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The main objective of the study is to investigate the influence of therapeutically active vanadium ions on the in vitro bio-active properties of calcium oxy fluoro borophosphate glasses mixed with different modifier oxides viz ., BaO, SrO, ZnO and MgO. The investigations mainly include the degradation studies of the chosen glasses in simulated body fluid (SBF) for a prolonged period (about 800 h). The rate of degradation was estimated by measuring the weight loss of the samples and by measuring the pH of the residual SBF solution at regular intervals of immersion time. During the immersion of the samples in SBF solution, a thin layer of crystalline hydroxy apatite layer (HAp) is observed to develop on the surface of the glass samples. The comparison of the results of XRD, SEM, EDS and IR spectral studies of pre and post immersed samples confirmed the formation of HAp layer embedded with calcium vanadate crystal phases. From the XRD studies it is understood that the magnitude of HAp layer developed on the surface of the samples is the highest for BaO modifier mixed glasses. The optical absorption as well as EPR spectral studies of pre and post immersed samples confirmed that vanadium ions existed in different oxidation states, mainly in V 4+ and V 5+ states, in the bulk glass samples. The ratio of the concentration of these two ions is predicted to be different for different modifier oxides mixed glasses and such variation is predicted to play a vital role in the variations of the magnitude of HAp layer formed on the surface of the samples. The bioactivity of the samples is estimated from the qualitative information on the magnitude of HAp layer formed on the surface of the samples and also the degradability of the samples in SBF solution which is estimated by measuring weight loss as well as pH of the residual SBF. The overall analysis of the results of in vitro bioactivity studies (degradability studies together with spectroscopic studies) revealed that among various glasses mixed with different modifier oxides, the glass mixed with BaO is found to be the superior bioactive material. Such glasses may be useful in improving the osteogenic activity in the human body if used as bone implants since it contains HAp layer embedded with calcium vanadate crystal phases. However quantitative in vitro cell culture studies are required to establish this. [ABSTRACT FROM AUTHOR]

[(PbO)0.20-x(Bi2O3)0.40(B2O3)0.40]:(TiO2) x, 0.0 ≤ x ≤ 0.02 glasses were prepared. Dielectric properties (dielectric constant ε', loss tan δ and a.c., conductivity σac, over a wide range of frequency and temperature), optical absorption, ESR and IR spectra of these glass materials have been investigated. The dielectric study has revealed that the glasses possess high insulating strength when TiO2 concentration is >0.8 mol% in the glass matrix. The optical absorption spectra of these glasses exhibited bands due to Ti³+ ions in the visible region. ESR spectral studies have also indicated that a fraction of Ti4+ ions reduced to Ti³+ ions. IR spectra of these glasses exhibited bands due to TiO4 and TiO6 structural units. Quantitative studies indicate that as concentration of TiO2 is increased to 0.8 mol% in the glass matrix, a large proportion of titanium ions exist in Ti3+ state and has influenced the physical properties of these glasses to a substantial extent. [ABSTRACT FROM AUTHOR]

[(PbO)0.20-x(Bi2O3)0.40(B2O3)0.40]:(TiO2) x, 0.0 ≤ x ≤ 0.02 glasses were prepared. Dielectric properties (dielectric constant ε', loss tan δ and a.c., conductivity σac, over a wide range of frequency and temperature), optical absorption, ESR and IR spectra of these glass materials have been investigated. The dielectric study has revealed that the glasses possess high insulating strength when TiO2 concentration is >0.8 mol% in the glass matrix. The optical absorption spectra of these glasses exhibited bands due to Ti³+ ions in the visible region. ESR spectral studies have also indicated that a fraction of Ti4+ ions reduced to Ti³+ ions. IR spectra of these glasses exhibited bands due to TiO4 and TiO6 structural units. Quantitative studies indicate that as concentration of TiO2 is increased to 0.8 mol% in the glass matrix, a large proportion of titanium ions exist in Ti3+ state and has influenced the physical properties of these glasses to a substantial extent. [ABSTRACT FROM AUTHOR]

