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-PbF2-LaF3-NaF system

Glass formation in the ZrF₄-PbF₂-LaF₃-NaF system is studied by differential thermal analysis at ZrF₄ contents of 65 and 70 mol %. The glass-forming region is outlined, and the composition dependences of glass stability parameters are presented.     

Glass formation in the ZrF<Subscript>4</Subscript>-MF<Subscript>2</Subscript>-LaF<Subscript>3</Subscript>-NaF (M - Ba,Pb) systems

Glass formation in the ZrF₄-MF₂-LaF₃-NaF (M - Ba, Pb) systems has been studied by differential thermal analysis, and the thermal parameters of the glasses have been determined. Using glass stability criteria, the most stable ZMLN glass compositions have been identified.     

Annealing of electron damage in Mid-IR transmitting fluoride glass

Damage in ZrF₄-BaF₂-LaF₃ glass induced by high energy electrons was studied by electron spin resonance (ESR) and optical spectroscopy. An optical absorption band at 314 nm in the irradiated glass annealed rapidly above about 50°C, probably by a second-order reaction at room temperature; the ESR lines annealed very slowly at room temperature.     

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.     

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.     

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.     

Synthesis, IR, crystallization and dielectric study of (Pb, Sr)TiO 3 borosilicate glass–ceramics

Eleven glass compositions were prepared by melt and quench method with progressive substitution of SrO for PbO (0?≤?x?≤ 1·0) with a step-wise increment of 0·10 in the glass [(Pb _x Sr_1???x )OTiO₂]–[(2SiO₂B₂O₃)]–[BaO·K₂O]·Nb₂O₅ (mol percentage) system. The infrared spectra (IR) of various glass compositions in the above mentioned glass system was recorded over a continuous spectral range 400–4000 cm^???1 to study their different oxides structure systematically. Differential thermal analysis (DTA) was recorded from room temperature (~27 °C) to 1400 °C employing a heating rate of 10 °C /min to determine glass transition temperature, T _g and crystallization temperature, T _c. The melting temperature, T _m, of these glass compositions was found to be in the range 597–1060 °C depending on the composition under normal atmospheric conditions. T _g and T _m of glasses were found to increase with increasing SrO content. X-ray diffraction analysis of these glass–ceramic samples shows that major crystalline phase of the glass–ceramic sample with x ≤ 0·5 was found to have cubic structure similar to SrTiO₃ ceramic. Scanning electron microscopy has been carried out to see the surface morphology of the crystallites dispersed in the glassy matrix.     

The effect of nitrogen addition on certain properties and structure of fluorozirconate glasses

The effect of nitrogen on the properties and structure of fluorozirconate glasses in the system ZrF₄-BaF₂-LaF₃-AlF₃ (ZBLA) was investigated. Nitrogen was introduced by means of aluminium nitride. The substitution of fluorine by nitrogen in ZBLA glasses resulted in a considerable increase of microhardness, reduction of the linear expansion coefficient, and a small increase in characteristic temperatures. Structural investigations comprised RDF and Fourier transform-infrared (FT-IR) examinations. From radial distribution function (RDF) it followed that the introduction of nitrogen caused an increase of the mean distances Zr-F(N), Ba-F(N), La-F(N). From FT-IR spectra, it followed that nitrogen became incorporated into the bridging fluorine atoms which was evinced by a shifting of bands deriving from the bending vibrations between the [ZrF₆]^2– octahedra towards higher wave numbers.     

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.     

