Modification in structural and optical properties of ZnO, CeO2 doped Al2O3-PbO-B2O3 glasses

The structural and optical analysis of glasses is carried out by XRD, FTIR, density and UV visible spectroscopic measurement techniques. XRD results have confirmed the glassy nature of the samples. The FTIR spectral analysis reveals that with the combined presence of ZnO and CeO₂ contents in Al₂O₃-PbO-B₂O₃ glasses, more BO₃ groups are transformed into BO₄. The optical analysis reveals that optical band gap energy decreases more for CeO₂-ZnO-Al₂O₃-PbO-B₂O₃ glasses (from 2.28 to 1.84 eV). The presence of CeO₂ and ZnO in the glass samples causes more compaction of the borate network due to the formation of more BO₄ groups and the presence of ZnO₄ groups, which results an increase in density, refractive index and decrease of molar volume.     

Conversion of covalent to ionic character of V2O5–CeO2–PbO–B2O3 glasses for solid state ionic devices

xV₂O₅–xCeO₂–(30−x)PbO–(70−x) B₂O₃ glasses are synthesized by using the melt quench technique. The 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 2.20 to 1.78 eV and density increases from 3.49 to 4.25 g/cm³. FTIR spectroscopy reveals that incorporation of V₂O₅ in glass network helps to convert the structural units of [BO₃] into [BO₄]. At higher concentration of vanadium, VO vibration of [VO₅] structural units and V–O–V vibration are present. The bond ionicity of glasses increases with incorporation of V₂O₅ contents.     

Role of WO3 in structural and optical properties of WO3-Al2O3-PbO-B2O3 glasses

Glass samples of composition xAl₂O₃-20PbO-(80−x)B₂O₃ and xWO₃-xAl₂O₃-20PbO-(80−2x)B₂O₃ with x varying from 0% to 10% mole fraction are prepared by melt quench technique. The optical band gap decreases (from 3.21 to 2.37 eV) more for WO₃-Al₂O₃-PbO-B₂O₃ glasses with an addition of WO₃ content. The FTIR spectral studies have pointed out the conversion of structural units of BO₃ to BO₄ and WO₄ to WO₆ in these glasses. The increase in density from 4.51 to 5.80 g cm⁻³ for WO₃-Al₂O₃-PbO-B₂O₃ glasses is observed with an increase in WO₃ content. This is observed that the atomic structure changes more with the incorporation of WO₃. This is due to the formation of WO₆, WO₄ and BO₄ units.     

Nonlinear optical properties of 75TeO2－20Nb2O5－5ZnO glasses doped with CeO2

Nonlinear optical properties of 75TeO_2－20Nb_2O_5－5ZnO glasses doped with CeO_2 have been investigated with a self-diffracted time-resolved degenerate four-wave mixing (DFWM) technique at different excitation intensities and lattice temperatures. The DFWM signal exhibits three peaks at higher excitation intensities, where a main peak appears at zero delay time and two rather weak side peaks are located symmetrically at the negative and positive time delay. Due to destructive interferences between the fifth- and third-order polarizations, the line-shape of the main peak around the zero time delay evolves from single peak into a double-peak structure with increasing excitation intensity. Two side peaks emerge at the positive and negative time delay and gradually intensify with increasing excitation intensity or lattice temperature, and their positions are independent of the pulse duration, temperature and excitation intensity, which are attributed to the many-body Coulomb interaction.     

Effect of WO3 on structural and optical properties of CeO2-PbO-B2O3 glasses

Pure and WO₃ doped CeO₂-PbO-B₂O₃ glasses are prepared by the melt-quench technique. The structural and optical analyses of glasses are carried out by XRD, FTIR, density and UV-vis spectroscopic measurement techniques. FTIR analysis indicates the transformation of structural units of BO₃ into BO₄ with W-O-W vibration and the presence of WO₄ and WO₆ units observed with increase in WO₃ contents. Decrease in band gap for CeO₂-PbO-B₂O₃ glasses from 2.89 to 2.30 eV and for WO₃ doped glasses from 2.89 to 1.95 eV has been observed and discussed. This decrease in band gap with WO₃ doping approaches to semiconductor behavior. It shows that the presence of WO₃ in the glass samples causes more compaction of the borate network due to the formation of BO₄ groups and the presence of WO₄ and WO₆ groups, which result in a decrease in the optical band gap energy and increase in the density.     

