Verres fluores a large bande de transmission optique et a haute resistance chimique

New stable fluoride glasses have been obtained in the ThF₄-AlF₃-YF₃-BaF₂ quaternary system. The vitreous areas are described in the ThF₄-(Al_0.5Y_0.5)F₃-BaF₂ system and in the four basic ternary diagrams. For a standard glass with molar composition 22.5 % ThF₄, 28.75 % AlF₃, 28.75 % YF₃, 20 % BaF₂, the characteristic temperatures are 446° C for T_G and 710° C for the fusion. The refractive index n_D is 1.489 and the density is 5.1. The optical transmission range lies from 330 nm to 7000 nm. These glasses are fluorine and water resistant. They are potential ultralow-loss optical fiber materials. Glass formation in this system is discussed by reference to the ionic analysis of the vitreous state.     

Verres au fluorure de scandium

New fluoride glasses deriving from ScF₃ as glass progenitor have been investigated. The best ternary compositions have been obtained within the ScF₃YF₃BaF₂ ternary system for molar compositions: 0.3–0.6 ScF₃, 0.05–0.25 YF₃, 0.35–0.50 BaF₂. For the standard SYB-4 glass (Sc₀₄Y_0.2 Ba_0.4)F_2.6, the glassy transition occurs at 360° C, melting at 720° C and two crystallization stages at 410° C and 485° C. Other physical values are 1.4985 for refractive index n_D, 4.38 for density, 180. 10^?7 K^?1 for thermal expansion coefficient. Vitreous areas have been investigated in the ScF₃BaF₂ThF₄, ScF₃BaF₂NaF, ScF₃ThF₄YF₃ and ScF₃YF₃BaF₂NaF systems. Most fluoroscandate glasses are water resistant and are continuously transparent from 300 nm in U.V. spectrum to 7000 nm in I.R. spectrum, with a classical OH band around 3000 nm, and are suitable for I.R. transmittance or medium I.R. optical fibres. Glass formation in these systems is discussed by reference to an ionic model.     

Etude des verres fluores dans les quaternaires ZnF2ThF4AlF3MF2 (M = Mg,Ca, Sr,Ba)

Fluoride glasses have been investigated in the ZnF₂AlF₃ThF₄MF₂ (M = Ba, Sr, Ca, Mg) systems. The vitreous areas are given for the basic ternary diagrams and at a constant 40 % ZnF₂ content. Small samples may be prepared for the compositions: 40 % ZnF₂, 20 % AlF₃, 20 % ThF₄, 20 % MF₂ (M = Ba, Sr, Ca). The glassy transition occurs between 310° C and 350° C and the fusion between 650° C and 750° C. The optical transmission range lies from 240 nm to 7500 nm. The average values of refractive index, thermal expansion coefficient and density are: n_D ～ 1.48, α ～ 15.10^?6° K^?1d ～ 5. The high compactness of the anion array is compared to that of close-packed crystalline fluorides.     

Verres aux halogenures de cadmium : I.- Verres fluores

New halide glasses based on cadmium halides as glass progenitors have been discovered. This paper describes fluoride glasses in the CdF₂-BaF₂-ZnF₂ ternary system. Binary glasses Cd_xBa_1?xF₂ (0.45 < x < 0.52) have been obtained. The limits of the glassy area are: 5–55 % CdF₂, 15–55 % BaF₂, 0–60 % ZnF₂. Numerous fluorides such as the alkali fluorides, AlF₃, YbF₃ and ThF₄ may be included in the glass composition. Only thin glass samples may be prepared because of the high crystallization rate. The characteristic temperatures of the Cd_0.3Ba_0.4Zn_0.3F₂ glass are 290° C for T_G, 330° C for T_C and 620° C for T_F. The optical transmission spectrum of a thin sample shows an extrinsic absorption band at around 9000 nm and the multiphonon IR absorption edge beyond 10500 nm. The optimization of these glasses will make them attractive materials for IR transmittance and IR optical fibres. The crystallization of the Cd_0.5Ba_0.5F₂ glass results in two solid solutions Ba_1?xCd_xF₂ and Cd_1?xBa_xF₂ deriving from the fluorite structural type. Thus, cadmium fluoride glasses appear as the result of the disordering of the fluorite type structure in the same way as ZrF₄-based glasses derive from the disordering of the ReO₃-type structure. Both glasses may be described as the random insertion of cations into an aperiodic array of F^? anions.     

