The optical properties of some borate glasses

The optical properties of potassium borate and sodium borate glasses are presented. The fundamental absorption edge for all the series of glasses were analysed in terms of the theory of Davis and Mott. The position of absorption edge and hence the value of the optical gap, was found to depend on the semiconducting glass composition, and the absorption in these glasses is believed to be associated with indirect transitions. The infrared spectra were recorded and appeared individually similar, which is consistent with the absence of significant structural change between the various glass specimens.     

Effect of composition on valence states of iron cations in some borate glasses

We present the results of magnetic studies and Mössbauer effect measurements on 20Fe₂O₃80[3B₂O₃(1?x)PbOxA_uO_v] glasses with A_uO_v = CaO, As₂O₃ or GeO₂. The fraction r of ferrous ions is not dependent on CaO content, while in case of glasses with As₂O₃ and GeO₂ a linear variation is observed. The increase of the number of ferric ions is proportional to the difference between the valences of A ions and that of lead as well as on A_uO_v content. The magnetic measurements show that the reciprocal susceptibility for T ? 50 K has a nonlinear variation, typical for systems with random distribution of exchange interactions. At T > 50 K, a Curie-Weiss behaviour is evidenced. The Curie constants show a composition dependence similar to that of r values. Finally, the influence of the glass matrix composition on the iron valence states is discussed.     

Impact of graphite impurities on the structure and optical properties of the sodium borate oxide glass

For the carbon-based glass fabrication/manufacture process, different amounts of pure graphite powder were added up to 100 wt.% of sodium tetraborate oxide (the weight of one mole of the sodium tetraborate is 381.372 g/mol) and then melted at 950 °C for 2 h before fast quenching in the air at RT. The resulted solids were examined by the XRD and SEM techniques, which confirmed the amorphous natures for studied samples. FTIR spectroscopy showed that some C-atoms are shared in the glass network as C–O and CO₂. In contrast, the UV–Vis showed that the increase in the graphite contents/impurities causes a red shift in the value of the optical edge and the value of Fermi energy. Also, the increase of the graphite impurities causes a decrease in the bandgap values of both direct and indirect electronic transitions. Both the values of Urbach energy and the metallization indicated an increase in the crystallinity degree as the graphite content increase. A graphite-based glass is a promising material for wide-scale applications.

     

Ultrasonic study and physical properties of some borate glasses

The structure of the glass system (75−x)B₂O₃–xBi₂O₃–25Li₂O, where x=5, 10, 15, and 20 mol% was investigated by using pulse-echo technique. Elastic properties of the glass system have been calculated together with Poisson’s ratio and Debye temperature from the measured densities as well as longitudinal and shear ultrasonic velocities at room temperature. Ultrasonic velocity measurements were taken at 4 MHz. Estimated parameters based on Makishima–Mackenzie theory and bond compression model were calculated in order to analyse the experimental elastic moduli. Addition effect of Bi₂O₃ on the elastic moduli was investigated in terms of the number of network bonds and the mean cross-link density of the glass systems. The average atomic ring size of the network was also calculated and it was found that it depends on the concentration of the modifiers. Composition dependence of the elastic moduli and Poisson’s ratio from one hand and the trend of both the ring diameter and the packing density from the other hand showed structural change at x=15 mol%.     

Ultrasonic investigation and infrared absorption of some sodium borate glasses

Ultrasonic velocities and absorption measurements in sodium borate glasses containing Na₂O have been made using the pulse echo technique at 4, 5 and 6 MHz. Results showed an increase in velocity as the sodium oxide content (mol%) increased. The ultrasonic absorption results showed the presence of very high and well-defined peak which shifts its position to lower temperatures with increasing frequency. This suggests some sort of relaxation process and the activation energy of this process increased with increasing Na₂O concentration (mol%). The infrared absorption spectra of sodium borate glasses confirmed the results obtained by ultrasonic investigations.     

The preparation and properties of some lithium borate based glasses

The preparation and properties of lithium borate based glasses are described. The properties which were monitored included the glass-forming ability, the thermal stability, the chemical durability and the mechanical behaviour. Methods which were used in an attempt to improve the mechanical properties of these glasses are also discussed, including controlled crystallization, chemical ion-exchange and fibre reinforcement. The strongest glass, which had a mean strength of ~ 280 MPa in biaxial flexure, was produced by ion-exchange in molten sodium nitrate.     

Structure and physical properties of sodium borate glasses containing nickel oxide

A series of glass samples were prepared from a mixtures of B₂O₃, Na₂O and NiO. The role of nickel oxide in a glass matrix was studied by using infrared spectra, optical absorption, magnetic susceptibility, density, and differential thermal analysis (DTA). It was shown that the addition of nickel oxide at different concentrations to the glass batches causes some deformation in the glass structure. The values of ligand field strength and Racah parameter indicated an increasing degree of covalency. The glass samples exhibited diamagnetic behaviour with NiO content up to 1 g, then paramagnetic behaviour. The densities and glass transition temperatures decreased with increase in the NiO content up to 0.2 g and then increased again. This tendency may be related to changes in the glass structure.     

Effect of PbO layers with nickel oxide and vanadium oxide additions on the thermal oxidation of InP

IR and ultrasoft x-ray emission spectroscopy data indicate that the thermal oxidation of PbO/InP structures with additions of transition-metal (nickel and vanadium) oxides leads to the formation of multicomponent layers consisting of nickel, vanadium, lead, and indium phosphates. These oxide additions to PbO nanolayers accelerate the thermal oxidation of InP. A small amount of vanadium oxide added to PbO gives rise to a significant contribution of a catalytic mechanism to the accelerated thermal oxidation of InP. The principal distinction between the PbO/InP and (PbO + NiO)/InP structures is that the thermal oxidation of the latter leads to the formation of an In_xNi_yP_z transition layer, which influences the growth rate and the composition of the resulting layer.     

