The results and detailed discussion of an extensive experimental study of infrared spectra of the x (PbO)-(1−x)P2O5 vitreous system (x=0.3–0.75) together with a brief review of infrared spectra of phosphate compounds, are presented. Theoretical models employed in the interpretation of infrared spectra of glasses have been reviewed. The frequency ranges of various infrared bands belonging to PO
 4
 3−
 and P2O
 7
 4−
 , observed in different phosphate compounds, are discussed. The glassy and quenched samples were prepared from PbO and NH4H2PO4 by the rapid quenching technique. The infrared spectra of the constituents of the system, PbO and P2O5, in their polycrystalline and glassy forms, have been discussed. The intensity and wavenumbers of the infrared bands around 1600 and 3300 cm−1, assigned to the bending and stretching modes in H2O trapped by the hygroscopic glasses, have been followed for different compositions with x<0.5. The changes observed in these infrared bands established the role of water as an additional glass modifier. The intensity and frequency variations of the infrared bands have been followed through all the compositions for characteristic phosphate group frequencies including P=O, P-O-P stretching and bending modes and P-O bending mode. The results clearly suggest that the x(PbO)-(1−x)P2O5 system undergoes gradual structural changes from metaphosphate (x=0.5), to pyrophosphate (x=0.66) and to orthophosphate (x=0.75). The continuing presence of the infrared band, in varying intensity, in the region 1200–1280 cm−1 attributed to P=O, suggests that the glass-forming ability of the binary system is extendable at least up to x=0.66 composition, and that no complete rupture of P=O bond by Pb2+ takes place. The ionic character of the phosphate groups, P-O(−), PO
 4
 3−
 is well revealed by significant changes with the PbO content in the spectral features of the infrared bands around 1120 and 980 cm−1 respectively. The maximum intensity of the P-O(−) band at 1120 cm−1 for 55 mol% PbO suggests a partial breakdown of the covalent vitreous network of the phosphates and formation of a crystalline phase consisting of ionic groups PO
 4
 3−
 , P2O
 6
 2−
 and P2O
 7
 4−
 for PbO greater than 55 mol%. The observed pattern of variation in the intensity of the infrared bands in the 940–1080 cm−1 region attributed to the v3-mode in PO
 4
 3−
 , suggests a gradual transformation of PO
 4
 3−
 units to PO
 3
 −
 groups in lead meta-phosphate glass and then their restoration to PO
 4
 3−
 groups of pyro- and ortho-phosphate quenched samples. The results indicate a gradual decrease in the number of bridging oxygens and increase in the resonance behaviour of non-bridging oxygens as the mole percentage of metal oxide (PbO) increases in the glass. The infrared spectra of several binary phosphate glasses have been reviewed in the context of the study of effect of the cation on the infrared spectra. It is found that the influence of the cation on the infrared spectra of phosphate glasses does not show any striking regularity. Theoretical calculations of these band frequencies were found to agree well only in the case of pure stretching (P=O and O-H) vibrations and pure bending (P-O-P and O-H) vibrations. The disagreement in the case of P-O(−), P-O-H and other modes of P-O-P groups, has been attributed to the mixed nature of modes occurring in glasses. The changes in the positions of the characteristic bands and their relative intensities are strongly dependent on the structural units and PbO content in the phosphate glasses and the results emphasize the role of PbO as a network modifier.

Structural investigations of phosphate glasses: a detailed infrared study of the x(PbO)-(1−x) P2O5 vitreous system