The objective of this study is to investigate the principal role of Y 2 O 3 , Sc 2 O 3 and HfO 2 on the enhancement of 1.06 μm emission beam of Nd 3+ ion in PbO–Sb 2 O 3 glass system. The emission spectrum of Nd 3+ doped glass exhibited emission bands at 900, 1060 and 1335 nm. When the glasses are co-doped with Y 2 O 3 , Sc 2 O 3 and HfO 2 and excited at 528 nm, a substantial hike in the intensity of 1060 nm emission band is observed. The comparison of luminescence efficiency of Nd 3+ ion of the glasses mixed with three co-dopants indicated the highest enhancement in the intensity of this emission in the glass co-doped HfO 2 . The reasons for such enhancement have been discussed in the light of varying environment of the glass network in the vicinity of Nd 3+ rare earth ions. [ABSTRACT FROM AUTHOR]

P 2 O 5 PbO Bi 2 O 3 R 2 O 3 (R = Al, Ga, In) glasses doped with Dy 2 O 3 were prepared by melt quenching technique. The prepared glasses were characterized by XRD, optical absorption, FTIR, luminescence studies. Judd-Ofelt parameters have been evaluated for three glass systems from optical absorption spectra and in turn radiative parameters for excited luminescent levels of Dy 3+ ion are also calculated. Emission cross section and branching ratio values are observed to high for 6 H 13/2 level for Dy 3+ ion. The yellow to blue intensity ratios and CIE chromaticity coordinates were calculated. Decay curves exhibit non exponential behavior. Quantum efficiency of prepared glasses was measured by using radiative and calculated life times. IR studies, J-O parameters and Y/B ratio values indicate that more asymmetry around Dy 3+ ions in Ga 2 O 3 mixed glass was observed. Chromaticity coordinates lie near ideal white light region. These coordinates and CCT values have revealed that all the prepared glasses emit quality white light especially the glasses mixed with Ga 2 O 3 are suitable for development of white LEDs. [ABSTRACT FROM AUTHOR]

Calcium oxy fluoro boro phosphate glasses with fixed concentration of CuO and mixed with different modifier oxides (viz., BaO, SrO, ZnO and MgO) that play a vital role in collagen deposition, cellular activity, proliferation of osteoblasts and in blood vessel maturation, producing enzymes etc., that are necessary for normal functioning of human body were synthesized. In vitro bioactivity studies indicated the formation of hydroxy apatite (HAp) layer on the surface of the samples. This was confirmed by XRD and SEM photographs and also IR spectral studies. The magnitude of HAp layer formed was evaluated by measuring weight loss of the samples and pH measurements of the residual simulated body fluid (SBF) solutions at specific intervals of time. The analysis of the results of degradability studies together with spectroscopic studies has revealed that BaO is an effective modifier in improving the bioactivity of the host glass, among all the modifiers investigated. [ABSTRACT FROM AUTHOR]

Lead silicate glasses mixed with 5.0 mol% of Bi 2 O 3 and doped with varying concentrations of CoO have been synthesized. Optical absorption, infrared and photoluminescence spectra and luminescence decay profiles of the prepared glasses were recorded at ambient temperature. Analysis of IR spectral results have indicated that there is increasing proportion of the tetrahedral Co 2+ ions in the glass network with increase in the concentration of CoO. The emission spectra of Bi 2 O 3 free glasses exhibited two significant bands in the orange and red regions when excited at 595 nm. These bands are identified as being due to 4 T 1 ( 4 P)→ 4 A 2 ( 4 F) and 4 T 1 ( 4 P) → 4 T 2 ( 4 F) tetrahedral transitions of Co 2+ ion, respectively. The intensity of orange emission band due to 4 T 1 ( 4 P)→ 4 A 2 ( 4 F) transition is found to be enhanced nearly five times when the glasses are mixed with 5.0 mol% of Bi 2 O 3 . The quantitative analysis of these results indicated that the energy transfer from 3 P 1 → 1 S 0 emission transition of Bi 3+ ions to 4 T 1 ( 4 P)→ 4 A 2 ( 4 F) tetrahedral transition of Co 2+ ion is responsible for the enrichment of this orange emission. [ABSTRACT FROM AUTHOR]

