Barium Borate Glasses Research Articles

Infrared study of the effect of heat treatment and irradiation on barium borate glass containing iron

A barium borate glass system was prepared containing different amounts of iron. The prepared glasses were heat treated at 550° C for 2, 6, 12, 18 and 24 h. Also the glasses were irradiated usingψ-ray at a dose of 4.805 × 104rad h−1 for 12, 18 and 24 h. The infrared spectra were recorded for the untreated and heat treated samples. It was found that, when the Fe2O3 was introduced in the glass the triangle BO3 groups were transferred to BO4 groups. The formation of non-bridging oxygen with high concentration was also observed as a result of introducing Fe2O3 in the glass. The absorption bands of the IR spectra of the irradiated samples indicated no significant variations, and only a transfer of some BO4 groups to BO3 groups could be observed.

Energy transfer from Tm 3+ to Pr 3+ in barium borate glass

The system of Tm 3+ and Pr 3+ in barium borate glass is investigated for finding out the mechanism of nonradiative energy transfer at room temperature. The various constants for this system relevant to the energy transfer are also calculated.

Thermal properties of barium-borate glass containing iron in the temperature interval 300 to 700K

The study of thermophysical properties of glasses containing transition metal oxide has received lately more attention. Glasses containing iron oxide were studied by Avogadro et aI. [1 ], Kinser [2], Mackenzie [3] and others [41 . The major objective of this work is to study the effect of composition and temperature on the thermal properties of barium-borate glasses containing different iron concentrations. Generally the thermal properties of glasses containing transition metal oxides were hardly studied. A homogeneous mixture of pure chemical powders was melted in an electric furnace at 1100 -+ 20 ° C for 2 h and then quenched in air to prepare a glass system according to the molar formula 75mo1% B203-(25-x) mol% BaOxmol% F%O3 where x = 0, 1, 2.5, 7.5 and 10. The samples were crushed into powder and pressed under a pressure of 13toncm -2. Discs ofO.013 m in diameter and 2 x 10-3m in thickness were obtained. For the simultaneous determination of thermal properties (Cp, X, a) a plane temperature waves method was used [5, 6]. The experimental errors of these properties did not exceed 3.5% for the specific heat capacity and thermal conductivity, and 3 to 6% for the thermal diffusivity measurement.

Buildup of the acceptor emission as a result of energy transfer from Tb 3+ to Sm 3+ in barium borate glass

Intensity and lifetime data indicate that the self-quenching of Sm 3+ fluorescence in barium borate glass matrix is by direct dipole-quadrupole interactions. The quenching of Tb 3+ fluorescence by Sm 3+ has been found due to direct dipole-dipole interactions. However, at relatively low Sm 3+ concentrations, energy transfer through migration among Tb 3+ ions also occurs. Further at low Sm 3+ concentrations, there is an enhancement of Sm 3+ emission due to energy transfer to an Sm 3+ that is not coupled to a second Tb 3+ or Sm 3+ ion. At high Sm 3+ concentrations, no enhancement of Sm 3+ emission occurs and is attributed to transfer to Sm 3+Sm 3+ or Sm 3+Tb 3+ couples that take up the energy by simultaneous transitions that lie well below the 4G 5 2 manifold of Sm 3+.

Magnetic properties of barium borate glasses containing nickel micro-granules

The EPR spectra of barium borate glasses containing 0.1, 0.25 and 0.4 wt.% nickel particles respectively have been investigated over the temperature range 77K to 300K. The magnetic susceptibility of these glasses has also been measured between 77K and 700K. Both sets of data indicate the presence of a broad range of transition temperatures below 300K. However, the mean transition temperatures as obtained by the two techniques are different. The results confirm a superparamagnetic behaviour exhibited by the fine nickel particles. The interaction energies between the particles and the transition temperatures have been calculated on the basis of the current model, and the discrepancy of the latter with experimental value is ascribed to the presence of a wide range of particle size.

