Li2SO4–MgO–P2O5 glasses mixed with a varied quantity of NiO were prepared. Detailed spectroscopic investigations (viz., OA, IR and Raman) spectra were carried out. Optical absorption spectral results ...indicated that Ni2+ ions in the glass network reside in octahedral (Oh) as well as tetrahedral (Td) sites; these results have also pointed out the growing concentration of Ni2+ ions in Oh sites as NiO concentration is increased up to 0.8 mol%. Results of infrared and Raman spectral studies indicated increased internal chaos in the sulpho-phosphate glass network with an increase of NiO concentration up to 0.8 mol%. Values of dielectric permittivity (both real and imaginary components), a.c. conductivity, σac, are observed to be gradually increasing with NiO content in the concentration range 0–0.8 mol%. Electric moduli spectra have exhibited dipolar relaxation effects and the dipolar relaxation time τ estimated from these spectra exhibited a decreasing trend with the raise of NiO quantity up to 0.8 mol%. The complexes of octahedral Ni2+ ions with oxygen ions are predicted to be the possible dipoles responsible for the dipolar effects. Variation of σac with NiO content exhibited an increasing trend up to 0.8 mol%. Quantitative analysis of this observation indicated ionic contribution to σac is dominant in the glasses containing small quantities of NiO (< 0.8 mol%), whereas in the glasses containing higher quantities of NiO (> 0.8 mol%) polaronic contribution to the conductivity seems to be present. Overall, the results of dielectric properties of studied glass system indicted that the glass with low quantities of NiO (< 0.8 mol%) can be considered as useful material as electrolytes in the solid-state batteries.
An illustration of entrenchment of SO42− structural unit in the disrupted phosphate glass network consisting of PO43− (Q0) units. Display omitted
•Spectral studies of Li2SO4–MgO–P2O5:NiO glasses indicated Ni2+ ions act as modifiers.•ε and σac found to increase with NiO content due to increased internal chaos in glass.•Dielectric studies indicated glasses with NiO (<0.8 mol%) are useful as electrolytes.
In vitro bioactivity studies (in SBF) and antibacterial activity studies (against S. aureus and E. coli bacteria) of SeO2 doped CaF2–CaO–B2O3–P2O5–SrO glasses were performed as a function of SeO2 ...content. X-ray diffraction and scanning electron microscopic studies indicated the formation of Se-HAp crystalline layer on the samples after immersing in SBF. Infrared and Raman spectral studies further established the deposition of hydroxyapatite layer on the surface of these samples. The thickness of HAp layer deposited on the samples is found to be dependent on the content of SeO2 dopant; this is assessed by measuring weight loss of the glasses due to dissolution in SBF and by measuring the variation of pH and the chemical analysis of the left-over fluid as functions of SeO2 content. The studies indicated the maximal content of hydroxyapatite is deposited on the surface the glasses doped with 4.0 mol% of SeO2. The studies on antibacterial effect against E. coli and S. aureus of the glasses indicated the maximal inhibition of bacteria in the samples doped with 4.0 mol%. This is ascribed to the presence of maximal concentration of SeO32- ions (confirmed by IR and Raman studies) in this glass sample. Overall, the results of bioactivity of SeO2 doped bioglasses indicated that the presence of SeO2 not only enhanced bioactivity potential but also facilitated increase of antimicrobial activity.
Antibacterial effect of SeO2 doped CaF2–CaO–B2O3–P2O5–SrO glasses against E. coli and S. aureus observed after 24 h. Display omitted
•In vitro bioactivity studies of SeO2 doped bioactive glasses are performed.•Antibacterial activity against S. aureus &E. coli bacteria of SeO2-BGs is assessed.•XRD and SEM studies proved formation of Se-HAp crystalline layer on the glasses.•Studies indicated maximal HAp deposition on BG doped with 4.0 mol% of SeO2.•Maximal bacterial killing effect is observed in the BG doped with 4.0 mol% of SeO2.
•Impact of HgO on dielectric properties and σac of Li2O-P2O5 glasses was explored.•ε′, σac exhibited increase with HgO upto 5 mol% w.r.t. pure sample.•Up to 5 mol% HgO ionic contribution to σac is ...predominant.•Beyond 5 mol% HgO polaronic tunneling became more significant.•Lithium phosphate glasses with 5 mol% HgO are suitable as solid electrolytes.