Spectroscopic studies on Fe and Mn doped SrB4O7 glasses

EPR and optical absorption studies on Fe³⁺ and Mn²⁺ doped strontium tetraborate (SrB₄O₇) glasses are carried out at room temperature. The EPR spectrum of the Fe³⁺ doped glass consists of signals with g-values 9.04, 4.22 and 2.04, whereas the EPR spectrum of Mn²⁺ doped glass exhibits a characteristic hyperfine sextet around g=2.0. The spectroscopic analyses of the obtained results confirmed distorted octahedral site symmetry for the Fe³⁺ and Mn²⁺ impurity ions. Crystal field and Racah parameters evaluated from optical absorption spectra are: Dq=790, B=700 and C=3000 cm⁻¹ for Fe³⁺doped glass and Dq=880, B=700 and C=2975 cm⁻¹ for Mn²⁺ doped glass.     

The structural properties of CdO-Bi2O3 borophosphate glass system containing Fe2O3 and its role in attenuating neutrons and gamma rays

A glass system with chemical formula xBi₂O₃-(30−x)CdO-10B₂O₃-20Fe₂O₃-40P₂O₅ (0≤x≤30) wt% is prepared to be used as radiation shield. The mass attenuation coefficient and half value layer of the glass system to gamma rays have been measured experimentally and compared with those determined from theoretical calculations using the mixture rule of WinXCom program. A database of effective mass removal cross-sections for fast neutrons is also introduced in this work. The obtained results of this study are correlated to the structural properties of these glasses obtained from their IR spectra and the influence of gamma and neutrons irradiation on these structural properties.     

Effect of WO3 on EPR, structure and electrical conductivity of vanadyl doped WO3·M2O·B2O3 (M=Li, Na) glasses

Glasses with composition xWO₃·(30−x)M₂O·70B₂O₃ (M=Li, Na; 0≤x≤15) doped with 2 mol% V₂O₅ have been prepared using the melt-quench technique. The electron paramagnetic resonance spectra have been recorded in X-band (ν≈9.14 GHz) at room temperature (RT). The spin Hamiltonian parameters, dipolar hyperfine coupling parameter and Fermi contact interaction parameter have been calculated. It is observed that the resultant resonance spectra contain hyperfine structures (hfs) only due to V⁴⁺ ions, which exist as VO²⁺ ions in octahedral coordination with a tetragonal compression in the present glass system. The tetragonality increases with WO₃:M₂O ratio and also there is an expansion of 3d_xy orbit of unpaired electron in the vanadium ion. The study of IR transmission spectra over a range 400-4000 cm⁻¹ depicts the presence of WO₆ group. The DC conductivity (σ) has been measured in the temperature range 423-623 K and is found to be predominantly ionic.     

Optical properties of (ZnO)0.5(P2O5)0.5 glasses doped with Gd2O3:Eu nanoparticles and Eu2O3

Binary (ZnO)_0.5(P₂O₅)_0.5 glasses doped with Eu₂O₃ and nanoparticles of Gd₂O₃:Eu were prepared by conventional melt-quench method and their luminescence properties were compared. Undoped (ZnO)_0.5(P₂O₅)_0.5 glass is characterized by a luminescent defect centre (similar to L-centre present in Na₂O-SiO₂ glasses) with emission around 324 nm and having an excited state lifetime of 18 ns. Such defect centres can transfer the energy to Eu³⁺ ions leading to improved Eu³⁺ luminescence from such glasses. Based on the decay curves corresponding to the ⁵D₀ level of Eu³⁺ ions in both Gd₂O₃:Eu nanoparticles incorporated as well as Eu₂O₃ incorporated glasses, a significant clustering of Eu³⁺ ions taking place with the latter sample is confirmed. From the lifetime studies of the excited state of L-centre emission from (ZnO)_0.5(P₂O₅)_0.5 glass doped with Gd₂O₃:Eu nanoparticles, it is established that there exists weak energy transfer from L-centres to Eu³⁺ ions. Poor energy transfer from the defect centres to Eu³⁺ ions in Gd₂O₃:Eu nanoparticles doped (ZnO)_0.5(P₂O₅)_0.5 glass has been attributed to effective shielding of Eu³⁺ ions from the luminescence centre by Gd-O-P type of linkages, leading to an increased distance between luminescent centre and Eu³⁺ ions.     