Electron paramagnetic resonance of Cu 2+ and V 4+ ions in borate glasses

The EPR spectra of Cu 2+ and V 4+ ions have been studied in binary ROB 2O 3 glasses (where R = Ba, Sr, Pb and Zn) and in ternary PbOZnOB 2O 3 glasses. The main results of an EPR study of alkali-borate glasses are briefly reviewed. Three distinct EPR spectra of Cu 2+ ions in barium-borate glasses were observed. The superposition of two EPR spectra of a Cu 2+ ion in glasses containing from 5 to 15 mol.% BaO is attributed to a stable liquid immiscibility in these glasses. The structural similarity of barium- and strontium-borate glasses containing 30–40 mol.% RO is established. It is concluded that non-bridging oxygens appear in these glasses for higher concentrations of a modifier than in alkali-borate glasses. The data for Cu 2+ ions in PbOB 2O 3 glasses containing from 20 to 40 mol.% PbO suggest a modifying role for Pb 2+ at such PbO concentrations. Very marked differences between the spectral parameters of low- and high-lead borate glasses are found for a V 4+ ion. The superposition of two distinct EPR spectra of V 4+ ions in binary ZnOB 2O 3 glasses is observed and is attributed to the two-phase structure of these glasses. The structural roles of Pb 2+ and Zn 2+ in ternary PbOZnOB 2O 3 glasses are discussed. The tendency of the Cu 2+ ion to be localized far from lead and zinc ions playing the roles of network formers is established. The high sensitivity of the V 4+ EPR spectra to the main structural units is suggested.

Optical and ESR investigation of borate glasses containing single and mixed transition metal oxides

The optical and electron spin resonance (ESR) spectra of barium borate glasses, containing the oxides of V, Fe and Cu separately and in mixed proportions, have been studied. The optical spectra of the single transition metal (TM) oxide glasses showed the usual features, while those for the mixed glasses showed single bands without showing individual features of the single TM oxide glasses. However, the linear plots of optical density against composition revealed the presence of two valence states for each TM element, and this was confirmed by ESR results as well. The ESR spectra of the mixed glasses showed a complicated interaction pattern for two different TM ions, in comparison with those of the glasses containing a single TM ion. For the Fe-V glasses, the progressively vanishing hyperfine structure of the VO2+ complex with increasing addition of iron oxide is discussed in terms of nuclear spin relaxation, cross-relaxation between two spin systems and spin diffusion within the vanadium spin system. The covalency of the VO2+ complex and the number of distorted Fe3+ ions were found to decrease with increasing addition of Fe2O3 replacing V2O5. Similar features were noted for the Cu-V glasses; the spectra of Cu-Fe glass also showed a strong interaction between two different TM ions. It has been suggested that all the possible four valence states (for a given mixed glass) from two different TM elements are present, and that pairing of two different TM ions from two dissimilar TM elements occurs, facilitating the formation of “associates” (e.g. V4+-O-Fe3+).

Composition dependence of Nd3+ homogeneous linewidths in glasses

Optical homogeneous linewidths of the 4F3/2–4I9/2 transition of Nd3+ in oxide and fluoride based glasses are measured for host composition ranging from simple binary to multicomponent glasses. Homogeneous linewidths at 300 K exhibit a broad range of values, varying by approximately a factor of 4. The ratio of homogenous to inhomogeneous linewidth also varies over a broad range, from 0.16 for a sodium barium borate glass to 1.86 for a rubidium phosphate glass. In addition, the homogeneous linewidth is inversely dependent to the ∼2.5 power of the velocity of sound from host to host. This dependence is not predicted by existing theories of the line broadening process.

ESR-detection of immiscibility in K2O-BaO-B2O3 glasses.

The “latent immiscibilities” in the transparent glasses of the compositions xK2O⋅(y-x) BaO⋅(100-y)B2O3 were effectively detected by the ESR of incorporated Cu (II) ions and termed “ESR-immiscibility”, where x and y range from 0 to y and from 5 to 25, respectively. The ESR spectra for some of the ternary glasses which have the compositions within the glass-forming region were found to be approximate overlap of the spectra of the reference glasses, yK2O⋅(100-y)B2O3 and yBaO⋅(100-y)B2O3. Referring to macroscopic immiscibility in barium borate glasses, the ESR-immiscible glass was considered to consist of the three micro-phases with the approximate compositions yK2O⋅(100-y)B2O3, 17 BaO⋅83B2O3 and B2O3. It was found that the amount of K2O needed to eliminate the ESR-immiscibility is nearly ten times as large as that required to make the opalescence disappear. The ESR method was found to enable one to determine the approximate composition of each phase in an ESR-immiscible glass. This immiscibility was also detected by optical absorption of Co (II) ions in these glasses.

Polaronic conduction and spectroscopy of borate glasses containing vanadium

Barium borate glasses containing 0-35 mole% V2O5 were found to be homogeneous. Optical absorption spectra indicated that only V4+ of the lower valence states of vanadium was present. The molar volume data suggested that a change in the structure associated with vanadium ions occurred at around 22% V2O5. ESR spectra showed that a more continuous change occurred in the electron structure associated with the V4+ ions as the V2O5 content was varied. Resistivity and activation energy decreased rapidly with decreasing vanadium-vanadium separation, while, at constant % V2O5, they showed a minimum at V4+/(V4++V5+)=0.45. Thermoelectric power of glasses with 25-30% V2O5 showed very low activation energies, in agreement with a polaron hopping mechanism.

