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Dahiya S.,Maharshi Dayanand University | Punia R.,Guru Jambheshwar University of Science and Technology | Punia R.,Indira Gandhi University | Murugavel S.,University of Delhi | Maan A.S.,Maharshi Dayanand University
Solid State Sciences | Year: 2016

The conductivity and modulus formulation in lithium modified bismuth zinc borate glasses with compositions xLi2O-(50-x) Bi2O3-10ZnO-40B2O3 has been studied in the frequency range 0.1 Hz-1.5 × 105 Hz in the temperature range 573 K-693 K. The temperature and frequency dependent conductivity is found to obey Jonscher's universal power law for all the studied compositions, the dc conductivity (σdc), crossover frequency (ωH), and frequency exponent (s) have been estimated from the fitting of the experimental data of ac conductivity with Jonscher's universal power law. Enthalpy to dissociate the cation from its original site next to a charge compensating centre (Hf) and enthalpy of migration (Hm) have been estimated. It has been observed that number of charge carriers and ac conductivity in the lithium modified bismuth zinc borate glasses increases with increase in Li2O content. Further, the conduction mechanism in the glass sample with x Combining double low line 0 may be due to overlapping large polaron tunneling, whereas, conduction mechanism in other studied glass samples more or less follows diffusion controlled relaxation model. The ac conductivity is scaled using σdc and ωH as the scaling parameter and is found that these are suitable scaling parameter for conductivity scaling. Non-Debye type relaxation is found prevalent in the studied glass system. Scaling of ac conductivity as well as electric modulus confirms the presence of different type of conduction mechanism in the glass samples with x Combining double low line 0 and 5 from other studied samples. The activation energy of relaxation (ER) and dc conductivity (Edc) are almost equal, suggesting that polarons/ions have to overcome same barrier while relaxing and conducting. © 2016 Elsevier Masson SAS. All rights reserved.


Parmar R.,Maharshi Dayanand University | Hooda J.,Guru Jambheshwar University of Science and Technology | Kundu R.S.,Guru Jambheshwar University of Science and Technology | Punia R.,Guru Jambheshwar University of Science and Technology | And 2 more authors.
International Journal of Optics | Year: 2015

The optical characterization of glass samples in the system 40SiO2 · x ZnO · (60 - x)Bi2O3 with x = 0, 5, 10, 15, 20, 25, 30, 35, and 40 prepared by conventional melt-quench technique has been carried out in the light of Hydrogenic Excitonic Model (HEM). The absorption coefficient spectra show good agreement with theoretical HEM for the present glass system and the values of different parameters like E g, R, Γ 1, Γ c, and C o have been estimated from fitting of this model. The values of energy band gap estimated from fitting of HEM with experimental data are in good agreement with those obtained from Tauc's plot for direct transitions. The band gap energy is found to increase with increase of ZnO content. The decrease in values of Urbach energy with increase in ZnO content indicates a decrease in defect concentration in the glass matrix on addition of ZnO content. Optical constants n and k obey k - k consistency and the dielectric response of the studied glass system is similar to that obtained for Classical Electron Theory of Dielectric Materials. The calculated values of the metallization criterion (M) show that the synthesized glasses may be good candidates for new nonlinear optical materials. © 2015 Rajesh Parmar et al.


Nanda K.,Guru Jambheshwar University of Science and Technology | Kundu R.S.,Guru Jambheshwar University of Science and Technology | Pal I.,Guru Jambheshwar University of Science and Technology | Punia R.,Guru Jambheshwar University of Science and Technology | And 2 more authors.
Journal of Alloys and Compounds | Year: 2016

