Studies in Lithium Oxide Systems: I, Li2O B2O3–B2O3

Phase relationships in the system Li₂O, B₂O₃-B₂O₃ were studied by the quenching method using twenty compositions. The crystalline phases encountered were (a) Li₂O, B₂O₃, which melts congruently at 849°± 2°C., (b) Li₂O.-2B₂O₃, which melts congruently at 917°± 2°C., (c) a new compound, 2Li₂O-5B₂O₃, which melts incongruently at 856°± 2°C. and dissociates below 696°± 4°C., (d) Li₂O.3B₂O₃, which melts incongruently at 834°± 4°C. and dissociates below 595°± 20°C., and (e) probably Li₂O.4B₂O₃, which melts incongruently at 635°± 10°C. Reactions were sluggish at temperatures near 600°C., resulting in metastable relations. Hence phase equilibrium data relating to the lower stability limit of Li₂O.3B₂O₃ and to the upper stability limit of Li₂O.4B₂O₃ are considered to be tentative. Properties of the glasses and crystalline phases were studied. The refractive index of the glasses increased with the addition of Li₂O up to 22%, but further additions up to 40% had no substantial effect. Glasses containing less than 30% Li₂O were water soluble. Limited data on the density and thermal expansion of the glasses are presented. Li₂OB₂O₃ was euhedral, lath-shaped, length-fast, biaxial negative (2V = 27°), with n_α= 1.540, n_β= 1.612, n_γ= 1.616. Li₂O.2B₂O₃ was uniaxial negative, with n_e= 1.560, n_w= 1.605. Li₂O.3B₂O₃ was biaxial negative (2V = 75° to 80°), with n_α= 1.576, n_β= 1.602, n_γ= 1.605. X-ray powder diffraction data for the five crystalline compounds are presented. Thermal expansion data for Li₂O-B₂O₃ and Li₂O.2B₂O₃ and limited data on the fluorescent properties of the compounds are given. X-ray diffraction data are also presented for Li₂O.B₂O₃.4H₂O and Li₂O.-5B₂O₃. 10H₂O. Li₂O B₂O₃ was obtained by heating the first hydrate at 450° to 680° C. X-ray diffraction showed Li₂O.4B₂O₃ and Li₂O-3B₂O₃ to be the crystalline products obtained during heating the decahydrate at 500°C. and 600°C., respectively.     

Structure of vitreous lithium and cesium triborates

Glasses of the compositions Li₂O · 3B₂O₃ and Cs₂O · 3B₂O₃ have been investigated using X-ray diffraction. The isomorphous substitution of heavy cesium for light lithium makes it possible to rather accurately determine the B-O and O-O interatomic distances in the lithium-containing glass and the Cs-Cs interatomic distances in the cesium-containing glass. For the Li₂O · 3B₂O₃ glass, ten coordination shells are observed in the ordering region up to 7 Å. A comparison of the experimental and model atomic radial distribution functions has revealed that the structure of the glass contains groups similar to those observed in crystalline LiB₃O₅. They include at least two triborate groups bound via the oxygen atom. For the Cs₂O · 3B₂O₃ glass, ten coordination shells are revealed in the ordering region up to 12 Å. An analysis of the experimental atomic radial distribution curve in the framework of the fragmentary model has allowed the conclusion that cavities similar to those inherent in crystalline CsB₃O₅ are retained in the structure of the cesium-containing glass and contain up to three cesium atoms located at distances close to the corresponding distances in the crystal. The statistical mean coordination of the cesium atoms by oxygen atoms remains unchanged.     

Raman and dielectric spectra of the glass and single crystal of the composition Li2Ge7O15 in the frequency range 3–1000 cm−1: II. The influence of phase separation

The Raman spectra of Li₂O · 7GeO₂ glasses, which are heat treated under different conditions at temperatures near the temperature corresponding to the first exothermal peak in the DTA curve, are measured in the frequency range 20–1100 cm^?1. A comparative analysis of the measured spectra with the use of the data available in the literature and the X-ray diffraction results demonstrates that the glass undergoes phase separation and that phases of compositions close to GeO₂ and Li₂O · 4GeO₂ precipitate at the initial stage. The ordering of both phases varies significantly within the sample and, on the average, is substantially higher than that in the initial glass. This confirms the known assumptions made by researchers that crystal nuclei with a Li₂O · 4GeO₂ structure arise during heat treatment of lithium germanate glasses. At the phase separation stage under investigation, the phases are formed as nanoinhomogeneities that only slightly affect the transparency and, in the course of heat treatment, increase in size with a further ordering of the structure.     

