Copper ⇌ Alkali Ion Exchange of Alkali Aluminosillcate Glasses in Copper-Containing Molten Salt: I, Monovalent Copper Salt, CuCl

Cu⁺⇌ R⁺ (R = Li, Na, and K) ion exchange experiments were conducted for 20R₂O·10Al₂O₃·70SiO₂ glasses in molten CuCl at 550°C in air and nitrogen atmospheres. The depth profiles of the copper incorporated into glasses were determined with an electron microprobe X-ray analyzer. The total amount of diffusing copper, M _t, strongly depended on the type of alkali ion in the glass and the ion-exchange atmosphere; i.e., M _t increased with increasing cationic size in the order Li < Na < K and M _t was greater in air than in nitrogen. The Cu ⇌ R⁺ ion exchange kinetics are discussed in detail.     

Copper-Alkali Ion Exchange of Alkali Aluminosilicate Glasses in Molten CuCl—An Ion Exchange Controlled by the Cu+→Cu2+ Oxidation Reaction in Glass

The kinetics of copper-potassium ion exchange of potassium aluminosilicate glass have been investigated in molten CuCl at 550°C in air and nitrogen. The presence of oxygen dissolved in molten CuCl has a great effect on the Cu-K ion-exchange kinetics, i.e. ion exchange in nitrogen is controlled by the interdiffusion process of Cu⁺ and K⁺ in the glass, whereas ion exchange in air seems to be controlled by the Cu⁺→Cu²⁺ oxidation reaction.     

Electrical Properties of Superionic Conducting Glasses in the Pseudobinary System CuI-Cu2MoO4

Cu⁺-ion-conducting glasses were prepared in the pseudo-binary system CuI-Cu₂MoO₄. These glasses have high ionic conductivities at room temperature in the range 10⁻¹ to 10° S·m⁻¹, which are 10 to 20 times greater than those of the Ag⁺-ion-conducting glasses with the same iodide contents in the system AgI-Ag₂MoO₄. The conductivities increase with increasing CuI content. The increase in the conductivity can be explained in terms of a decrease in the activation energy for conduction. The electronic conductivity was measured by the Wagner polarization method and indicates that the transport number of Cu⁺ ions in those glasses is 0.9996 and larger.     

Formation of Sm2+ lons in Sol-Gel-Derived Glasses of the System Na2 O-Al2O3-SiO2

Samarium ions (Sm²⁺) incorporated into aluminosilicate glasses by a sol-gel process showed persistent spectral hole burning at room temperature. Gels of the system Na₂O-Al₂O₃SiO₂ synthesized by the hydrolysis of Si(OC₂H₅)₄, Al(OC₄H₉)₃, CH₃ COONa, and SmCl₃·6H₂O were heated in air at 500°C, then reacted with H₂ gas to form Sm²⁺ ions. Whereas Al³⁺ ions effectively dispersed the Sm³⁺ ions in the glass structure, Na⁺ ions were not effective. The Al₂O₃-SiO₂ glasses proved appropriate for reacting the Sm³⁺ ions with H₂ gas and exhibited the intense photoluminescence of Sm²⁺ ions. The reaction of Sm³⁺ ions with H₂ in the Al₂O₂-SiO₂ glasses was determined by first-order kinetics, and the activation energy equaled 95 kJ/mol. At 800°C, the maximum photoluminescence of the Sm²⁺ ions was achieved within 20 min.     

Formation of ZnAl2O4 in the Presence of Cl2

The formation of ZnAl₂O₄ spinel in diffusion couples of Al₂O₃ and ZnO was investigated between 1000° and 1390°C in air and in air containing 4.8 vol% Cl₂ by X-ray diffraction, electron probe microanalysis, and scanning electron microscopy. The rate of formation of a spinel layer obeyed a parabolic rate law and was accelerated remarkably by the presence of Cl₂. The interdiffusion coefficient, , and the activation energy, E, were calculated to be 10⁻⁸ to 10⁻⁹ cm²/s and 123 kcal/mol (514 kJ/mol) in air and 10⁻⁷ cm²/s and 31 kcal/mol (130 kJ/mol) in air containing 4.8 vol% Cl₂, respectively.     

