Magnetic properties of xCuO · (1 - x) [2B2O3 · PbO] glasses

The results of magnetic studies on xCuO · (1 ? x) [2B₂O₃ · PbO] glasses with 0 ? x ? 50 mol.%, are reported. These results evidenced that the copper ions, in this glass system, are in Cu²⁺ and Cu⁺ valence states. From Curie constant is determined the amount of the copper ions in bivalent state. For glasses with x > 5 mol.% CuO, an antiferromagnetic behaviour is evidenced.     

Ultrasonic and FT-IR studies on Bi2O3–Er2O3–PbO glasses

Glasses in the 90Bi₂O₃–(10?x)Er₂O₃?xPbO (x = 3, 5, 7, 9 and 10 mol%) system have been prepared by the melt-quenching technique. Elastic properties and FT-IR spectroscopic studies have been employed to study the role of PbO in the structure of the investigated system. Elastic properties and Debye temperature were recorded using sound wave velocity measurements at 4 MHz at room temperature. The results showed that density increased and molar volume decreased, while both sound velocities increased with an increase in x. Infrared spectra of the glasses revealed that the bismuthate network is affected by an increase in PbO content. The results are interpreted in terms of the conversion of [BiO₆] into [BiO₃] structural units, indicating that Pb ions have been substituted for erbium ions as tetrahedral network formers. The elastic moduli increased with increasing PbO content due to the increased average bond strength and degree of connectivity, as a direct effect of the increase in [BiO₃] structural units.     

Solid-state NMR study of bioactive binary borosilicate glasses

A series of binary borosilicate glasses prepared by the sol-gel method are shown to be bioactive. Tetraethyl orthosilicate (TEOS) and trimethylborate (TMB) in acidic medium are used to prepare xB₂O₃·(1−x)SiO₂ glass systems for x=0.045-0.167. The formation of a layer of apatite-like mineral on the glass surface becomes apparent after soaking in simulated body fluid for 48 h. We have measured the ¹¹B-¹¹B homonuclear second moments of the borosilicate glasses and inferred that no macroscopic phase separation occurred in our glasses. The ¹¹B chemical shift data also show that the formation of clustered boroxol rings is negligible in our glass system. Although the bioactivity of our borosilicate glasses is less than that of CaO-SiO₂ sol-gel glasses, these simple binary systems could be taken as reference glass systems for the search of new bioactive borosilicate glasses.     

Optical properties of vanadium-doped bismuth borate glasses before and after gamma-ray irradiation

UV–visible, infrared and Raman spectra, together with thermal properties, were measured for glasses from the system Bi₂O₃–B₂O₃–V₂O₅ before and after successive gamma irradiations. The UV–visible spectrum of the undoped glass before irradiation reveals five UV bands at 210, 275, 310, 350 nm, an intense band at 380 nm and a visible band at 420 nm due to the possible combined presence of trace iron impurities and Bi³⁺ ions. The V-doped glasses reveal six UV bands and two visible bands, probably arising from vanadium ions in three possible valencies, V³⁺, V⁴⁺ and V⁵⁺, beside that due to trace iron impurity beside Bi³⁺ ions. The spectra reveal an obvious resistance of the glasses to successive gamma irradiation. The Raman and infrared spectra show characteristic absorption bands, which indicate the sharing of Bi³⁺ ions as glass-forming (BiO₆) octahedral units together with the presence of various groups of the borate network.     

Effect of CuO addition on the optical and electrical properties of sodium zinc borophosphate glasses

Sodium borophosphate glasses doped with copper ions having general composition 20Na₂O-20ZnO-25B₂O₃-(35-x) P₂O₅-x CuO (x=1-8 mol %) were prepared using conventional melt-quench method and characterized by density, UV-visible optical absorption, photoluminescence and conductivity measurements. E_optical values for different glass samples are found to decrease systematically from 3.5 to 2.5 eV with increase in CuO content in the glass. Network modifying action of CuO with the glass network has been confirmed from the UV-visible optical absorption studies. Presence of Copper in the form of Cu⁺ species has been confirmed from photoluminescence measurements. The electrical conductivity (σ) increases with increase in copper oxide content in the glass and temperature dependence of electrical conductivity confirmed the semiconducting nature of the samples.     

