. Optical measurements indicate that the HfF₄ based glasses transmit longer wavelengths in the IR than ZrF₄ based glasses. It is suggested that any increase in scattering loss in going from ZrF₄ to HfF₄ will be offset by the lower multiphonon losses in the latter.     

Verres fluores paramagnetiques a base de Eu++

Glass formation has been studied in the ZrF₄EuF₂CeF₃ ternary system. Although these glasses show higher devitrification tendency than standard fluorozirconate glasses containing BaF₂, stable samples could be prepared from the ZEC-8 composition 0.55 ZrF₄, 0.36 EuF₂, 0.08 CeF₃, 0.006 AlF₃, 0.004 CaF₂. Characteristic temperatures Tg, Tx and Tm are 328, 394 and 630° C respectively. The value of refractive index is n_D = 1.5535. Magnetic measurements show that a part of europium has a 3 oxidation state. Glass structure and atomic coordinations are discussed by comparison with ZrF₄BaF₂ glass.     

The recrystallization of ZrF4 and AlF3

A recrystallization method which yields large crystals of ZrF₄ and AlF₃ is described. The recrystallization of ZrF₄ and AlF₃ at 650°C and 1100°C, respectively, provides large, clear and transparent, centimeter size samples. Both compounds readily sublime without melting; thus they are not amenable to crystal growth methods from the melt such as Czochralski or Bridgman.     

Nouveaux verres au tetrafluorure de zirconium ne contenant pas d'element modifieur

Vitreous phases are investigated in the ZrF₄-ThF₄-NdF₃ and LaF₃ ternary systems. Binary glass Zr_1?xTh_xF₄ have been obtained. A typical composition in the glassy area is 0,6 ZrF₄, 0,3 ThF₄, 0,1 LnF₃. The characteristic temperatures are higher than previously measured for zirconium fluoride glasses. Optical transmission range lies from 0,22 to 7μ. The structure is described as an infinite framework built from MF₇, MF₈ and MF₉ polyhedra. In theses glasses, ZrF₄ acts as network former, ThF₄, LaF₃ and NdF₃ as network stabilizers. Absence of network modifier (BaF₂) explains the physical properties evolution.     

Fluoride bridging modes in fluorozirconate glasses by x-ray and computer simulation studies

A second characteristic ZrZr distance due to edge-sharing (ZrF_n) polyhedra which is observed in crystalline α-ZrF₄ (high temperature form) and is also suggested by recent X-ray studies of BaF₂ZrF₄ glasses, has been observed in ion dynamics computer simulation studies. Experimental X-ray and computer simulation results both imply that about one out of each four bridges between Zr pairs involve two fluoride ions, and that this proportion is almost independent of composition in the binary system.     

Preparation of High-Purity ZrF4and HfF4for Optical Fibers and Radiation-Resistant Glasses

The separation coefficients of ZrF₄(HfF₄) and metal fluoride impurities in the process of vacuum sublimation between 900 and 1200 K in the molecular vaporization regime were calculated. The separation coefficients were found to decrease in the order CrF₂> MnF₂> NiF₂> CoF₂> MnF₃> FeF₂> AlF₃> CrF₃> CuF₂> FeF₃. The conditions for purification of ZrF₄and HfF₄by vacuum sublimation were optimized. The total impurity content in both fluorides was found to increase with the product of the evaporation rate per unit area and the degree of evaporation. Fe was found to be the most difficult-to-remove impurity in ZrF₄and HfF₄. The production rate of the sublimating plant is about 100 kg/year of ZrF₄and HfF₄sublimates. ZrF₄was used to prepare optical fibers for laser applications and noncontact fiber sensors for monitoring the composition and temperature of liquid radioactive waste. Fluorohafnate glasses were used to fabricate radiation-resistant scintillating modules of dimensions 20 × 30 × 150 mm, weighing 0.5 kg.     

Glass Formation in the ZrF4–BaF2–LaF3–AlF3–NaF System

Glass formation in the ZrF₄–BaF₂–LaF₃–AlF₃–NaF system is studied by differential thermal analysis at fixed ZrF₄ (50–60 mol %) and BaF₂ (20–30 mol %) contents. Using stability criteria, the most stable glass compositions are identified.     

Effect of addition of chloride on the crystallization behaviour of fluoride glasses in ZrF4-BaF2-CsF system

Fluoride glasses based on ZrF₄-BaF₂-CsF doped with BaCl₂ up to 10 mol% have been prepared. Crystallization behaviour of these glasses has been investigated by means of DTA and XRD. Addition of 5 mol% BaCl₂ into the fluoride glass of the ZrF₄-BaF₂-CsF system enhances the glass forming ability and the thermal stability against crystallization, but the glass forming ability is decreased for glass containing 10 mol % of BaCl₂. The results have been discussed from the view point of thermodynamics and the dynamics of glass formation.     

