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This investigation consists of results of the studies on dielectric properties and a.c. conductivity of Li2O-Ga2O3-SiO2 (LGS) glass with 2.0 mol% of Cr2O3, MoO3, WO3 across 0.01 Hz to 1 MHz and 20 °C to 240 °C. Structural analysis using optical absorption and IR spectra indicated dopant ions predominantly in Cr3+, Mo6+/Mo5+, W6+ states, and occupied Td and Oh positions. Dielectric constant and conductivity were found to be the maximal for LGSMo glass, with the lowest impedance, while LGSCr glass exhibited the opposite trend. From the analysis of dipolar relaxation effects probable dipoles were identified in each glass. Studies on conductivity revealed that contribution of ionic components is very low and a substantial polaronic contribution in LGSMo glass, whereas, LGSCr glass showed a larger ionic component, specifically Li+ ion diffusion and hence more useful material for solid-state batteries with respect to the other two glasses. [ABSTRACT FROM AUTHOR]

PbO--MoO3--B2O3 glasses containing various proportions of NiO (ranging from 0 to 1.0 mol %) have been prepared. A number of methods viz., differential thermal analysis, spectroscopic (IR and UV-Vis optical absorption, and ESR spectra) and dielectric properties (ε' tan δ, a.c. conductivity &etch;ac over a range of frequencies and temperatures) of these glasses has been employed in studies. The results of differential thermal analysis suggest a high glass forming ability for the glass containing 0.6 mol % of NiO. The studies of UV-Vis and IR spectra show that nickel ions occupy both tetrahedral and octahedral positions in the glass network with the dominance of the tetrahedral positions when the concentration of NiO is below 0.6 mol % in the glass matrix. The analysis of the results of studies of dielectric properties reveals that there is an increase in the rigidity and the dielectric breakdown strength of the glass when the concentration of NiO is around 0.6 mol %. [ABSTRACT FROM AUTHOR]

Abstract: ZnO–ZnF2–B2O3 glasses were synthesized and crystallized with different concentrations of TiO2 (0–0.5mol% in the steps of 0.1) as nucleating agents. The prepared samples were characterized by XRD, SEM and DSC. These studies have revealed that the samples contain well defined randomly distributed crystalline phases with the complexes of Ti4+ and Ti3+ ions. Optical absorption studies have indicated that a part of titanium ions exist in Ti3+ state in the bulk samples. Dielectric properties were also studied over broad ranges of temperature and frequency of the glass ceramics. The obtained results were analyzed in terms of different polarization mechanisms. The dielectric break down strength of titled glass ceramics was also measured at room temperature in the air medium. The break down strength is found to decrease with the concentration of nucleating agent. The analysis of the results of dielectric properties indicated a decrease of insulating strength of the glass ceramic samples with increase of TiO2 content. [Copyright &y& Elsevier]

Abstract: Li2O–WO3–P2O5 glasses containing small concentrations of Ag2O from 0 to 1 mol% were prepared. A number of studies viz., chemical durability, dielectric studies (constant ɛ′, loss tan δ, a.c. conductivity σ ac over a range of frequency and temperature), spectroscopic (infrared, optical absorption ESR spectra) and magnetic susceptibility studies of these glasses, have been carried out. The interesting variations observed in all these properties with the concentration of Ag+ ions have been analyzed in the light of different oxidation states and environment of tungsten ions in the glass network. [Copyright &y& Elsevier]