Magnetic properties of xCoO.(1−x)[2B2O3.PbO] glasses

The results of magnetic studies on xCoO.(1?x)[2B₂O₃.PbO] glasses with 0?x?50 mol.%, are reported. These results show evidence that the cobalt ions, in this glass system, are in bivalent state and magnetically isolated, having magnetic moments μ=(4.50±0.06)μ_B.     

Bismuth silicate glass as host media for some selected rare-earth ions and effects of gamma irradiation

Ultraviolet, visible and infrared spectral measurements were used to investigate prepared undoped and rare-earth doped (2.5%) bismuth silicate glasses (80% Bi₂O₃–20%SiO₂) before and after being subjected to gamma irradiation (8?Mrad). The base bismuth silicate glass reveals strong extended UV–near visible absorption bands which are attributed to the presence of trace iron impurities in the raw materials together with absorption due to sharing of Bi³⁺ ions. The RE-doped samples show the same strong UV–near visible bands as the undoped glasses beside extra narrow characteristic bands mostly in the visible and near-infrared regions due to the respective studied rare-earth ions. The base undoped and all RE-doped samples except CeO₂ sample reveal quite resistance to the effect of gamma irradiation due to heavy atomic mass Bi³⁺ ions present in high content (80%) and the rare-earth ions are known to be weakly affected due to the known 5s, 5p shielding. The exceptional effect of CeO₂-doped sample is related to the ability of Ce³⁺ ions to change its oxidation state through photochemical reaction by irradiation or exchange with Fe³⁺ present as trace iron impurities. The FT infrared spectra of the prepared glasses reveal characteristic absorption bands which are related to the silicate groups together with the sharing of vibrational modes due to Bi–O groups. The IR spectra are slightly affected by gamma irradiation indicating the stability of the structural network groups consisting of SiO₄ and BiO₆ units.     

Effect of Bi2O3 content on physical and optical properties of 15Li2O-15K2O-xBi2O3-(65−x) B2O3: 5V2O5 glass system

Multi-component bismuth borate glasses doped with vanadium ions 15Li₂O-15K₂O-xBi₂O₃-(65−x) B₂O₃: 5V₂O_5, (x=3, 5, 7, 10, 12 and 15) have been prepared using conventional melt quench technique. Characterization of the prepared glasses has been done using X-ray diffraction, differential scanning calorimetry and density measurements. The effect of Bi₂O₃ content on the optical properties of the present glass system is studied from the optical absorption spectra recorded in the wavelength range 200-800 nm. The fundamental absorption edge has been identified from the optical absorption spectra. The values of optical band gap for indirect allowed transitions have been determined using available theories. The origin of the Urbach energy is associated with the phonon-assisted indirect transitions. The density and molar volume studies indicate that Bi₂O₃ in these glasses is acting partly as network modifier and partly as network former. The variations in the optical band gap energies, density and molar volume with Bi₂O₃ content have been discussed in terms of changes in the glass structure. Values of the theoretical optical basicity, average crosslink density and the average electronic polarizability are also reported.     

Spectroscopical splitting of Cu ion energy levels in magnesium lead fluoro silicate glasses

Homogeneous 40.0 MgO-(10-x) PbF₂-50.0 SiO₂: x CuO glasses were prepared using melt-quenching technique under controlled conditions. Spectroscopic studies (UV-vis absorption, ESR, FT-IR) are carried out for these glasses. One broad characteristic visible absorption band is observed around 700-850 nm in these glasses, the optical band gap decreases as the content of the CuO increases in the glass network up to 0.7 mol % then reversal trend is observed. ESR spectra of all these glasses show resonance peaks characteristic of Cu²⁺ ions and hyperfine splitting is resolved with increasing the CuO content in the glass network. From the observed ESR spectra, the spin-Hamiltonian parameters have been evaluated and indicate that Cu²⁺ ions have octahedral coordination with a strong tetragonal distortion in these glasses. By correlating ESR and optical absorption data, the molecular orbital coefficients have been evaluated. FT-IR spectra give important information about the nature of bonds in the glass matrix. The density of the glasses is also measured and is found to decrease with the increase CuO contents in the glass matrix. The physical parameters along with spectroscopic parameters are measured.     

Luminescence centers in silicate and germanate glasses activated by bismuth

Concentration series of silicate and germanate glasses activated by bismuth are studied. It is shown that luminescence in the IR region is controlled by several active centers related to bismuth. Based on a comparison of spectroscopic characteristics of the studied glasses with the data previously obtained for chloride glass, the observed centers were identified as Bi⁺, Bi ₂ ⁴⁺ , and Bi ₅ ³⁺ in germanate glass and Bi⁺, Bi ₂ ⁴⁺ in silicate glass.     