Physical,optical and structural studies of copper-doped lead oxychloro borate glasses

Bluish coloured glasses are obtained from the composition PbCl\(_{2}\)–PbO–B\(_{2}\)O\(_{3}\) doped with Cu\(^{2+}\) ions. Basic physical properties and spectroscopic studies (optical absorption, electron paramagnetic resonance, Fourier transform infrared and Raman spectroscopies) were carried out on these samples. The increase in PbCl\(_{2}\) content resulted in the decrease in density and increase in molar volume. At optical frequencies, band gaps and Urbach energies were evaluated and their variation is explained. Spin-Hamiltonian parameters (SHP) obtained from the EPR spectra suggest that the ligand environment around Cu\(^{2+}\) is tetragonally distorted octahedral sites and the orbital \(d_{x^{2}-{y}^{2}} \) is the ground state. The characteristics broad bands in the optical absorption spectra are assigned to the \(^{2}\)B\(_{\mathrm{1g}}\,\rightarrow \, {}^{2}\)B\(_{\mathrm{2g}}\) transition. The bonding coefficient values were evaluated using optical data and SHP. FTIR studies suggested that the glass structure is built up of BO\(_{3}\) and BO\(_{4}\) units. The presence of diborate, pyroborate, pentaborate groups, etc. in the glass network was confirmed from Raman spectra.     

Structure and magnetic susceptibility of irradiated sodium borate glasses containing nickel oxide

The effect of introducing soda to boric oxide on the optical absorption infrared spectra and magnetic susceptibility of sodium borate glass system containing nickel oxide was studied. It was found that increasing of Na₂O helps in forming the BO₄ group and nonbridging oxygen and the nickel ions change from the octahedral state to the tetrahedral state. The magnetic susceptibility also increases rapidly with gradual increase of soda content up to 20 mol%, and then slightly increases, this may be due to the change in the coordination number of nickel ions. Also the effect of the addition of nickel oxide was studied, it was found that the values of magnetic susceptibility increases with the gradual increase of the nickel oxide, which is due to the increase of Ni²⁺ in octahedral coordination.     

Raman spectroscopic study of hexavalent chromium in some silicate and borate glasses

The polarized Raman spectra of chromium-doped silicate and borate glasses have been measured and interpreted. It is shown that hexavalent chromium exists in silicate glasses as isolated chromate anions (CrO₄⁼). In binary sodium borate glasses there is a change of species from chromate to dichromate as the B₂O₃ concentration is increased.     

Structural and thermal properties of some zinc borate glasses containing gadolinium ions

Glasses in the system (Gd₂O₃)_x·(B₂O₃)_(60−x)·(ZnO)₄₀ (0 ≤ × ≤ 15 mol%) have been prepared by the melt-quenching technique. The local structure and the thermal behaviour of the obtained glasses were investigated using X-ray diffraction (XRD), differential thermal analysis (DTA) and Fourier transform infrared (FTIR) spectroscopy. The XRD pattern of the glasses confirmed their amorphous nature. Compositional dependence of the glass transition (T_g), fragility index (F), activation energy of the glass transition (E_g), activation energy for the crystallization process (E_p) were determined by DTA investigations. FTIR data revealed that the short-range order of glasses is affected by the addition of the Gd₂O₃ to the host glass matrix. The compositional dependence of the different structural units which appear in the investigated glasses was followed. FTIR data suggest that the gadolinium ions play the network modifier role in the studied glasses.     

Effect of growth temperature on structure and optical characters of NiO films fabricated by PA-MOCVD

We report the effect of growth temperature on structure, optical and electrical properties of NiO films fabricated by Photo-assisted Metal Organic Chemical Vapor Deposition (PA-MOCVD). It is found that the crystal quality of the NiO films has been improved by increasing the growth temperature. When the temperature is low, the NiO film is composed of small and anomalous grains, whereas the film is composed of grains with a cubic shape following the NaCl-type structure when the temperature is higher. The samples marked A-D under the growth temperature of 510, 540, 570 and 600 °C have optical band gap values of 3.93 eV, 3.82 eV, 3.73 eV and 3.55 eV, respectively. Comparatively, the controllable electrical properties of the films can be achieved by the variation of crystal quality arises from the growth temperature.     

Optical properties of Ce-doped oxide glasses and correlations with optical basicity

A series of Ce³⁺-doped phosphate, borate, silicate and germanate glasses were prepared and their optical properties were investigated. Experimental observations on transmission and photoluminescence spectra show obvious Nephelauxetic effect depending on the optical basicity of glasses. Especially, addition of alkaline earth oxides as a substitution of glass network former contributes to the further red shifts of excitation and emission bands due to increases in the number of less polarized non-bridging oxygen ions which increase the optical basicity of the system.     

Effect of oxide dopant on the structure of fluorozirconate glasses studied by X-ray photoelectron spectroscopy

The effect of oxide dopant on the structure of 62ZrF₄-30BaF₂-8LaF₃ (mol%) glass by equimolar substitution of BaO for BaF₂ was studied by X-ray photoelectron spectroscopy (XPS). The XPS spectra of La 3d, Ba 3d, F 1s, O 1s and Zr 3d were measured. From the deconvoluted results for the XPS spectra of elements in the glass, it was proposed that the oxide ions added to the glass mainly bond to Zr⁴⁺ and replace the bridging fluoride ions resulting in the formation of the F-Zr-O bond. Further analyses indicated that the oxide ions mainly play a non-bridging role instead of a bridging role in the glass structure.