Phase equilibria and thermodynamic properties of components in the Cs2O-B2O3-SiO2 system at high temperatures

The phase equilibria in the Cs₂O-B₂O₃-SiO₂ system are investigated in the temperature range 873–1073 K by the annealing-quenching technique, high-temperature microscopy, and X-ray powder diffraction analysis. The vapor composition, the activities of the components, and the Gibbs energies of glasses and melts in the Cs₂O-B₂O₃-SiO₂ system are determined at a temperature of 1020 K. It is demonstrated that glasses and melts in the Cs₂O · B₂O₃-Cs₂O · SiO₂ system are characterized by positive deviations of the CsBO₂ activities and negative deviations of the Cs₂O · SiO₂ activities from ideal behavior. As a consequence, the deviations of the Gibbs energies from ideal behavior change their sign.     

288 K下Li+,K+//CO2-3,B4O2-7-H2O四元体系的相平衡

Solubilities and properties (density, conductivity and pH value) of solutions in the quaternary system Li⁺,K⁺//CO^2-₃,B₄O^2-₇-H₂O at 288 K were experimentally studied with the isothermal equilibrium method. The phase diagram of the system consisted of two invariant points E and F, five univariant curves, and four crystallization fields that belonged to K₂CO₃·3/2H₂O,Li₂B₄O₇·3H₂O,K₂B₄O₇·4H₂O and Li₂CO₃. The composition of the solution corresponding to E was w（CO^2-₃）=2.27 %,w（B₄O^2-₇）=6.05 %,w（K⁺ ）=4.30%,w(Li⁺)=0.30 % and the equilibrium solids were Li₂B₄O₇· 3H₂O+K ₂B₄O₇·4H₂O+Li₂CO₃;The composition of the solution for F was w(CO^2-₃)=22.45%,w(B₄O^2-₇)=1.88%,w(K⁺ )=29.96%,w(Li⁺ )=0.03% and the equilibrium solids were K₂CO₃·3/2H₂O+K ₂B₄O₇·4H₂O+Li₂CO₃. K₂CO₃ possesses strong salting-out effect on K₂B₄O₇,Li₂CO₃ and Li₂B₄O₇.     

Raman Spectra and the Structure of Melts in the Na2O–P2O5–SiO2System

Raman spectra of melts in the Na₂O–P₂O₅–SiO₂system are measured at high temperatures. The differences between the Raman spectra of melts and glasses with identical compositions are considered. It is demonstrated that the structural inhomogeneity of the system slightly increases with a decrease in temperature and vitrification of the melt.     

New Li solid electrolytes

New Li-ion conductors with several different structure types are reported. Li₄B₇O₁₂(Cl,Br) and LiM₂P₃O₁₂ (MZr, Hf) have framework structures. The others are based on structures with isolated polyhedra in a network of edge-linked Li polyhedra and include Li_2+xC_1?xB_xO₃, Li_3?x B_1?xC_xO₃, Li_4+xSi_1?xSi_1?xAl_xO₄, Li_4?xSi_1?xP_xO₄, Li_4?2xSi_1?xS_xO₄ and Li _5?xAl_1?xSi_xO₄. Li_0.8Zr_1.8 Ta_0.2P₃O₁₂ has the best room temperature conductivity, ～5 × 10^?6 (Ωcm)_?1. At 300°C, the conductivities of Li_3.75Si_0.75P_0.25O₄, Li_3.4Si_0.3O₄ and Li_2.25C_0.75B_0.25O₃ are 1 × 10^?2 (Ωcm)^?1. These compositions resist attack by molten li at 200°C and some can be easily prepared as dense ceramics.     