Solubility of UF4, ThF4, and CeF3 in the NaF-ZrF4 melt

The solubility of UF₄, ThF₄, and CeF₃ in a fluoride melt 52 mol % NaF-48 mol % ZrF₄ in the temperature range 550–750°C was studied. The solubility of the fluorides in the melt increases with temperature. At 600°C and higher temperatures, the solubility decreases in the order UF₄ > ThF₄ > CeF₃. The temperature dependences of the solubility of UF₄, ThF₄, and CeF₃ in the NaF-ZrF₄ system are satisfactorily described by a linear equation.     

Etude de la conduction ionique de verres a base de ZrF4

The electrical and dielectric properties of new ZrF₄ based glasses have been studied in the frequency and temperature ranges 5Hz-500kHz and 130–280°C. Transport number measurements following Tubant's method showed that the glasses investigated are F^? conductors. The conductivities and activation energies for conduction are about 10^?6(Ωcm)^?1 at 200°C and 18 kcal.mole^?1 respectively. Preliminary interpretation of the change of conductivity with composition is given.     

Preparation of ZrF4-NaF-BaF2-LaF3-YbF2 glasses with YbF2 substitution for BaF2 (LaF3)

We have prepared glasses and semicrystalline phases with a green color in the systems ZrF₄(53.5)-NaF(20)-BaF₂(20)-LaF₃(6.5 ? x)-YbF₂(x) (0 ≤ x ≤ 6.5 mol %) (I) and ZrF₄(53.5)-NaF(20)-BaF₂(20 ? x)-LaF₃(6.5)-YbF₂(x) (0 ≤ x ≤ 20 mol %) (II). Thermal analysis results demonstrate that, in both systems, the glass transition temperature of the samples containing ≤3 mol % YbF₂ lies in the range 200–250°C, their heating curves show two or three crystallization events (at 320–340, 380–460, and 415–490°C), and their melting points range from 460 to 490°C. Increasing the YbF₂ content of the glasses to 4 mol % and above (system I) has no effect on their glass transition temperature, reduces the temperature of the first crystallization event from 340 to 305°C, and produces extra peaks in the range 545–600°C, above the major melting peak, which can be accounted for by a nonequilibrium state of the glasses. Ytterbium difluoride substitution for barium difluoride (10 to 20 mol %) (system II) leads to the formation of semicrystalline phases and increases the glass-transition (305°C), crystallization (470–515°C), and melting (570–690°C) temperatures. The IR spectra of such samples show, in addition to a so-called “featureless continuum” (～500 cm^?1), absorption bands characteristic of the Yb-F bond. Electronic spectra also confirm that the glasses contain both divalent and trivalent ytterbium.     

Composition dependence of infrared edge absorption in ZrF4 and HfF4 based glasses

A set of semi-empirical criteria have been developed to assess the contribution of various components to IR edge absorption in multi-component solids. These have been applied to ZrF₄ and HfF₄ based glasses and verified experimentally. Results indicate that monovalent cation fluorides no lighter than NaF, divalent cation fluorides no lighter than CaF₂, trivalent cation fluorides no lighter than LaF₃ and quadrivalent cation fluorides no lighter than ThF₄ contribute negligibly to IR edge absorption in such glasses.     

Une nouvelle famille de verres fluores transmetteurs dans l'infrarouge: Fluorures vitreux dans les systemes ThF4BaF2MF2 (M = Mn,Zn)

A new family of fluoride glasses based on ThF₄ has been isolated in the ternary systems ThF₄BaF₂MnF₂ and ThF₄BaF₂ZnF₂. These glasses have a good I.R. transmission: the absorption edge in the 9 μ region indicating that they are different from the ZrF₄ based glasses. To be stabilized, they must be quenched.     