This study investigates the impact of HgO concentration on the dielectric properties and a.c. conductivity of the Li2O-P2O5 glass system. XRD, SEM, DSC and FT-IR spectral techniques were employed to analyze the structural variations of the samples due to the varying contents of HgO. The dielectric properties and σac were studied across wide temperature (T) and frequency (ω) ranges to understand the conduction phenomenon. The results revealed that the presence of 5 mol% HgO led to an increase in dielectric parameters and a.c. conductivity compared to those of pure sample. Variation of σac with HgO content indicated that up to 5 mol% HgO, the ionic contribution to σac was predominant, while beyond that, polaronic tunneling became more significant. Therefore, lithium phosphate glasses with 5 mol% HgO are suitable as solid electrolytes, while glasses doped with higher HgO concentrations are better suited as electrodes in ionic batteries.
By measuring ultrasonic velocity in Li
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glasses doped with different concentrations of NiO, we have evaluated different elastic coefficients; the values of these coefficients ...exhibited a decreasing trend with increase of nickel oxide concentration up to 0.8 mol%. This is ascribed to increasing presence of nickel ions in octahedral positions that act as modifiers and are predicted to have induced structural defects like dangling bonds in the glass network. Such increased degree of disorder in the glass network is anticipated to be a hindrance for the propagation of ultrasonic waves and hence caused the decrease in the velocities of ultrasonic waves and elastic coefficients. Overall, there is a decrease in mechanical strength of these glasses with increased content of nickel oxide up to 0.8 mol%.
Herein, a study on the dielectric properties of ZnO–P2O5–SeO2 glass ceramics containing varied contents of Ag2O is presented. Structural analysis of the samples by X‐ray diffraction, transmission ...electron microscopy, differential scanning calorimetry, Fourier transform infrared spectra, and optical absorption techniques indicated that the glasses are embedded with Ag3PO4, Ag2SeO3, and Zn3(PO4)2 anisotropic crystal phases along with Ag+ ions and Ag0 particles. Dielectric properties, ac conductivity (σac), and dielectric breakdown strength (DBS) are investigated as functions of Ag2O concentration. The results show the maximal concentration of Ag+ ions and Ag0 metallic particles in the sample containing 0.6 mol% of Ag2O. Dielectric parameters and (σac) increase with increasing Ag2O up to 0.6 mol%, while the DBS and electrical impedance decrease. The observed dipolar effects are quantitatively analyzed and possible dipoles are identified. Ionic contribution is predominant up to 0.6 mol% of Ag2O, beyond which the polaronic tunneling phenomenon prevails. These findings indicate that 0.6 mol% of Ag2O is the optimal concentration for using these glass ceramics as solid electrolytes in ionic batteries. Moreover, glass ceramics containing Ag2O beyond 0.6 mol% have exhibited larger polaronic conductivity, hence such glasses can be considered suitable candidates for electrodes in ionic batteries.
Herein, a study on dielectric properties of ZnO–P2O5–SeO2 glass ceramics containing varied contents of silver oxide is presented. From the analysis of the results of these studies, it is concluded that 0.6 mol% of Ag2O is the optimal concentration for using these glass ceramics as solid electrolytes in ionic batteries
In this work we have studied the dielectric properties of Li2O-Nb2O5-P2O5: Ag2O glasses as a function of Ag2O concentration. Auxiliary studies viz., optical absorption, photoluminescence (PL), XPS ...and IR spectra have also been performed on these glasses. IR spectral studies have indicated that the host glass network doped with 1.0 mol% of Ag2O is highly polymerized. Optical absorption and PL studies have clearly exhibited absorption and emission bands due to surface plasmon resonance (SPR). From these studies, the presence of Ag0 -Ag+ clusters is established in the glass network and the concentration of such clusters is found to be the highest in the glass doped with 1.0 mol% of Ag2O. Finally, we have performed extensive studies on dielectric properties viz., dielectric constant, loss, electric moduli, impedance spectra and a.c. conductivity over broad ranges of frequency (0.01 Hz–1 MHz) and temperature (303–513 K). The glasses doped with higher content of Ag2O exhibited higher values of dielectric constant especially at lower frequencies and higher temperatures. The larger contribution from space charge polarization is predicted to be responsible for such higher values. In the glasses doped with low contents of Ag2O (<1.0 mol%) the polaron conductivity (due to the polaronic transfer between Ag0 and Ag+ ions) seemed to be dominant, whereas in the glasses containing more than 1.0 mol% of Ag2O, the ionic conduction (due to the diffusion of Ag+ and Li+ ions) appear to prevail. The impedance diagrams drawn between Z′ and Z″ have further supported the above-mentioned conclusions. From the overall analysis of the results of dielectric properties (including a.c. conductivity) with the aid of experimental results on spectroscopic studies, it is concluded that the glass containing more than 1.0 mol% of Ag2O exhibited predominantly ionic conductivity and hence such glasses may be useful as electrolytes for ionic conducting batteries.