Crystallization kinetics of Li2O-PbO-V2O5 glasses

Lead vanadate glasses of the system 5Li₂O−(45−x) PbO−(50+x) V₂O₅, with x=0, 5, 10, and 15 mol% have been prepared and studied by differential scanning calorimetry (DSC). The crystallization kinetics of the glasses were investigated under non-isothermal conditions applying the formal theory of transformations for heterogeneous nucleation to the experimental data obtained by DSC using continuous-heating techniques. In addition, from dependence of the glass-transition temperature (T_g) on the heating rate, the activation energy for the glass transition was derived. Similarly the activation energy of the crystallization process was determined and the crystallization mechanism was characterized. The results reveal the increase of the activation energy for glass transition which was attributed to the increase in the rigidity, the cross-link density and the packing density of these glasses. The phases into which the glass crystallizes have been identified by X-ray diffraction. Diffractograms of the transformed material indicate the presence of microcrystallites of Li_0.30V₂O₅, Li_0.67O₅V₂, LiV₆O₁₅, Li₄O₄Pb, and O₇Pb₂V₂ in a remaining amorphous matrix.     

Structural and optical properties of WO3-ZnO-PbO-B2O3 glasses

Glass samples of compositions 20PbO-80B₂O₃ and xWO₃—(20−x) ZnO-20PbO-60B₂O₃ with x varying from 0% to 10% mole fraction are prepared by the melt quench technique. Decrease in the band gap from 2.86 to 2.16 eV for ZnO-PbO-B₂O₃ glasses with an increase in the WO₃ content has been observed and discussed. The FTIR spectral studies have pointed out the conversion of structural units of BO₃ to BO₄ and WO₄ to WO₆ with the presence of W-O-W vibration of tungsten and incorporation of ZnO₄ structural units of zinc in these glasses. The increase in density from 2.75 to 4.03 gcm⁻³ for ZnO-PbO-B₂O₃ glasses is observed with an increase in WO₃ content. Due to the formation of WO₆, WO₄ and BO₄ units, changes in the atomic structure with WO₃ composition are observed and discussed.     

Optical properties of Er in MoO3-Bi2O3-TeO2 glasses

Erbium-doped MoO₃−Bi₂O₃−TeO₂ (MBT) glasses suitable for broadband optical amplifier applications have been fabricated and characterized optically. The maximum phonon band of undoped glasses is at 915 cm⁻¹, and the emission from the Er³⁺: ⁴I_13/2 → ⁴I_15/2 transition locates around 1.53 μm with a full width at half maximum (FWHM) of ∼80 nm. The lifetime and quantum efficiency of the ⁴I_13/2 level are 2.13 ms and ∼90%, respectively. Under the same measurement condition, the upconversion emission intensities at 550 nm in Er³⁺-doped MBT glasses is about 30 times weaker than that in Er³⁺-doped Na₂O−ZnO−TeO₂ (NZT) glasses.     

Long lasting phosphorescence of Eu in reduced SrO-B2O3 glasses

The blue long-lasting phosphorescence (LLP) phenomenon was observed for Eu²⁺-doped SrO-B₂O₃ glasses prepared in the reducing atmosphere. The phosphorescence peaks at about 450 nm due to the 4f5d→4f transition of Eu²⁺. With the doping of different amounts of Eu²⁺, the concentration-quenching phenomenon was observed for both the LLP and photoluminescence of the glasses, and the critical concentration for the two cases was same, i.e., 0.02 mol% Eu²⁺. And by the investigation of the TL curves, the content of Eu²⁺ had an effect on the trap depth of the samples. At last the possible mechanism of the LLP of the samples was suggested.     

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.     

Spectroscopic studies on Pb3O4-ZnO-P2O5 glasses doped with transition metal ions

Optical absorption, Electron Paramagnetic Resonance (EPR) studies are carried out on lead zinc phosphate glass systems doped with Cr³⁺ and VO²⁺. From optical absorption investigations the crystal-field parameters Dq, B and C are evaluated. EPR measurements on Cr³⁺ systems indicate that Cr³⁺ ions are located at sites with low symmetry. EPR spectra of vanadyl doped system revealed the characteristic nature of vanadyl ion. Spin-Hamiltonian and hyperfine values are evaluated for both the systems. Optical absorption spectra of vanadyl doped system revealed three bands that are characteristic of VO(II) ion in tetragonally distorted octahedral site. By correlating both EPR and optical data, the dipolar coupling constant (P) and Fermi-constant coupling parameter (κ) and molecular orbital coefficients β^?2, e_π^?2 are evaluated. Electron Paramagnetic Resonance and optical absorption studies showed that the chemical bonds of Cr³⁺ ions and VO²⁺ ions with the ligands have more covalent nature. From these studies it is also observed that lead spinals are playing major key role in sustaining the covalent nature of bonding.     