Oxide ionic conductivity and crystallographic properties of tetragonal type Bi2O3-based solid electrolyte doped with Ho2O3

Abstract

In the present work, the authors have investigated the binary system of (Bi₂O₃)_1–x(Ho₂O₃)_x. For the stabilisation of the tetragonal type solid solution, small amounts of Ho₂O₃ were doped into the monoclinic Bi₂O₃ via solid state reactions in the stoichiometric range 0·01≤x≤0·1. The crystal formula of the formed solid solution was determined as Bi(III)_4–4xHo(II)_4xO_6–2xVo_(2+2x) (where Vo is the oxide ion vacancy) according to the XRD and SEM microprobe results. In the crystal formula, stoichiometric values of x were 0·04≤x≤0·08, 0·03≤x≤0·09, 0·02≤x≤0·09 and 0·04≤x≤0·09 for annealing temperatures at 750, 800, 805 (quench) and 760°C (quench) respectively. The four probe electrical conductivity measurements showed that the studied system had an oxide ionic type electrical conductivity behaviour, which is increased with increasing dopant concentration and temperature. The obtained solid electrolyte system has an oxygen non-stoichiometry characteristic, and it contains O^2– vacancies, which have disordered arrangements in its tetragonal crystal structure. The increase in the amount of Ho₂O₃ doping and temperature causes an increasing degree of the disordering of oxygen vacancies and a decrease in the activation energy E_a.     

Investigation of the dominant point defects in tetragonal YBa2Cu3Ox at elevated temperatures

The manner in which oxygen is incorporated into YBa₂Cu₃O _x (YBCO) at ～800°C for values ofx close to 6 is shown to be in the form of neutral oxygen interstitials, O _i ^x . The experimental data on which this conclusion is based are obtained from measurements of oxygen partial pressure,P(O₂), as a function of compositionx and temperatureT (5.99≤x≤ 6.35, 825≤T≤1120 K). The data are obtained by a solid-state electrochemical method. Other conclusions of this study include: (a) O _i ^x are noninteracting forx ? 6. (b) The stoichiometric composition of YBCO isx ? 6.0. (c) The reaction enthalpy of oxidation is 179 kJ/mol O₂. (d) The Fermi level changes by ? ?0.2 eV asx increases from 6.05 to 6.35.     

Microwave dielectric properties of mixed phase ceramics, Ba(Zn1/3Ta2/3)O3–xCaTiO3 and xMgTiO3–yCaTiO3–z(Nd2O3,wTiO2)

The effect of different chemical compositions on the microwave dielectric properties of Ba(Zn_1/3Ta_2/3)O₃–xCaTiO₃ and xMgTiO₃–yCaTiO₃–z(Nd₂O₃,wTiO₂) was studied. High fQ dielectrics were designed by optimizing composition and firing conditions. Adding up to 1 mol % CaTiO₃ to Ba(Zn_1/3Ta_2/3)O₃ increased ε_r from 25 to 30 at a firing temperature of 1450 °C, and produced very high fQ values of more than 100 000 GHz at a firing temperature of 1550 °C. EPMA and XRD suggested that ceramics based on Ba(Zn_1/3Ta_2/3)O₃ with CaTiO₃ had mixed phases of Ba(Zn_1/3Ta_2/3)O₃ and Ca–Ti–Zn–O. Addition of CaTiO₃ increased the Ba(Zn_1/3Ta_2/3)O₃ peak observed in XRD and decreased the Ba₃Ta₂O₈ peak. Prolonged sintering of Ba(Zn_1/3Ta_2/3)O₃ with CaTiO₃ increased the fQ value but kept ε_r constant. 0.5MgTiO₃–0.5CaTiO₃–z(Nd₂O₃,wTiO₂) showed a high dielectric constant ε_r>40 and fQ>20 000 GHz. When w=1, τ_f decreased linearly with z around 0 ppm/ °C in 0.5MgTiO₃–0.5CaTiO₃–z(Nd₂O₃,TiO₂) (0.25≤z≤0.5). X-ray and EDX analysis revealed a mixed phase matrix of MgTiO₃ and (Ca_1?αNd_2α/3)Ti_βO₃. It was concluded that ε_r of the high fQ materials Ba(Zn_1/3Ta_2/3)O₃–xCaTiO₃ and xMgTiO₃–yCaTiO₃–z(Nd₂O₃,wTiO₂) would be increased by varying their chemical compositions, x, y, z, and w, and that their fQ value would be improved by appropriate choices of heating temperature and time.     