Glass Transition (T g) And Ftir Study Of Na2O-CuO-Bi2O3-P2O5 Glasses

(40?x)Na₂O-xCuO-10Bi₂O₃-50P₂O₅ glasses (0 h x h 40) were prepared and studied. Their density, molar volume, glass transition temperature and IR spectroscopy have been investigated in order to understand the structural role of Bi₂O₃ and CuO in these glasses. In the sodium bismo-phosphate glass, the structures consist of some phosphate chains linked together through P-O-Bi bonds. When copper oxide is added to sodium bismo-phosphate glass, phosphate chains are depolymerised by the incorporation of Cu through P-O-Cu bonds. The former bonds are the origin of the partial glass forming ability of Bi³⁺ and Cu²⁺.     

Investigation of structural,physical and optical properties of CeO2–Bi2O3–B2O3 glasses

xCeO₂–30Bi₂O₃–(70−x) B₂O₃ glasses are synthesized by using the melt quench technique. A number of studies such as XRD, density, molar volume, optical band gap, refractive index and FTIR spectroscopy are employed to characterize the glasses. The band gap decreases from 2.15 to 1.61 eV, refractive index increases from 2.67 to 2.93 and density increases from 4.151 to 4.633 g/cm³. The decrease in band gap with CeO₂ doping approaches the semiconductor behavior. FTIR spectroscopy reveals that incorporation of CeO₂ into glass network helps to convert the structural units of [BO₃] into [BO₄] and results in Bi–O bond vibration of [BiO₆].     

Effect of ZnO/CdO on the structure and electrical conductivity in Li2O·MO·Bi2O3·B2O3 glasses (M=Zn, Cd)

Studies of structural and electrical properties have been carried out on a number of glasses with wide ranging compositions in the glass systems Li₂O·MO·Bi₂O₃·B₂O₃ (where M=Zn or Cd), in order to understand the effect of transition metal (TM) ions on the structure of these glasses. The density and molar volume measurements have also been made to understand the structural changes occurring in these glasses. The dc conductivity measured in the temperature range 423-623 K obeys Arrhenius law. It increases with increase in Li₂O/MO ratio. The results of infrared spectra indicate that TM ions (Zn²⁺ or Cd²⁺) behave as network former in the present system. Boron exists in both tri- and tetra-hedral units in these glasses and no boroxol ring formation takes place in the glass structure. Values of theoretical optical basicity have also been reported.     

Thermal stability and spectroscopic properties of Er-doped lead fluorogermanate glasses

The thermal characterization and spectroscopic properties of Er³⁺-doped 0.6GeO₂-(0.4-x)PbO-xPbF₂ glasses were investigated experimentally. With the replacement of PbO by PbF₂ the thermal stability of glasses is improved and the infrared fluorescence intensity at 1530 nm is increased. The Judd-Ofelt intensity parameters, radiative transition rates, and fluorescence lifetimes of the excited ⁴I_13/2 level of Er³⁺ ions were calculated from Judd-Ofelt theory. The asymmetric ligand field around Er³⁺ ions resulted from the incorporation of PbF₂ into germanate glasses, broadens the infrared emission spectra at 1530 nm. Upconversion luminescence in the investigated glasses was observed at room temperature under the excitation of 976 nm laser diode. The glass 0.6GeO₂-0.3PbO-0.1PbF₂ exhibits the maximum upconversion emission intensity, while no frequency upconversion luminescence was observed in the 0.6GeO₂-0.4PbO glass. The quadratic dependence of the green and red emissions on excitation power indicates that two-photon absorption contributes to the visible emission under the 976-nm excitation.     