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.     

Optical absorption and thermoluminescence studies on LiF-Sb2O3-B2O3 glasses doped with Ni ions

20LiF-(30−x)Sb₂O₃-50B₂O₃:xNiO glasses with the value of x (ranging from 0 to 1.0 mol% in steps of 0.2) were prepared. A number of studies, viz. differential scanning calorimetry, optical absorption, magnetic susceptibility and thermoluminescence, on these glasses were carried out as a function of nickel ion concentration. An anomaly has been observed in all the properties of these glasses when NiO concentration is about 0.6 mol%. The results of these studies were analysed in the light of different environments of nickel ions in the glass network.     

Ga2O3组分对Tm3+掺杂GeO2-Ga2O3-Li2O-BaO-La2O3玻璃的光谱性能影响

制备了Tm³⁺(8.0mol%)掺杂(77-x)GeO₂-xGa₂O₃-8Li₂O-10BaO-5La₂O₃(x=4,8,12,16)系列玻璃.系统地研究了Ga₂O₃从4mol%变化到16mol%时,玻璃的光谱性质与热学性质的变化规律.差热分析表明,随着Ga₂O₃含量的增加,锗酸盐玻璃的热稳定性增加.运用Judd-Ofelt(J_O)理论计算得到了Tm³⁺在不同Ga₂O₃含量的GeO₂-Ga₂O₃-Li₂O-BaO-La₂O₃玻璃中的J-O强度参数(Ω₂,Ω₄,Ω₆)及Tm³⁺各激发能级的自发跃迁概率、荧光分支比以及辐射寿命等光谱参量.在808nm激光二极管的激发下,测试并分析了Ga₂O₃对Tm³⁺荧光光谱特性的影响.随着Ga₂O₃从4mol%增加到16mol%,Tm³⁺在1.8μm处的荧光强度呈现先减弱后增强的特性.当Ga₂O₃含量大约在12mol%时,Tm³⁺在1.8μm处的荧光强度最弱,受激发射截面达到最小.还初步讨论了Ga₂O₃对玻璃结构与光谱参数的影响规律. 关键词： 3+掺杂锗酸盐玻璃')" href="#">Tm³⁺掺杂锗酸盐玻璃 光谱性能 Judd-Ofelt参数 热稳定性     

The structure of AgI-Ag2O-V2O5 glasses

Structures of 10AgI-3Ag₂O-2V₂O₅, 3AgI-3Ag₂O---2V₂O₅ and 2AgI---2Ag₂O-V₂O₅ glasses have been investigated by neutron diffraction experiments. The characteristic features of observed structure factors S(Q) in 10AgI-3Ag₂O-2V₂O₅ glass is similar to those of other superionic conducting glasses and molten AgI. From the standpoint of the pair distribution functions, it is clarified that the Ag-I and I-I correlation strength and Ag---Ag correlation length increase with increasing AgI concentration. Observed results suggest that the local AgI structure accompanied by the re-arrangement of silver ions is formed with highly doped iodide ions.     

Study on vacancy motion in Y2O3-doped CeO2 by 17O NMR technique

The ¹⁷O NMR measurement was made to elucidate the microscopic nature of vacancy motion in Y₂O₃-doped CeO₂. Spin-lattice relaxation rate, T^?1₁, spin-spin relaxation rate, T^?1₂, and resonance intensity were measured at v₀ = 8.13 MHz as a function of temperature [385 < T (K) < 1110] and composition [$\text{0.06 <}\text{Y}{}_2\text{O}{}_3\text{(}\text{m}\text{o}\text{) < 6}$]. The static electric field gradient associated with lattice defects resulted in the composition dependences of the line width and the intensity. In low dopant concentrations, doubly peaked temperature dependence of T^?1₁ was found, while a single and asymmetric peak was observed in high concentrations. T^?1₁ of 4.0 and 6.0 $\text{m}\text{o}$ doped samples were analyzed using a barrier height distribution model for the oxygen vacancy jump. The mean value of the activation energy was found to increase with the Y₂O₃ concentration.