Kinetics of Nonisothermal Crystallization of Bi2Sr2CaCu2Ox Glasses with Different Copper Valence States

The kinetics of the nonisothermal crystallization process in Bi₂Sr₂CaCu₂O_x glasses with different copper valance states, R(Cu⁺) = Cu⁺/(Cu⁺+ Cu²⁺) = 0.79–0.99, were examined by using differential scanning calorimetry. Four different kinetic equations were used for the data analyses. It was found that the values of activation energy for crystal growth, E _a, decreased with increasing Cu⁺ content. The value of E _a, which was estimated from the modified Ozawa equation, for the glass with R(Cu⁺) = 0.79 was 483 kJ·mol^-1 and for the glass with R(Cu⁺) = 0.99 was 353 kJ·mol^-1. In the former glass, the number of crystal nuclei was almost independent of the heating rate. But, in the latter glass, the number of crystal nuclei varied significantly with the heating rate. The crystallization mechanism in the glasses was closely related to the thermal stability and viscosity of glasses: the glass with R(Cu⁺) = 0.99 showing a high thermal stability and a low activation energy for viscous flow had a small value of E _a. The plot of In ( T _p²/α) against 1/ T _p, where T _p and α are crystallization peak temperature and heating rate, respectively, gave a reasonable value of E _a for the glass with R(Cu⁺) = 0.79 but was unsuitable for the evaluation of E _a for crystal growth of the glass with R(Cu⁺) = 0.99.     

Infrared Spectra of Rapidly Quenched Glasses in the Systems Li2O-RO-Nb2O5 (R=Ba, Ca, Mg)

Twin-roller quenching produced wide ranges of glass formation in the systems Li₂O-RO-Nb₂O₅ (R=Ba,Ca,Mg). The glass-forming ability is improved with an increase in the ionic radius of R²⁺ ions. The crystallization temperature is increased as Li₂O is replaced by RO or the ionic radius of R²⁺ ions is increased. Infrared spectra revealed that the glass LiNbO₃ (=50Li₂O-0Nb₂O₅) was composed of six-coordinated NbO₆ octahedra, which were joined together by corner-sharing only. In the Li₂O-RO-Nb₂O₅ glasses there exist edge-shared as well as corner-shared NbO₆ octahedra. The edge-shared NbO₆ octahedra in the glasses are increased with an increase in the content of RO or Nb₂O₅, and also with an increase in the ionic radius of R²⁺ ions.     

Kinetic Study of Cu+−Cu2+ Equilibrium in Sodium Na2O−Al2O3−B2O3 Glass

The Cu⁺−Cu²⁺ equilibrium in sodium aluminoborate glass with an air atmosphere was studied at 950°, 1050°, and 1150°C. Equations suggested to represent the equilibrium reaction between oxidized and reduced species and oxygen were critically examined. An equation to represent the Cu⁺−Cu²⁺ equilibrium reaction was suggested. The reaction was observed to follow first-order kinetics. Enthalpy of the reaction was—12.5 kcal/mol.     

Chemical Strengthening of Glass-Ceramics in the System Li2O-Al2O3-SiO2

Fine-grained glass-ceramics containing a large proportion of β-spodumene solid-solution crystals were strengthened by immersion in molten sodium and potassium salt baths. An ion-exchange reaction placed sodium or potassium ions in lithium ion sites in the β-spodumene structure. The resultant "crowding" of the structure produced a surface compressive layer. In this system, strengths (modulus of rupture on abraded specimens) in excess of 100,000 psi were realized. In a similar manner, stuffed β-quartz solid-solution glass-ceramics derived from the crystallization of Li₂O-Al₂O₃-SiO₂ glasses containing an appropriate amount of nucleating agent were strengthened by K⁺-for-Li⁺ exchange. Stable β-quartz solid-solution glass-ceramics were strengthened by Na⁺-for-Li⁺ exchange, but no significant increase in strength was obtained in the metastable β-quartz materials.     