The System Bi2O,—B2O3

The phase diagram for the system Bi₂O₃-B₂O₃ has been determined experimentally. The melting point of Bi₂O₃ has been redetermined as 825° C with an estimated overall uncertainty of about ±3°C, and the molal heat of fusion of Bi₂O₃, calculated from the slope of the liquidus curve, is 2050 cal per mole. The system contains a body-centered cubic phase of approximate composition 12Bi₂O₃·B₂O₃, which melts incongruently at 632°C. Four congruently melting compounds exist in the system: 2Bi₂O₃· B₂O₃·5B₂O₃, Bi₂O₃·3B₂O₃, and Bi₂O₃·4B₂O₃, with melting points, respectively, of 675°, 722°, 708°, and 715°C. The Bi₂O₃·4B₂O₃ compound exhibits a sluggish transformation at 696°C. Compositions containing up to 97.5 wt% (85 mole %) Bi₂O₃ can be partly or totally quenched to glass. Indices of the quenched glasses are greater than 1.74. A region of liquid immiscibility extends at 709°C from almost pure B₂O₃ to 19.0 mole % Bi₂O₃. The extent of immiscibility theoretically calculated agrees with the experimentally determined value when 1.20 A is used for the ionic radius of Bi³⁺.     

Raman and dielectric spectra of the glass and single crystal of Li2Ge7O15 in the frequency range 3–1000 cm−1: I. Comparison of the structures of the crystal and initial glass

The Raman and dielectric spectra of vitreous and single-crystal lithium heptagermanates are measured over a wide range of frequencies from 3 to 1000 cm^?1. It is revealed that the spectra of the Li₂O · 7GeO₂ glass and the Li₂Ge₇O₁₅ crystal are similar to each other because the intense but broad bands in the spectrum of the glass correspond to the most intense groups of bands in the spectrum of the crystal. The similarity is observed over the entire frequency range, including the range of the boson peak. This indicates that the shortrange orders in the structures of the glass and the crystal are similar to each other and that the medium-range order in the glass resembles the main structural motif of the crystal.     

Extraction of titanium dioxide (TiO2) from ilmenite and titaniferous slag

Solutions of ilmenite (FeTiO₃) and a titaniferous slag, in fused Li₂O. 2B₂O₃ and Li₂O. 4B₂O₃, yield on cooling compounds tentatively identified as LiFe₂.₅Ti₃O₉ and Li₂Fe₃Ti₂.₅O₉ respectively. Both compounds are orthorhombic, and have the pseudobrookite structure. The ilmenite solutions yield, in addition, rutile (TiO₂). The yield of rutile increases from about 1 to 24% (w/w) of the products, when the solvent is changed from Li₂O. 2B₂O₃ to Li₂O. 4B₂O₃. Substitution of K₂O. 4B₂O₃ for the latter solvent decreases the yield of rutile to c. 10%. The yield of rutile is approximately in inverse proportion to the Lux—Flood basicity of the borate solvent.     

Structure of Cs2O-B2O3 glass and melts: The Raman spectroscopy data

The study continues a series of works of the authors dedicated to the investigation of the alkaliborate glass and melts, in order to determine the structure of samples of the xCs₂O-(100 ? x)B₂O₃ (x ≤ 40 mol %) composition in glassy, supercool, and molten conditions with the high-temperature Raman spectroscopy. The Raman spectra were analyzed to identify the type of structural units in glass and melts and the variation in structure depending on composition and temperature.     

Silver Co-Firable ZnTiNb2O8 Microwave Dielectric Ceramics with Li2O–ZnO–B2O3 Glass Additive

The effects of Li₂O–ZnO–B₂O₃ glass additive on the sintering behavior, phase formation, microstructure, and microwave dielectric properties of ZnTiNb₂O₈ ceramics have been investigated. The sintering temperature of ZnTiNb₂O₈ ceramics can be effectively reduced from 1200°C to 875°C by adding a small amount of Li₂O–ZnO–B₂O₃ glass, while no obvious degradation of the microwave dielectric properties was induced. Typically, the 2.0 wt% Li₂O–ZnO–B₂O₃ glass-added ceramic sintered at 875°C has better microwave dielectric properties of ɛ_r=31.8, Q×f=25,013 GHz, and τ_f=−62 ppm/°C. In addition, the ceramics can be co-fired well with an Ag electrode.     