Glass samples with compositions xSm2O3- (100-x)[0.1BaO-0.4ZnO-0.5B2O3]; x = 0.5, 1.0, 1.5 and 2.0 have been prepared using melt quench technique. Optical absorption and fluorescence spectra have been recorded for prepared glass samples at room temperature. The spectral intensities of Sm3+ transition observed in absorption spectra have been calculated by using Judd-Ofelt theory. The intensity parameters (Ω2, Ω4 and Ω6) have been estimated by applying least square fit method on the experimental (fexp) and calculated (fcal) oscillator strengths. The variation of Ω2 observed with the increase in Sm3+ ion concentration, is attributed to decease in covalency of rare earth oxygen bond due to change in optical basicity of host glass matrix. From the fluorescence spectra, four emission spectral lines have been observed that correspond to the transition from 4G5/2 ground state to lower lying 6H5/2, 6H7/2, 6H9/2 and 6H11/2 states with an excitation wavelength of 402 nm. The intensity parameters and the emission measurements have been used to estimate the various radiative parameters such as transition probabilities (AR), radiative lifetime (τR), branching ratio (βR) and stimulated emission cross-sections (σe) of luminescent levels. The value of σe is found to decrease with increase in concentration of Sm3+ ions and it possesses higher value for glass sample with x = 0.5 for transition lying in the visible region indicating its importance for photonic applications. © 2016 Elsevier B.V. All rights reserved.


Berwal N.,Guru Jambheshwar University of Science and Technology | Kundu R.S.,Guru Jambheshwar University of Science and Technology | Nanda K.,Guru Jambheshwar University of Science and Technology | Punia R.,Guru Jambheshwar University of Science and Technology | And 2 more authors.
Journal of Molecular Structure | Year: 2015

Quaternary bismuthate glasses with compositions xB2O3-(80 - x) Bi2O3-15SiO2-5TeO2 have been prepared by melt-quench technique. X-ray diffraction studies were performed to ascertain the amorphous nature of samples. The density, molar volume and crystalline volume decrease with increase in B2O3 content whereas the glass transition temperature shows the reverse trend. The Raman and FTIR spectra of the studied glasses indicate that B2O3 has been found to exist in the form of BO3 trigonal and BO4 tetrahedral structural units and vibrations corresponding to these structural units increase with increase in B2O3 content. SiO2 is present in the form of SiO4 tetrahedral structural units and TeO2 in the form of TeO3 structural units. Bismuth plays the role of network modifier [BiO6 octahedra] as well as network former [BiO3 pyramids] for all the glass compositions. The optical band gap energy has been calculated from the fitting of both Mott and Davis's model and Hydrogenic excitonic model with the experimentally observed absorption spectra. A good fitting of experimental data with HEM indicates the excitonic formation in the studies glass system. The values of optical band gap energy show nonlinear behavior due to the structural changes that take place in the present glass samples. The Urbach energy calculated using Urbach empirical formula for studied glass samples suggest the possibility of reduction in defect concentrations. The metallization criterion of the presently studied samples suggests that the prepared glasses may be potential candidates for nonlinear optical applications. © 2015 Elsevier B.V. All rights reserved.


Nanda K.,Guru Jambheshwar University of Science and Technology | Kundu R.S.,Guru Jambheshwar University of Science and Technology | Sharma S.,Guru Jambheshwar University of Science and Technology | Mohan D.,Guru Jambheshwar University of Science and Technology | And 3 more authors.
Solid State Sciences | Year: 2015

Samarium oxide doped Barium-Zinc-Borate glasses with compositions xSm2O3-(100-x)[0.1BaO-0.4ZnO-0.5B2O3]; x Combining double low line 0.0, 0.5, 1.0, 1.5 and 2.0 have been prepared by melt quench technique. The amorphous nature of as-prepared glasses has been ascertained by X-ray diffraction patterns. The observed values of density and molar volume of the glass samples are found to increase with the increase in concentration of Sm2O3. Fourier Transform Infrared spectra of the prepared glasses indicate that Sm2O3 acts as glass modifier. With the increase in Sm2O3 content, BO4 structural units start converting into BO3 structural units. The values of optical energy band gap (Eg), estimated from Tauc's plots, are observed to decrease with the increase in Sm2O3 content. The nonlinear optical properties of glass samples have been investigated by Z-scan method with nanosecond pulsed laser at gʇ1/4532 nm in both open and close aperture geometries. The values of two photon absorption coefficient (β) and nonlinear refractive index (n2) have been estimated by fitting of experimentally observed data with theoretical models and both are found to increase with the increase in Sm3+ ions concentration in the glass matrix. The total third order nonlinear susceptibility (χ(3)) have been calculated and observed to increase with the increase in Sm3+ ions concentration. © 2015 Elsevier Masson SAS. All rights reserved.

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