Ion Exchange in Alkali Layers of Potassium β -Ferrite ((1 + x)K2O · 11Fe2O3) Single Crystals

The potassium ions in potassium β-ferrite ((1 + x)K₂O ·11Fe₂O₃) crystals were exchanged with Na⁺, Rb⁺, Cs⁺, Ag⁺, NH₄⁺, and H₃O⁺ in molten nitrates or in concentrated H₂SO₄. On the other hand, spinel and hexagonal ferrites were formed by soaking the crystals in the melt of divalent salts. The crystals of K⁺, Rb⁺, and Cs⁺β-ferrites decomposed to form α-Fe₂O₃ at high temperatures of 800° to 1100°C. In addition, H₃O⁺, NH₄⁺, and Ag⁺β-ferrites decomposed to form α-Fe₂O₃ at relatively low temperatures of 350° to 650°C, in accordance with the stabilities of the inserted ions. The electrical properties of some β-ferrites were measured.     

Mechanical Damping Spectrum for Mixed-Alkali R2 O·Al2 O3·6SiO2 Glasses

The internal friction of R₂O·Al₂O₃·6SiO₂ glasses was measured from-180° to 700°C at 0.4 Hz. Glasses containing Li₂O or Na₂O exhibited only the one internal friction peak characteristic of the stress-induced movement of the alkali ions. Substitution of a second alkali resulted in two significant changes in the internal friction: (1) a rapid reduction in the magnitude of the original alkali peak and (2) the appearance of a new internal friction peak whose magnitude was especially sensitive to the concentration of the second alkali. Each combination of two alkali ions resulted in a new peak, with peaks being observed for the combinations Li-Na, Na-K, and Li-K. A mechanical damping spectrum is predicted for aluminosilicate glasses containing more than two alkali ions.     

Phase Equilibria and Structural Species in NdCl3–NaCl, NdCl3–CaCl2, PrCl3–NaCl, and PrCl3–CaCl2 Systems

Equilibrium phase diagrams for the systems NdCl₃–CaCl₂ and NdCl₃–NaCl were determined by differential thermal analysis. A simple eutectic was observed at 59 ± 1 mol% CaCl₂ and 600°± 2°C in the NdCl₃–CaCl₂ system. A compound NaCl.3NdCl₃ which melts incongruently at 545°± 5°C to NdCl₃ and a liquid containing approximately 47 mol% NaCl, and a eutectic at 68 mol% NaCl and 439°± 2°C were found in the NdCl₃–NaCl system. On the basis of agreements between the activities calculated by the Clausius–Clapeyron equation and Temkin's model using the present data for the NdCl₃–CaCl₂ system and the literature data for the PrCl₃–CaCl₂ system, the melts in the former system consist of Nd³⁺, Ca²⁺, and Cl⁻ ions and in the latter system of Pr³⁺, Ca²⁺, and Cl⁻ ions. The above approach indicates the presence of Na⁺, Cl⁻, and NdCl^2-₅ ions in the NaCl-rich melts and Nd³⁺, Cl⁻, and NdCl⁻₄ in the NdCl₃-rich melts in the NdCl₃–NaCl system. Analogous ions were indicated in the melts of the PrCl₃–NaCl system.     