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•Dielectric properties of Li2O-Nb2O5-P2O5: Ag2O glasses were investigated.•Results were analyzed with the aid of data on spectroscopic studies.•Glass with more than 1.0 mol% of Ag2O exhibited predominantly ionic conductivity.•Such glasses may be useful as electrolytes for ion conducting batteries.
This work is focused on the amplification of green (G), orange (O) and NIR (1.5 μm) emissions of Er3+ ions by co-doping with varying contents (traces ≤ 0.1 mol%) of Au2O3 in an exotic PbO-B2O3-SeO2 ...glasses ceramic. The glasses were synthesized by conventional melt quenching method and were crystallized by heat-treating them at crystallization temperature for a period of 24 h. Initial characterization of the samples by means of SEM, XRD, XPS, IR and Raman studies suggested that the post-heated samples are entrenched with poly-crystal grains (with sizes varying from 100 to 500 nm). These studies have also revealed that the concentration of such nano-crystallites is increased with increased content of Au2O3 up to 0.075 mol%. The XRD studies, in particular, have indicated that the glass ceramics are composed of Au2(SeO3)2(SeO4) (crystal phase containing Se ions of mixed valence states) and Au0 nano particles. The XPS studies have also indicated the presence of Se and gold ions in different valence states in these samples. IR and Raman spectra have suggested increased degree of internal chaos in the glass ceramic with increasing concentration of Au2O3. Optical absorption (OA) spectra of Au2O3 doped glass ceramic samples (without Er3+ ions) exhibited a broad band in the visible region identified as surface plasmon resonance (SPR) band of gold metallic particles. The photoluminescence (PL) spectra of these samples exhibited an emission peak due to inter-band transition from sp to d energy bands of Au0 metallic particles. This emission is identified to play a crucial role in enhancing PL emission of Er3+ ions in the visible and NIR regions. Finally, we have recorded optical absorption, photoluminescence spectra and decay profiles of the Er3+ doped (with Au2O3 as co-dopant) glass ceramics. The spectra were characterized using J–O theory and different radiative parameters (viz., transition probabilities, branching ratios, radiative lifetime) of green, orange and NIR emission transitions of Er3+ ions were evaluated. The results indicated a significant reinforcement of green (4S3/2 → 4I15/2), orange (4F9/2 → 4I15/2) and NIR (4I13/2 → 4I15/2) emissions of Er3+ ions due to co-doping with Au2O3. Quantitative analysis of the results of PL emission indicated that 0.075 mol% of Au2O3 is the optimal concentration for achieving the highest quantum yield of these three emissions in this glass ceramic. Additional population of 4S3/2, 4F9/2 and 4I13/2 energy levels of Er3+ ions from the excited state of Au0 metallic particles is found to be the reason for such enhancement of quantum efficiency.
PL spectra of Au metallic particles in PbO-B2O3-SeO2-Er2O3 glass ceramics mixed with different concentrations of Au2O3along with energy scheme of gold particles. Display omitted
•Exotic PbO-SeO2-Er2O3: Au2O3 glass ceramics were synthesized.•Amplification of G, O and NIR emission emissions of Er3+ ions is investigated.•PL results suggested that EA75 sample exhibited the highest efficiency.•Energy transfer from Au0 particles is found to be the reason for such enhancement.