Medium-range order and physicochemical properties of (100 ? x)(0.5PbO · 0.5P2O5) · xTeO2 glasses in terms of the constant stoichiometry grouping concept

Glasses in the (100 − x)(0.5PbO · 0.5P₂O₅) · xTeO₂ section of the PbO-P₂O₅-TeO₂ system have been synthesized over the entire composition range for the first time and their properties (Raman spectra, refractive index n, density d, glass transition temperature T _g , and light scattering losses) have been investigated. It has been demonstrated that the Raman spectra can be represented as a superposition of constant spectral forms corresponding to constant stoichiometry groupings PbO · P₂O₅, TeO₂ · 2PbO · 2P₂O₅, TeO₂ · PbO · P₂O₅, 2TeO₂ · PbO · P₂O₅, and TeO₂. The existence of crystals of the corresponding stoichiometry has been predicted using the constant stoichiometry grouping concept. The diagram of the constant stoichiometry grouping contents (determined from the Raman spectra) in glasses of the system under investigation has made it possible to determine the partial properties of constant stoichiometry groupings, to calculate the dependences of the refractive index and density on the composition, and to refine the values of n and d for vitreous tellurium dioxide and lead metaphosphate. The practical importance of glasses in the system under consideration for the use in photonic devices has been discussed.     

Crystallization of glasses in the SrO-B<Subscript>2</Subscript>O<Subscript>3</Subscript> system

The crystallization of strontium borate glasses containing 16.7–43.0 mol % SrO is investigated. New crystalline compounds of the hypothetical compositions 2SrO · 3B₂O₃ (metastable) and SrO · 5B₂O₃ (stable below 750°C), as well as the metastable diborate modification β-SrO · 2B₂O₃, are revealed, and their X-ray powder diffraction data are obtained. It is demonstrated that, with a deficit of strontium oxide, the 4SrO · 7B₂O₃ compound forms solid solutions. Strontium triborate SrO · 3B₂O₃, which was previously prepared only through the dehydration of crystal hydrates, is produced using crystallization of glasses. The thermal stability of this compound is studied. The influence of the dispersity on the stability of different crystalline phases is discussed. Variants of the phase diagram for the SrO · B₂O₃-B₂O₃ system in the case of monolithic and dispersed samples are proposed from analyzing the experimental results and the data available in the literature.     

THE SYSTEM MAGNESIUM OXIDE-BORIC OXIDE*

Equilibrium In the system has been investigated for compositions from 0.6 to 75 weight per cent MgO. Three intermediate compounds are present. MgO⋅B₂O₃ melts incongruently at 988°C. to form 2MgO⋅B₂O₃ and a liquid containing more than 99% B₂O₃. The other two compounds melt congruently: 2MgO⋅B₂O₃ at 1340°C. and 3MgO⋅-B₂O₃ at 1366°C. At 1142°C., a region of liquid immiscibility extends from 0.6 to 36.0% MgO. Temperatures are accurate within =5°C. Conflicts between these results and those of Toropov and Konovalov (see footnote 8) are discussed.     

Relationship between glass network structure and conductivity of Li2O-B2O3-P2O5 solid electrolyte

Solid state glass electrolyte, xLi₂O-(1 − x)(yB₂O₃-(1 − y)P₂O₅) glasses were prepared with wide range of composition, i.e. x = 0.35 - 0.5 and y = 0.17 - 0.67. This material system is one of the parent compositions for chemically and electrochemically stable solid-state electrolyte applicable to thin film battery. Lithium ion conductivity of Li₂O-B₂O₃-P₂O₅ glasses was studied in the correlation to the structural variation of glass network by using FTIR and Raman spectroscopy. The measured ionic conductivity of the electrolyte at room temperature increased with x and y. The maximum conductivity of this glass system was 1.6 × 10⁻⁷ Ω⁻¹ cm⁻¹ for 0.45Li₂O-0.275B₂O₃-0.275P₂O₅ at room temperature. It was shown that the addition of P₂O₅ reduces the tendency of devitrification and increases the maximum amount of Li₂O added into glass former without devitrification. As Li₂O and B₂O₃ contents increased, the conductivity of glass electrolyte increased due to the increase of three-coordinated [BO₃] with a non-bridging oxygen (NBO).     