Preparation and properties of heavy-metal halide glasses

We have studied the effect of In³⁺, Pb²⁺, Gd³⁺, and Cl (heavier ions) substitutions for Al³⁺, Ba²⁺, La³⁺, and F^? on the crystallization stability and UV/IR optical properties of HBLAN fluorohafnatc glasses (HfF₄-BaF₂-LaF₃-AlF₃-NaF system). We obtained stable glasses containing InF₃ and BaCl₂ instead of AlF₃ and BaF₂, respectively, and offering increased IR transmission. The presence of CCl₄ in the process atmosphere and the removal of oxygen-containing impurities via directional solidification are shown to have an advantageous effect on the optical quality of the glasses. The fluoride-chloride glasses are capable of accommodating about 1.5 times higher levels of rare-earth activators in comparison with their fluoride analogs.     

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.     

Solid-phase crystallization of amorphous SiGe films deposited by LPCVD on SiO2 and glass

The crystallization kinetics and film microstructure of poly-SiGe layers obtained by solid-phase crystallization (SPC) of amorphous SiGe with Ge fractions (x) in the 0 to 0.42 range have been studied in detail. Amorphous SiGe layers 100 nm thick were deposited by LPCVD at 450°C on thermally oxidized Si wafers and 7059 Corning glasses, using Si₂H₆ and GeH₄ as gas sources. The samples were crystallized at 550°C and low pressure (below 9 Pa). The evolution of the crystallization and the resulting film microstructure were characterized by X-ray diffractometry and transmission electron microscopy. The experimental results on growth kinetics fit the Avrami’s model. The characteristic crystallization time decreases with x, slowly for x<0.3 and more abruptly for higher values of x. The transient time depends exponentially on x in all the intervals. The crystallized films have a (111) preferred orientation for low values of x and evolve to a randomly oriented polycrystal as x increases. The grain size in the fully crystallized layers decreases with increasing x. The results are similar for the films deposited on silicon dioxide and glass.     

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.     

Light scattering investigation on a fluorozirconate glass

Light scattering characteristics for a fluorozirconate glass, ZrF₄(60)-BaF₂(32)-GdF₃(4)-AlF₃(4mol%), were measured. It was clarified that the light scattering depended remarkably upon the melt cooling rate through the crystallization temperature. In case of the low cooling rate, the glass had enormous Rayleigh's ratio, R₉₀o, with strong forward scattering and exhibited a large anisotropic light scattering. AlF₃ segregation was presumed to be an origin for the strong forward scattering. While, as the melt cooling rate was increased up to 33 °C/min., almost Rayleigh scattering aspect was observed and a relatively small Rayleigh's ratio R₉₀o = 5.34×10^?6 cm^?1 was obtained at 0.633 μm, which was comparable to those for some optical glasses. Based on the Rayleigh's ratio measured here, it is suggested that the scattering loss estimated by the $\text{1}\text{λ}{}^4$ law becomes less than 0.1 dB/km at the 3 μm band.     

Mechanochemical synthesis of SnO-B2O3 glassy anode materials for rechargeable lithium batteries

The xSnO·(100 ? x)B₂O₃ (0 ≦ x ≦ 80) glasses were successfully prepared by a mechanical milling technique. The glass with 40 mol% SnO showed the maximum glass transition temperature of 347°C. The SnO-B₂O₃ milled glasses consisted of both BO₃ and BO₄ units, and the fraction of BO₄ units was maximized at the composition of 50 mol% SnO. The electrochemical properties of the milled glasses were examined using a simple three electrodes cell with a conventional liquid electrolyte. The glasses with high SnO content exhibited high charge capacities more than 1100 mAh g^?1 and discharge capacities more than 700 mAh g^?1 at the first cycle. The SnO-B₂O₃ milled glasses proved to work as anode materials for rechargeable lithium batteries.