Comparative study of thermal stability and crystallization kinetics of 70B2O3-30Bi2O3 and 70B2O3-30PbO glasses

Glasses with compositions 70B₂O₃-30Bi₂O₃ and 70B₂O₃-30PbO have been prepared and studied by differential thermal analysis (DTA). The crystallization kinetics of the glasses were investigated under non-isothermal conditions. From the dependence of glass-transition temperature (T_g) on heating rate, the activation energy for the glass transition was derived. Similarly the activation energy of the crystallization process was determined. Thermal stability of these glasses were achieved in terms of the characteristic temperatures, such as glass-transition temperature, T_g, onset temperature of crystallization, T_in, temperature corresponding to the maximum crystallization rate, T_p, beside the kinetic parameters, K(T_g) and K(T_p). The results revealed that 70B₂O₃-30PbO is more stable than 70B₂O₃-30Bi₂O₃. The crystallization mechanism is characterized for both 70B₂O₃-30Bi₂O₃ and 70B₂O₃-30PbO glasses (kinetic exponent n=2.06 for 70B₂O₃-30Bi₂O₃, and n=3.03 for 70B₂O₃-30PbO). The phases at which the glass crystallizes after the thermal process were identified by X-ray diffraction.     

Magnetic properties of xNiO. (1-x)[2B2O3.PbO] glasses

The results of magnetic studies on xNiO.(1-x)[2B₂O₃.PbO] glasses with 0 ? x ? 40 mol.% are reported. These results evidenced that the nickel ions, in this glass system, are in a divalent state and magnetically isolated. The magnetic moments, μ, decrease from a value 3.31 μ_B for the 5 mol.% NiO to a value 2.90 μ_B for 40 mol.% NiO. These variations can be due to the result of a statistical average of the nickel sites distribution.     

Effect of Bi2O3 on EPR, optical transmission and DC conductivity of vanadyl doped alkali bismuth borate glasses

Glasses with composition xBi₂O₃·(30−x)M₂O·70B₂O₃ (M=Li, Na) containing 2 mol% V₂O₅ have been prepared over the range 0≤x≤15 (x is in mol%). The electron paramagnetic resonance spectra of VO²⁺ of these glasses have been recorded in the X-band (≈9.3 GHz) at room temperature (RT≈300 K). Spin Hamiltonian parameters, g_∥, g_⊥, A_∥, A_⊥, dipolar hyperfine coupling parameter, P, and Fermi contact interaction parameter, K, have been calculated. The molecular orbital coefficients, α² and γ², have been calculated by recording the optical transmission spectra. In xBi₂O₃·(30−x)Li₂O·70B₂O₃ glasses there is decrease in the tetragonality of the V⁴⁺O₆ complex for x up to 6 mol% whereas for x≥6 mol%, tetragonality increases. In xBi₂O₃·(30−x)Na₂O·70B₂O₃ glasses there is increase in the tetragonality of the V⁴⁺O₆ complex with increasing x. The 3d_xy orbit expands with increase in Bi₂O₃:M₂O ratio. Values of the theoretical optical basicity, Λ_th, have also been reported. The DC conductivity increases with increase in temperature. The order of conductivity is 10⁻⁵ ohm⁻¹ m⁻¹ at low temperature and 10⁻³ ohm⁻¹ m⁻¹ at high temperature. The DC conductivity decreases and the activation energy increases with increase in Bi₂O₃:M₂O ratio.     

Structural investigation of xAg2O·(100−x)·[2B2O3·As2O3] glasses doped with manganese ions

Structural analysis of x[(100−y)Ag₂O·yMnO]·(100−x)[2B₂O₃·As₂O₃] glasses, with x=10 mol% and 0≤y≤10 mol%, was performed by means of FT-IR and FT-Raman spectroscopies. The purpose of this work is to investigate the structural changes that appear in the xAg₂O·(100−x)·[2B₂O₃·As₂O₃] glasses with the addition and increase in manganese ions content. FT-IR measurements revealed the presence of pyro-, ortho-, di-, tri-, tetra- and penta-borate groups and structural units characteristic to As₂O₃ in the structure of the studied glasses. FT-IR spectroscopy measurements also show that BO₃ units are the main structural units of the glass system. The presence of structural units characteristic to Ag₂O were not directly evidenced by FT-IR spectroscopy. In addtition, the FT-Raman analysis evidenced the presence of boroxol rings in the structure of the studied glasses.     

On the iron valence states in B2O3-PbO-GeO2 glasses

The Mössbauer effect measurements performed on 20Fe₂O₃ 80 3B₂O₃ (1?x)PbO xGeO₂ glasses show that the ratio between the number of ferrous ions to the total number of iron ions decreases by increasing the GeO₂ content. The Curie constants calculated from the distribution of iron cations obtained by Mössbauer effect data are in agreement with the values determined from magnetic measurements. Finally, we discuss the influence of the glass composition and melting temperature on the iron valence states.