SELENIUM DIOXIDE AS A CONSTITUENT OF GLASSES1

SeO₂ is added as selenious acid (H₂SeO₃) and as sodium selenite (Na₂SeO₃ to the oxides Na₂O, CaO, BaO, PbO, B₂0₃, and SiO₂ to form glasses and crystalline melts containing apprcciable amounts of SeO₂. The chemical analysis of glasses shows the vaporization of SeOn to be high during the melting stage. Most of these glasses are unstable in air or water. A relatively stable glass contained Na₂O 33.4%, CaO 12.4%, B₂O₃ 37.6%, SiO₂ 5.8%, SeO₂ 10.8%. Melting several compositions in a closed container yielded opaque or crystalline melts, whereas the same compositions melted in air with a partial volatilization of SeO₂ gave clear glasses.     

Structure of glasses and melts in the Na<Subscript>2</Subscript>O-B<Subscript>2</Subscript>O<Subscript>3</Subscript> system from high-temperature Raman spectroscopic data: I. Influence of temperature on the local structure of glasses and melts

The local structure of glasses and melts in the Na₂O-B₂O₃ system in the composition range 10–30 mol % Na₂O is investigated by high-temperature Raman spectroscopy in the temperature range 20–1150°C. The recorded spectra are analyzed by simulating the experimental spectra in the form of a superposition of the set of Gaussian lines. The results of the simulation are used to determine the concentrations of the main structural units of borates as a function of the composition and temperature. The dynamic equilibrium of the interaction between the structural units in melts has the form

$B_{4/2}^ - \rightleftarrows B_{2/2} O^ - $

and shifts toward the right, i.e., toward the formation of BØ₂O^? metaborate triangles (where Ø is a bridging oxygen atom), with an increase in temperature. The enthalpy of the disproportionation process depends on the melt composition and increases with an increase in the oxide modifier concentration.

     

A lithium aluminium borate composite microwave dielectric ceramic with low permittivity,near-zero shrinkage,and low sintering temperature

A low temperature co-fired dielectric material with low shrinkage during the sintering process can enhance the circuit design of electronic devices. Lithium aluminium borate composite ceramic with a composition of Li₂O:Al₂O₃:B₂O₃ = 1:1:2 (abbreviated: LAB) was prepared by a traditional solid-state reaction method. These ceramics have a low sintering temperature (675–750 °C), low permittivity, and near-zero shrinkage. When the sintering temperature was 725 °C, the LAB ceramics exhibited a small shrinkage of ?2.4% and the best microwave dielectric properties with ε_r = 3.9, Q × f = 35 500 GHz, and τ_?= ?64 ppm/°C. The LAB ceramics sintered at 700 °C have near-zero shrinkage of ? 0.4% and good microwave dielectric properties. The ceramics transformed from (Li₂B₄O₇ and Al₂O₃) to (Li₂Al₂B₄O₁₀ and Li₄Al₄B₆O₁₇) phases with increasing the sintering temperature, which may be the reason why they show marginal shrinkage. In addition, the ceramics could be co-fired with Ag, indicating that this material is a good candidate for low-temperature co-fired ceramic devices.     

Simulation of the thermodynamic properties of glass-forming melts in the Na2O-B2O3-SiO2 system in the framework of the generalized lattice theory of associated solutions

The possibility of calculating the thermodynamic properties of melts in the Na₂O-B₂O₃-SiO₂ system (as in the previously studied Cs₂O-B₂O₃-SiO₂ system) formed by two glass-former oxides (B₂O₃, SiO₂) and one modifier oxide (Na₂O) with the use of the vacancy variant of the generalized lattice theory of associated solutions is demonstrated. A comparison with the experimental thermodynamic functions previously determined by the electromotive force method and high-temperature mass spectrometry at temperatures of 1200, 1273, and 1350 K shows that the calculations performed within this approach lead to reliable thermodynamic functions. It is noted that the proposed model ignores the change in the coordination number of boron atoms to four and the possibility of forming associates in melts of compositions lying in the metastable phase separation region at temperatures higher than the phase separation temperature.