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Dilute magnetic glasses of formula xFe2O3+(2-x)V2O5+38Li2O + 60P2O5 (where x=0, 0.2, 0.5, 0.7, 1.0, 1.5 and 2.0) are synthesized by melt quench technique. The glassy nature is confirmed by X-ray diffraction. The density is found to increase but the molar volume and optical basicity are found to decrease as the iron content x is gradually increased from 0 to up to 2. The Fourier transform infrared spectra of these glasses show absorption peaks corresponding to P=O, O-P-O-, (P-O-P) symmetric stretching, (P-O-P) asymmetric stretching, and O-P-O group bending vibrations. The magnetic measurements indicate considerable reduction in magnetization of both vanadium and iron containing glasses. A canted-antiferromagnetic pairing of the magnetic ion pairs is envisaged for explaining the reduction of magnetization. The EPR spectra reveal the presence of vanadyl ion and ferric ion in the glasses. Characteristics of local bonding and co-ordination of vanadyl and ferric ions are discussed. The vanadyl ion is shown to have a distorted octahedral coordination with oxygen to create a tetragonal contraction. The high spin ferric ion is concluded to possess two kinds of co-ordinations with oxygen viz. rhombic and octahedral in these glasses. The effects of magnetic exchange on the EPR features are discussed. [ABSTRACT FROM AUTHOR]

Magnetic glasses compositions: xFe2O3 + (30 - x)V2O5 + 30Na2O + 40B2O3 (x = 0, 2, 3, 5, 7, 10, and 15), abbreviated as FVNBx, are prepared with conventional melt-quenching technique, and the structural, physical, and electrical properties of compositions are investigated. The amorphous nature of the FVNBx glasses is confirmed using X-ray diffraction technique. It is found that the density of the glasses increases with x. The molar volumes calculations are based on the molar mass and the density data, which are then correlated with the structural changes. The decrease in the theoretical optical basicity shows marginal increase in the covalence of oxygen, when the V2O5 content is replaced with Fe2O3. The Fourier transform infrared spectroscopy that is carried out in the mid-IR region, shows the absence of the six-atomic (B3O3) boroxol rings. In this paper, the IR absorption bands corresponding to the combined contributions of tri and tetra borate vibrations are identified. The distinct IR spectra of the samples with different x indicates that the iron acts as a strong glass modifier, and brings only noticeable microstructural changes in the glass structures. Fe2O3 is believed to act as both glass former and glass modifier. The increase of DC electrical conductivity with temperature indicates a semiconducting nature of the glasses. The replacement of V2O5 by Fe2O3, even by 1 mol%, decreases the DC conductivity by an order of magnitude, and increases the activation energy by a factor of two. Composition, frequency, and temperature dependence of different dielectric parameters, namely dielectric constant, dielectric loss, loss tangent tan(δ), electrical modulus M*, etc., are also analyzed. [ABSTRACT FROM AUTHOR]

Glasses with compositions x(2NiO.V2O5).(30-x)Li2O.20Bi2O3.50B2O3, where x=0, 2, 5 and 7 (LBB, NVLBB1, NVLBB2 and NVLBB3, respectively), 7NiO.23Li2O.20Bi2O3.50B2O3 (NLBB) and 7NiO.23Li2O.20Bi2O3.50B2O3 (VLBB) are prepared by melt-quenching. The as-prepared samples have been analysed by differential scanning calorimetry (DSC) over the temperature range 200-900°C, infrared spectroscopy (FTIR) over the wave number range 400-1600 cm-1 and UV-Vis-NIR spectra over the wavelength range 300-2600 nm. The trends of these properties are attributed to changes in the glass network structure. Thermal studies using DSC curves reveal that the glass transition temperature (Tg) of all the glass samples increases with increasing transition metal oxide content in pure lithium bismuth borate glass (LBB). A single peak crystallization temperature (Tx) is observed when individual transition metal ions, i.e. Ni2+ or VO2+ is added to the base glass (LBB), whereas two crystallization temperatures are obtained when 2NiO.V2O5 as a whole is introduced into LBB glass. FTIR studies reveal that Ni2+ and VO2+ ions lead to structural rearrangements and bismuth exists in [BiO6] octahedral units only, whereas boroxol rings are absent in the glass network. Optical studies of NLBB and NVLBB glasses indicate that the Ni2+ ions occupy only octahedral positions in the glass network, whereas no optical transition was found in the VLBB system. Ligand field theory has been applied for analysis of the optical absorption results. The Racah parameter B (inter-electronic repulsion) and crystal field strength (Δoct) are calculated for these transitions in the absorption spectra. Nephelauxetic ratio (β), and optical band gap (Eg) are also evaluated. The infrared spectroscopic results are corroborated by the optical absorption analysis results. [ABSTRACT FROM AUTHOR]

Bismuth borate glasses with composition 20Bi2O3.80B2O3 containing 2·0 mol% of transition metal ions having magnetic character (Cu2+, Co2+, Ni2+, and Fe3+) prepared by the melt-quench technique have been investigated for their structural, thermal and optical properties. Glass formation is confirmed by x-ray diffraction (XRD). The density (D) and molar volume (Vm) of prepared have been measured and correlated with the structural changes. Differential thermal analysis (DTA) and thermogravimetric analysis (TGA) are carried out in the temperature range of 200-1000°C. The glass transition temperature (Tg) and glass melting temperature (Tm) are found to increase on adding transition metal ions (TMIs) to the bismuth borate glass matrix indicating the decreased glass fragility. The absence of weight loss observed from the TGA thermographs shows that the synthesized compositions are non-volatile. Study of infrared (IR) spectroscopy in mid-IR range (400-4000 cm-1) reveals an increase in tetrahedrally coordinated boron atoms and hence formation of nonbridging oxygens (NBOs). The optical band gap (Eopt), band tailing parameter (B) and Urbach energy (DE) are calculated and reported from the optical absorption results. A decrease in optical band gap is observed on adding transition metal ions to pure bismuth borate glass. [ABSTRACT FROM AUTHOR]