IR transparency of the glass of ZnCl2-KBr-PbBr2 system

IR transparency and some properties of halide glass of composition 48ZnCl₂-48KBr-4PbBr₂ (mol%) have been investigated as the basic study on the development of IR glass fiber for CO₂ gas laser. The glass transition temperature Tg, crystallization temperature T_c, softning temperature T_s, and linear thermal expansion coefficient α of the glass were found to be 45–46°C, 100°C, 54°C, and 570×10^?7 / °C, respectively. The refractive index of the glass for He-Ne laser emission (632.8 nm) was about 1.63. The amount of impurity which decreases the transmissibility for CO₂ laser beam due to the absorption in the wavelength region 10–11 μm could be reduced by preparing the glass from a batch containing NH₄ Cl under reactive atmosphere of CCl₄ or CBr₄ in a glove box filled with He gas of dew point ?62～ ?45°C. The minimum value of absorption loss of the glass for CO₂ gas laser measured by laser calorimetry was about 20 dB/m.     

Determination du coefficient d'extinction molaire de OH− dans les verres fluores a base de metaux lourds

The extinction coefficient ? at 2.9 μm for OH in fluoride glasses is measured by determining the amount of HF evolved during heating of the glass under steam and the corresponding intensity of the OH absorption band. This coefficient is respectively equal to 31 litre mole^?1 cm^?1 for BTYbZ glass (15 BaF₂ - 29 ThF₄ - 28 YbF₃ - 28 ZnF₂) and 19.5 litre mole^?1 cm^?1 for BALLA glass (34 BaF₂ - 57 ZrF₄ - 4 AlF₃ - 5 LaF₃).     

Infrared-transparent glasses derived from the fluorides of zirconium,thorium, and barium

Glasses consisting solely of high-purity ZrF₄, ThF₄, and BaF₂ have been synthesized using reactive atmosphere processing (RAP) techniques. RAP of the individual components and the molten material with anhydrous HF and CCl₄ is described. The glass molds easily at 312°C and 1920 psi with a high-fidelity replication of the die surface. The glass is water insoluble, unusually hard and strong, and continuously transparent from 0.3 to 7 μm.     

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.     

Ionic conductivity of Li4GeO4, Li2GeO3 and Li2Ge7O15

The ionic conductivity of polycrystalline samples of three lithium germanates: Li₄GeO₄, Li₂GeO₃, and Li₂Ge₇O₁₅, has been determined using a c techniques and complex plane analysis. Conductivities at 400°C are 8.7 × 10^?5, 1.5 × 10^?5, and $\text{1.4 × 10}{}^{\mathrm{?7}}\text{(Ω·}\text{cm}\text{)}{}^{\mathrm{?1}}$ respectively. The conductivity of Li₄GeO₄ rises appreciably in the range 700–750°C.     

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．     

Fluoride glasses in the system ZrF4 BaF2 RF3 (R = Gd,Yb)

The synthesis and properties of fluoride glasses in the system ZrF₄BaF₂GdF₃ (or YbF₃) are reported. Addition of fluorides of other elements, such as AlF₃, PbF₂, LaF₃ improve glass formation and prevent crystallization. Optical measurements show that these glasses transmit wavelengths up to 8 μm. Doping with PbF₂ increases the refractive index from 1.513 to 1.536.     

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.     

Structure et conductivite electrique de verres appartenant au systeme Li2Si2O5 Li2SO4

The conductivity of vitreous electrolytes belonging to the Li₂Si₂O₅ Li₂SO₄ system has been measured over the temperature range 25–300 °C and for Li₂SO₄ concentrations varying from 0–28 mole percent. It has been found that the conductivity increases with the Li₂SO₄ fraction, attaining 10^?5 Ω^?1 cm^?1 at 130°C for the glass containing the highest proportion of sulphate. Raman spectroscopic studies indicate that the tetrahedral SO^2?₄ ions are in the glassy network, inserted or not into the silicate chains.     

Conductivite ionique dans les verres LiPO3LiX (X = I,Br, Cl)

The glass-forming regions in the systems LiPO₃LiX with X = I, Br, Cl were determined and the study of the electrical conductivity of glasses belonging to these systems was carried out. The conductivity increases with increasing halogen ion size and reaches maxima values of the order of 10^?6, 3, 2 10^?7, 10^?7 (ohm cm)^?1 at 25° C with LiI, LiBr, LiCl respectively : they are obtained at the limit of glass forming region. The Raman spectra do not show any modifications. The study of the electrical conductivity shows that the conduction is essentially ionic in nature.