Stannous-Stannic Equilibrium in Molten Binary Alkali Silicate and Ternary Silicate Glasses

The stannous-stannic equilibrium in binary alkali silicate and ternary silicate glasses was studied by equilibrating glassmelts with air at 1400°C. The Sn²⁺-Sn⁴⁺ equilibrium shifts more toward the oxidized state with increasing ionic radii of the alkali ions or with increasing concentration of the alkali ions in the same series of glasses. The slope of the straight lines obtained on plotting log (Sn⁴⁺)/(Sn²⁺)( pO₂ )^n/2 vs mol% R₂O increased in the order Li→Na→K. In ternary silicate glasses having the base glass composition 20Na₂O·10RO·70SiO₂, the Sn²⁺-Sn⁴⁺ equilibrium shifts more toward the reduced state, with increasing bond strength between the divalent cations and the nonbridging oxygens. With increasing temperature, the equilibrium shifts more toward the reduced state.     

Chemical Durability of Sodium Silicate Glasses Containing AI2O3 and ZrO2

A sodium silicate glass and ternary glasses derived from it by substituting AI₂O₃ and ZrO₂ for SiO₂ were exposed to water and aqueous solutions of pH 1.4 to 12.7; the kinetics of the reactions were studied. Diffusion of alkali ions and leaching of alkali and SiO₂ from the glasses were influenced by the occupancy of surface sites by alkali ions above a critical pH; however, the activation energies of the processes varied linearly with the logarithm of mole fraction of surface sites occupied by H^plus;. Identical slopes were obtained for all glasses for a given process. The results are explained on the basis that transport of alkali ions is retarded as a result of increased boundary concentration and that suitable sites for reaction are lacking.     

Phase Equilibria and Structural Species in MgF2-MgO, MgF2-CaO, and MgF2-Al2O3 Systems

Partial equilibrium phase diagrams for the systems MgF₂-MgO, MgF₂-CaO, and MgF₂-Al₂O₃ were determined by differential thermal analysis. Simple eutectics were observed at 8.5 mol% MgO and 1228°± 3°C in the MgF₂-MgO system, at 7.5 mol% CaO and 1208°± 3°C in the MgF₂-CaO system, and at 2.5 mol% Al₂O₃ and 1250°± 3°C in the MgF₂-Al₂O₃ system. On the basis of agreements between the activities calculated by the Clausius-Clapeyron equation and Temkin's model using the present data, the eutectic melt consists of Mg²⁺, F^-, and O^2- ions in the MgF₂-MgO system; Mg²⁺, Ca²⁺, F^-, and O^2- ions in the MgF₂-CaO system; and Mg²⁺, Al³⁺, F^-, and AlO_2¯ ions in the MgF₂-Al₂O₃ system. Well-defined long needles of MgO in the MgF₂-MgO system, less defined needles of CaO in the MgF₂-CaO system, and Al₂O₃ grains in the MgF₂-Al₂O₃ system were observed by optical microscopy.     

Systems of Na-Fe-SiO2 Glasses and Steel: I, Wetting and Adherence

Wetting behavior of molten Na₂O-Fe₂O₃-SiO₂ and Na₂O-FeO-SiO₂ glasses on very-low-carbon steel at 900°C in purified Ar was studied. The steel surface was dry-polished and cleaned by ion bombardment. Glass frit was then placed on the metal, and the system was introduced into the furnace without exposure to air. Dynamic advancing and receding contact angles were measured. Shear (push-off) tests were performed on the glass-steel composite at room temperature to determine adherence. The equilibrium contact angles were obtained from the arithmetic mean of the final advancing and receding angles. As the Fe oxide content of the glasses increased, the degree of wetting improved; Fe³⁺ was more effective than a combination of Fe³⁺ and Fe²⁺ in improving the wettability. Glasses very nearly saturated with Fe oxide exhibited high adherence values and chemically adhered to steel.     

Preparation and Cu+-Ion-Conducting Properties of the Glasses in the System CuBr–Cu2MoO4–Cu3PO4

Cu⁺-ion-conducting glasses were prepared in the pseudoternary system CuBr–Cu₂MoO₄–Cu₃PO₄, and the ion-conducting properties of the glasses obtained were compared to those of the glasses in the system CuI—Cu₂MoO₄—Cu₃PO₄, which contain CuI instead of CuBr. The CuBr—Cu₂MoO₄—Cu₃PO₄ glasses showed high ion conductivities in the range of 10⁰ to 10⁻² S · m⁻¹ at room temperature. The change in ion-conducting properties caused by the substitution of PO^3-₄ anions for MoO²⁻₄ anions was larger than the change caused by the substitution of Br⁻ anions for I⁻ anions in the glasses containing a constant amount of the cuprous halides.     