Spectroscopic studies of Nd3+-doped alkali fluoroborophosphate glasses

IR and UV spectral studies for rare earths-doped tellurite glasses

This paper reports on different physical and optical properties of Nd3+-doped bismuth borate glasses. The glasses containing Nd3+ in (25 - x)Bi2O3:20Li2O:20ZnO:35B2O3:xNd2O3 (where x = 1, 1.5, 2 mol%) have been prepared by melt-quenching method. The amorphous nature of the glasses was confirmed by X-ray diffraction studies. The physical parameters like dielectric constant, refractive index, ionic concentration, oxygen-packing density, inter ionic distance, polaronradius, reflection loss, energy gap, molar refractivity, molar polarizability, electronic polarizability, optical basicity and field strength are computed. On the basis of the measured values of the density and refractive index, the Nd3+ ion concentration in glasses, the polarizability of oxide ions and optical basicity were theoretically determined. The theoretical value of average electronic polarizability and oxide ion polarizability were calculated by using Lorentz-Lorenz formula. Theoretical optical basicity of the glasses is evaluated based on equation proposed by Duffy and Ingram. The metallization criterion has also been calculated on the basis of refractive index and energy gap. The large value of metallization criterion indicates that the glass materials are insulators. The results obtained predict the nature of bonding in the present glasses and provide basis for developing new nonlinear optical material.

/pdf/optical-basicity-and-polarizability-of-nd-3-doped-bismuth-dvgq6262ll.pdf

Optical Basicity and Polarizability of Nd 3+ -Doped Bismuth Borate Glasses

Improving and accelerating bone repair still are partially unmet needs in bone regenerative therapies. In this regard, strontium (Sr)-containing bioactive glasses (BGs) are highly-promising materials to tackle this challenge. The positive impacts of Sr on the osteogenesis makes it routinely used in the form of strontium ranelate (SR) in the clinical setting, especially for patients suffering from osteoporosis. Therefore, a large number of silicate-, borate-, and phosphate-based BGs doped with Sr and produced in different shapes have been developed and characterized, in order to be used in the most advanced therapeutic strategies designed for the management of bone defects and injuries. Although the influence of Sr incorporation in the glass is debated regarding the obtained physicochemical and mechanical properties, the biological improvements have been found to be substantial both in vitro and in vivo. In the present study, we provide a comprehensive overview of Sr-containing glasses along with the current state of their clinical use. For this purpose, different types of Sr-doped BG systems are described, including composites, coatings and porous scaffolds, and their applications are discussed in the light of existing experimental data along with the significant challenges ahead.

/pdf/multiple-and-promising-applications-of-strontium-sr-35qa9hbhmb.pdf

Multiple and Promising Applications of Strontium (Sr)-Containing Bioactive Glasses in Bone Tissue Engineering.

Results of measurements of the dc electrical conductivity, optical absorption edge and infrared optical absorption of GeO2-TeO2 glasses are reported Conduction in these glasses is found to be electronic and the hopping of polarons seems to be the dominant process in the transport mechanism The electrical activation energy decreases with the increase of tellurium content and this decrease corresponds to a decrease in the optical energy gap The optical gap is of the order of 274 eV, somewhat lower than for many other oxide based glasses Most of the sharp absorption bands characteristic of the basic materials GeO2 and TeO2 are modified with the formation of broad and strong absorption bands in the process of going from the crystalline to the amorphous state Density measurements show the glasses to have a compact structure

A study of the electrical and optical properties of the GeO2-TeO2 glass system

The physical parameters such as density, X-ray diffraction, infra-red absorption spectra and optical absorption measurements are discussed with respect to all compositions. The d.c. conductivity was measured for semi-conducting vanadium phosphate glasses containing 5 mol% rare-earth oxides. The conductivity of vanadium phosphate glasses is slightly higher than the corresponding compositions with rare-earth oxides. The heat treatment in the range 300 to 500° C caused progressive microstructural changes which dramatically affected the electronic conductivity (σ) and the activation energy for conduction (W). It was also found that the incorporation of rare-earth oxides did not affect the limits of the ultra-violet absorption edge of the base glass.

M. N. Khan

Papers

A study of the electrical and optical properties of the GeO2-TeO2 glass system

A comparative study of the effects of rare-earth oxides on the physical, optical, electrical and structural properties of vanadium phosphate glasses

The effect of temperature on the optical absorption edge of germanium vanadate glass