The effect of glass composition on the mean dispersion of barium borate glasses

The mean dispersion has been determined for glasses in the BaOB 2O 3 system containing between 20 and 40 mol% BaO. The results could be plotted as two straight lines intersecting at about 33 mol% BaO. However, statistical analysis of the results shows that a smooth curve could be drawn to fit the results equally well. Other properties, especially molar refractivity, show marked changes in the vicinity of 33 mol% BaO. The results discussed in the light of structural information obtained from NMR studies.

Energy transfer from UO ++2 → Nd 3+ in barium borate glass

Radiative and non-radiative energy transfer from UO ++ 2 to Nd 3+ has been studied in barium borate glass. Probabilities, efficiencies and the mechanism of non-radiative energy transfer were determined from UO ++ 2 fluorescence decay rates. At low acceptor concentrations pair-wise energy transfer involving migration among donors leads to a non-radiative transfer rate which depends linearly on the concentration of Nd 3+. It is decided that resonant radiationless dipole-dipole transfer of energy is the dominant mechanism active in this system. However, the observations of transfer yield for high acceptor concentrations are contrary to those at low acceptor concentrations as evidenced from the P da vs C 2 plot. Hence at high acceptor concentrations, the transfer could happen between a donor ion and two acceptor ions which is consistent with the view of Fong and Diestler.

Energy transfer from UO 22+ → Ho 3+ in borate glass

Energy transfer from UO 2 2+ to Ho 3+ in barium borate glass has been observed. Dipole-dipole transfer mechanism is found to be dominant. Available data on energy transfer suggest that transfer may take place over considerable distances, much larger than the distance associated with dipole-dipole interaction. Probabilities and efficiencies of non-radiative energy transfer were also calculated from uranyl fluorescence decay rates.

Energy transfer mechanism between manganese and neodymium

The mechanism of energy transfer between Mn 2+ → Nd 3+ in barium borate glass has been investigated. The change in emission intensities and lifetimes of Mn 2+ (donor) due to the presence of Nd 3+ (acceptor) are observed. It has been concluded that the mechanism of energy transfer involves a nonradiative resonance process. The electrostatic multiple interaction responsible for the transfer is dipole—dipole in nature.

The Effect of Temperature and Pressure on the Refractive Index of Some Oxide Glasses.

The change in refractive index with temperature has been determined for some oxide glasses from about -200 to 700 °C. The change in refractive index with applied hydrostatic pressure has been determined at room temperature from a pressure of 105 to 108 Pa. All measurements were made using the yellow spectral line of helium. A calcium aluminate glass, an aluminum magnesium phosphate glass, a binary barium borate glass and a multicomponent germanate glass were studied, as were four commercial specimens of fused silica. From the data at room temperature, it has been possible to calculate the change in electronic polarizability with temperature at constant volume. This parameter has been found to be very high for the glasses as compared to crystals, and this agrees with the results of earlier research on silica-based optical glasses. Furthermore, over the entire temperature range, the change of refractive index with temperature is shown to be due predominantly to the temperature dependence at constant volume of the electronic polarizability. The relevance of the data to the molecular scattering of light in glasses is discussed.

Rheological properties of potassium barium borate glasses

Several series of potassium barium borate glasses have been investigated as to their rheological properties. It has been found, that all these glasses show deviations from ‘Newtonian’ behaviour below temperatures corresponding to viscosities of 10 10 poises. The activation energies of viscous flow are linear in both the potassium and barium mole percentages. For the ternary systems the pre-exponential factors of the viscosities do not decrease considerably with increasing metal ion content, contratry to what has been found in binary systems.

Compressibility of Binary Alkaline‐Earth Borate Glasses at High Pressures

Compression data to 10,000 atm. were obtained for a series of barium, strontium, and calcium borate glasses at 21°C. The compressibility was found to be in the order Ba > Sr > Ca at corresponding molar concentrations and was not appreciably affected by pressure in the experimental pressure range. Comparison of data on alkali and alkaline‐earth borate glasses shows that the compressibility at corresponding molar concentrations is smaller in the alkaline‐earth glasses. Numerical comparisons at appropriate compositions show that a large part of the decreased compressibility produced by the alkaline‐earth oxides arises from electrovalent sources.