Populations and Emission Properties of the 5I6 and 5I7 Levels in Ho3+ Doped into PbO–Bi2O3–Ga2O3 Glasses

Emission properties of PbO–Bi₂O₃–Ga₂O₃ glasses doped with Ho³⁺ were investigated for fiber-optic amplification at the 1.18 μm wavelength region. When the glasses were doped with Ho³⁺ ions only, there was a weak emission at 1.18 μm with a lifetime of ∼200 μs. However, when Yb³⁺ ions were codoped, the lifetime of the 1.18 μm emission increased to 630 μs together with a significant increase in intensity. A similar enhancement in the intensity and lifetimes was realized for the 2.05 μm emission. These effects are due to energy transfer from the Yb³⁺:²F_5/2 to the Ho³⁺:⁵I₆ level. Devitrification of the ternary PbO–Bi₂O₃–Ga₂O₃ glasses was efficiently suppressed by adding 10 mol% GeO₂. Optimum Ho³⁺ concentration was ∼0.4 mol%, whereas Yb³⁺ ions can be added up to the solubility limit.     

Characterization and Microwave Dielectric Properties of M2+Nb2O6 Ceramics

This paper details the investigation of the quality factor ( Q ), dielectric permittivity (ɛ_r) and temperature coefficient of resonant frequency (τ_f) of the TE_01δ mode of the columbite binary niobate ceramics, with the formula MNb₂O₆ where M=²⁺ cation, in relation to their degree of sintering, microstructure and phase composition. The ceramics were made from a mixed oxide preparative route and fired over a range of temperatures from 800° to 1400°C, and most formed the columbite structure. A comprehensive study was made of the niobates containing the transition metal cations M=Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺, and the group II metal cations M=Mg²⁺, Ca²⁺, Sr²⁺, and Ba²⁺. All columbite niobates were found to have ɛ_r between 17 and 22 and negative τ_f values between –45 and –76 ppm/°C, and ZnNb₂O₆, MgNb₂O₆, CaNb₂O₆, and CoNb₂O₆ had high Q f values of 84 500, 79 600, 49 600, and 41 700 GHz, respectively. The Q f of MgNb₂O₆ was found to rise to over 95 000 GHz when heated at 1300°C for 50 h.     

Effects of M3+ Ions on the Conductivity of Glasses and Glass-Ceramics in the System Li2O—M2O3—GeO2—P2O5 (M = Al, Ga, Y, Dy, Gd, and La)

Glasses with compositions Li_1.2M_0.2Ge_1.8(PO₄)₃ (M = Al, Ga, Y, Gd, Dy, and La) were prepared and converted to glass-ceramics by heat treatment. The effects of the M³⁺ ions on the conductivity of the glasses and glass-ceramics were studied. The main phase present in the glass-ceramics was the conductive phase LiGe₂(PO₄)₃. Al³⁺ and Ga³⁺ ions entered the LiGe₂(PO₄)₃ structure by replacing Ge⁴⁺ ions, but lanthanide ions did not. The glass-ceramics exhibited much higher conductivity than the glasses. With increased ionic radius of the M³⁺ ions, the conductivity remained almost unchanged at ∼3 × 10⁻¹² S/cm for the glasses, but it decreased from 1.5 × 10⁻⁵ to 8 × 10⁻⁹ S/cm for the glass-ceramics at room temperature. The higher conductivity for Al³⁺- and Ga³⁺-containing glass-ceramics was suggested to result from the substitutions of Al³⁺ and Ga³⁺ ions for Ge⁴⁺ ions in the LiGe₂(PO₄)₃ structure.