Phase Relations in the PbF2–LaF3–ZrF4 System

The phase relations in the PbF₂–LaF₃–ZrF₄ system are studied along the LaZrF₇–PbZrF₆ and LaZr₂F₁₁–PbZrF₆ joins and at fixed ZrF₄ contents of 35, 60, 65, and 70 mol %. The primary phase fields and invariant points are located.     

Influence of processing conditions on IR edge absorption in fluorohafnate and fluorozirconate glasses

The influence of processing conditions on the IR absorption edge of fluoride glasses with the composition 62 MF4 1b 33 BaF₂ 1b 5 LaF₃ (M = Hf or Zr) is reported. At higher values of the absorption coefficient (α > 1 cm^?1), the IR edge is nearly independent of processing conditions and appears to be intrinsic. At lower values (α < 1cm^?1) extrinsic features attributed to oxide impurities appear; these are suppressed when glass melting is carried out in a reactive atmosphere of CCl₄. Comparison of our results for HfF₄- and ZrF₄ based glasses shows that substitution of HfF₄ for ZrF₄ shifts the IR edge to longer wavelengths, but the intrinsic absorption curves are nearly parallel over the frequency range investigated.     

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.     

Anion conduction in fluorozirconate glasses

Fluorozirconate glasses have been prepared and their ionic conductivity measured as a function of composition and temperature. All compositions are good fluoride ion conductors with conductivities at 250°C in the 10^?6–10^?5 (Ω-cm)^?1 range and activation energies between 0.7 and 0.9 eV. The fluoride ion to metal ratio was varied in the ZrF₄/1bBaF₂/1bThF₄/1bNaF system by replacing ZrF₄and/or BaF₂ with NaF. When Na⁺ substitutes for Ba⁺² a systematic decrease in the conductivity, σ, and the activation energy, E_a, is seen. This is explained on the basis of a reduction of carriers and on the modification of the network by Na⁺ ions. No systematic variation in σ or E_a were seen when Na⁺ replaces Zr⁺⁴. A change in slope of the log σ vs 1/T plot was seen at the glass transition temperature in La-containing glasses.     

含ZrF4氟铝酸盐玻璃研究

以10MgF2-20CaF2-10SrF2-10BaF2-15YF3-35A1F3(摩尔百分数）氟铝酸盐玻璃为基本组成，在玻璃中引入不同含量的ZrF4，同时对其它组成进行适当调整，制得了厚度8mm无可见析晶的氟化物玻璃．利用差热分析(DTA)技术研究了ZrF4对玻璃形成能力和玻璃析晶动力学的影响，结果表明，少量的ZrF4可以提高玻璃的抗失透能力，过量的ZrF4会降低玻璃形成能力；ZrF4的最佳含量范围为7．3-11．4mol％．根据测得的玻璃的红外透过光谱显示，该玻璃具有良好的透红外光性能．     

Nouveaux verres fluores

New fluoride glasses have been obtained in the ZrF₄ThF₄BaF₂ systems. Large samples have been prepared in order to determine some physical properties. Optical transmission range lies from 0,22 to 7μ, the refractive index is about 1, 53 and can be modulated by chemical composition. Glass temperature, crystallization and melting temperature have been measured.     

Mixed alkali effect in elastic properties of glasses in the ZrF4-BaF2- AlF3-RF system (RF = LiF-NaF,NaF-KF)

The elastic properties, such as Poisson's ratios, shear modulus, Young's modulus and bulk modulus, have been determined with glasses of the compositions 48ZrF₄ · 24BaF₂ · 8AlF₃ · 20RF, where RF is the LiF-NaF or NaF-KF pair, and 42ZrF₄ · 21BaFe₂· 7AIF₃ · 30RF, where RF is the LiF-NaF pair, by measuring sound wave velocities. Non-linear variations, i.e. mixed alkali elects, were found in the sound velocities, shear modulus, Young's modulus and bulk modulus. The mixed alkali effect in the present systems is attributed to the strengthening of the glass structure and not to the mere compaction of the glass structure. The thermal expansion coefficient becomes higher when the two alkalis are mixed contrary to expectation from the change of the elastic moduli, indicating that the structural elements controlling the elastic moduli re different from those affecting the thermal expansion.