Zinc borate glasses with different concentrations of Nb2O5 were prepared and later were heat treated for prolonged times. Prepared samples were characterized by XRD, SEM, DSC, IR and optical ...transmission spectroscopy techniques. Later, dielectric properties viz., dielectric constant, loss tangent, electric modulii, electrical impedance and a.c. conductivity over wide ranges of frequency and temperature, were investigated as a function of Nb2O5 concentration. Finally, the dielectric breakdown strength was measured in air medium at ambient temperature. The results of characterization techniques viz., XRD, SEM and DSC indicated that multiple crystal grains (with sizes varying from 0.1 to 1 μm) are dispersed in the residual glass phase. The concentration of crystal grains found to increase with increase in Nb2O5 content. The XRD studies have further revealed that the bulk samples are composed of columbite ZnNb2O6 crystal phases. Using generalized gradient approximation (GGA) quantitative information on these crystal phases viz., the lattice parameters, optical band gap and band structure were evaluated. The analysis of results of IR spectral studies have indicated that there is an increasing degree of polymerization of glass network with increase in Nb2O5 content due to the increased connectivity between various structural groups in the glass network. The optical absorption spectra indicated an increase in optical transmittance of the bulk samples with increase in Nb2O5 content. The dielectric parameters are observed to decrease, whereas the dielectric breakdown strength is observed to increase to a large extent due to the crystallization of the glass with the Nb2O5. The increase is attributed to the formation of ZnNb2O6 crystalline phases that contain intertwined ZnO6 and NbO6 structural units. As a whole, zinc borate glasses exhibited a significant increase in the electrical insulating strength due to the crystallization with Nb2O5 as the crystallizing agent. Further, the value of dielectric constant is also found to be the optimal with no dispersion with frequency up to 450 K. Overall, the studied glass‐ceramics meet the necessary physical conditions to be used as insulating layers in the display panels and hence may be considered for such applications.
In this study, we have reported results of the investigation related to the influence of nickel ions on in vitro bio-activity of CaF2–CaO–B2O3–BaO–P2O5 glasses. The studies carried out are, ...degradation studies of the glass samples in SBF for a long time (for about a month), XRD, SEM and spectroscopic properties performed before and after immersion in simulated fluid suggested a thin coating of HAp crystalline grains on the surface of the glasses. IR and Raman spectral studies have further confirmed the formation of HAp layer. Magnitude of fraction of the samples that are degraded in the fluid is evaluated by weight loss and pH of remaining fluid. Degradation results along with characterization studies as a function of concentration of NiO indicated an increasing quantity of HAp deposited on the samples with the rise of NiO quantity up to 0.6 mol%. Spectroscopic investigations have further indicated the nickel ions occupied Oh and Td positions in the glass network. The studies have also suggested Oh occupancy of these ions is dominant in the glass doped with 0.6 mol% of nickel oxide while the fraction of tetrahedral nickel ions is minimal in this glass. The scrutiny of the degradation study results in combination with spectroscopy studies indicated that higher concentration of octahedral nickel ions are preferable for achieving higher quantity of crystalline HAp layer on the surface of the samples while the tetrahedral nickel ions are hindrance in promoting the growth of HAp layer.
•In vitro degradation of NiO doped calcium oxy fluoroboro phosphate glasses is studied.•Bioactivity ability of the glasses is evaluated as function of NiO concentration.•Thin coating of crystalline Ca-HAp is observed on the surface due to immersion in SBF.•0.6 mol% of NiO is optimal concentration for the deposition of high magnitude of HAp.
This work is focused on the evaluation of the free volume space and the concentration of nano-sized cavities trapped in Fe2O3 mixed lead zirconium silicate glass ceramics using positron annihilation ...lifetime spectroscopy (PALS) studies with 22Na (0.1MBq) positron source. Such imperfections are anticipated to have strong bearing on physical characteristics of the glass ceramic. The glasses of a particular composition viz., 36PbO–4ZrO2–(60–x)SiO2: xFe2O3 (0 ≤ x ≤ 0.5 in the intervals of 0.1) were synthesized by traditional melting and quenching techniques. The lifetime of the positrons measured in these samples is found to be strongly reliant on the content of Fe2O3. The results have suggested the increased fraction of free volume imperfections (fv), and radius of the cavities (R) with increase of Fe2O3 content from 0.2 to 0.5 mol%. The spectroscopic studies of these samples indicated that iron ions predominantly existed in Fe3+ state and occupied octahedral positions with FeO6 structural units, acted as modifiers and induced several imperfections. The estimated maximal concentration of imperfections in the glass ceramic sample F5 by PALS studies is attributed to such reasons. The inferences drawn from PALS studies regarding the concentration of defects in these samples are found to be in agreement with the results of third harmonic generation (THG) studies and conductivity studies.
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