The transparent glasses with composition 30PbO–10GeO 2 –(60−x)SiO 2 −xNb 2 O 5 (mol%) (0 ≤ x ≤ 2.5) are prepared by conventional melt quenching technique. The amorphous nature of the prepared glasses is characterized by XRD. The spectroscopic studies such as optical absorption, FTIR, Raman spectra were carried out at room temperature on these glasses. Besides this electrical properties, like dielectric constant ε ' , loss tan δ , ac conductivity σ a c etc., were also investigated over a moderately wide range of frequency (10 3 –10 6 Hz) and temperature (30–300 °C). The optical absorption spectrum of the prepared glasses has exhibited absorption bands around 325 nm and 340 nm and these are due to the triplet – singlet electronic transition of Ge 2+ state presents in the glass matrix as conversion of GeO 2 into GeO is much easier rather than SiO 2 . From FTIR spectra of as prepared glasses, it is noticed that the intensity of octahedral NbO 6 structural units is found to increase up to 2 mol% of Nb 2 O 5 there after it is observed to decrease. It is also supported by Raman shift of NbO 6 structural units observed around 650 and 930 cm −1 . The analysis of electrical studies is also revealed that the conductivity of prepared glasses is found to increase gradually up to 2 mol% of Nb 2 O 5 beyond this concentration it is observed to decrease. When the spectroscopic investigations are coupled with electrical studies it is concluded that the glass samples doped with 2 mol% of Nb 2 O 5 are found to exhibit good semiconducting nature among the prepared glasses. Such glasses are suitable for fabrication of solid state devices. [ABSTRACT FROM AUTHOR]

Abstract: Na2SO4–BaO–P2O5 glasses doped with different concentrations of Fe2O3 were prepared. The valence states of iron ions and their coordination in the glass network have been investigated using optical absorption, ESR, IR and Raman spectroscopy. Electrical and dielectric spectral features have been studied over a wide frequency range (10−2–106 Hz) and within the temperature range from 303 to 523K. The ac and dc conductivities have exhibited maximal effect, whereas the activation energy for the conductivity demonstrated minimum at 1.5mol% of Fe2O3. The ac conductivity in the low temperature region is explained based on quantum mechanical tunneling (QMT) model. The analysis of the dc conductivity indicated that at T>θD/2, the small polaron hopping model is appropriate. The dispersion of real part of dielectric constant ε′(ω), and loss, tan δ, with temperature have been analyzed quantitatively on the basis of space charge and orientation polarization models. [Copyright &y& Elsevier]

Abstract: LiI–AgI–B2O3 glasses mixed with different concentrations of V2O5 (ranging from 0 to 1.0mol%) were prepared. Electrical and dielectric properties over wide ranges of frequency (10−2–107 Hz) and temperature (173–523K) have been studied. Additionally spectroscopic properties viz., optical absorption and ESR spectra have been investigated. The optical absorption and ESR studies have revealed that vanadium ions do exist in both V4+ and V5+ states and the redox ratio is the highest in the glasses containing 0.8mol% of V2O5. The results of conductivity measurements have indicated that there is a mixed conduction (both ionic and electronic). The ionic conduction seems to be dominant over polaron hopping only in the glasses containing V2O5 more than 0.8mol% of V2O5. The impedance spectra have also indicated that the conduction is predominantly polaronic in nature. The frequency and temperature dependence of the electrical moduli as well as dielectric loss parameters have exhibited relaxation character attributed to the vanadyl complexes. The relaxation effects have been analyzed by the graphical method and from this analysis it has been established that there is a spreading of relaxation times. The results have been further discussed quantitatively in the light of different valance states of vanadium ions with the aid of the data on spectroscopic properties. [Copyright &y& Elsevier]