This investigation is devoted to study the influence of CoO concentration on dielectric characteristics of a heavy metal oxide glass system viz., lead bismuth silicate. The auxiliary spectroscopic studies have indicated progressive increase of the fraction of tetrahedral (T d) divalent cobalt ions in the glass structure as the concentration of CoO is gradually raised. Dielectric parameters measured in the wide range of frequencies and temperatures showed a lowering trend with CoO content; such result is attributed to the growing presence of Co2+ (T d) ions that participate in the glass structure that would obstruct the migration of charge carriers towards electrodes. Electric moduli variations have exhibited dipolar relaxation effects. Co2+ (O h) and Bi3+ ions were predicted to be responsible for these effects. A. c. conductivity and (N(E F)) the concentration of disordered states exhibited decreasing trend, whereas activation energy for a.c. conduction showed increasing trend with CoO content. Impedance plots drawn as a function of CoO concentration suggested the increasing impedance of the glasses. The quantitative analysis of results of dielectric studies suggested that Co ions prevailingly took part in the glass network in T d locations, facilitated the growing polymerization of the glass structure and thereby increased stiffness of the glass network against the applied electrical filed or increased the electrical insulating strength of the glasses. Finally, it is concluded that these glasses may be considered for applications as transparent electrical shielding sheets in display panels. • Influence of CoO on dielectric properties of PbO‒Bi 2 O 3 ‒SiO 2 glass system is reported. • Spectroscopic studies indicated hike in Co2+ (Td) ion concentration with CoO content. • Dielectric parameters and conductivity exhibited a decreasing trend with CoO content. • Enhanced linkages among various SiO 2 groups improved insulating strength of the glass • These glasses may be useful for applications as shielding sheets in display panels [ABSTRACT FROM AUTHOR]

• As 2 O 3 glass ceramics mixed with SeO 2 and TeO 2 and doped with Ag 2 O were prepared. • Characterization indicated entrenchment of Ag 3 AsO 4 phase and Ag0 MPs in the samples. • ε′, σ ac exhibited increase with Ag 2 O beyond 0.5 mol% due to increase of Ag0 MPs. • σ ac variation with Ag 2 O content was analyzed using different conduction mechanisms. • Samples with > 0.5 mol% of Ag 2 O are preferable to achieve high ionic conductivity. In this work, As 2 O 3 glasses mixed with two chalcogenide oxides (SeO 2 and TeO 2) and doped with varied contents of Ag 2 O were prepared and heat-treated. Characterized by various techniques suggested that these glasses were embedded with Ag 3 AsO 4 crystal phases and Ag0 metallic particles (MPs). Later, different dielectric parameters viz., dielectric constant (ε′), electric modulus (M), electrical impedance (Z). conductivity a.c. conductivity a.c. conductivity and σ ac were measured over broad frequency (ω) and temperature (T) regions. Observed decrement in ε′, σ ac with Ag 2 O up to 0.5 mol% was understood due to the increased fraction of As5+ ions that occupy network-forming positions with AsO 4 units. The observed increase of these parameters with Ag 2 O beyond 0.5 mol% was attributed to the growing fraction of Ag0 MPs that acted as modifiers. The variation of σ ac with Ag 2 O content was analyzed using different conduction mechanisms. Overall, it is predicted that greater than 0.5 mol% of silver oxide is preferable for achieving better ionic conductivity in these glasses [ABSTRACT FROM AUTHOR]

In this work we have synthesized ZnO–Ta 2 O 5 –B 2 O 3 glass ceramics with different concentrations of Ta 2 O 5 . The prepared samples were characterized by XRD, SEM and DSC techniques. The results of these studies indicated that the samples are embedded with well defined randomly distributed crystalline phases with Zn 3 Ta 2 O 8 as the predominant one. The volume fraction of the crystallinity seemed to be increasing with increase of Ta 2 O 5 content. The lattice parameters of this crystal phase and the optical band gap were evaluated theoretically using generalized gradient approximation (GGA) and also the local density approximation (LDA). The obtained results were compared with experimental values. The analysis of the results of IR and Raman spectroscopic studies indicated that the degree of polymerization of glass network increased with increase in the concentration of crystallizing agent (Ta 2 O 5 ) up to 3.0 mol%. To evaluate the insulating strength of the glass ceramics we have studied the dielectric properties over broad ranges of frequency (100 Hz −1 MHz) and temperature (100–370 K) and also dielectric breakdown strength. The quantitative analysis of these results coupled with the results of spectroscopic studies indicated that the glass crystallized with 3.0 mol% of Ta 2 O 5 possesses high insulating strength. [ABSTRACT FROM AUTHOR]

• Pb 3 O 4 mixed Li 2 O-SiO 2 :Au 2 O 3 glasses were synthesized and characterized. • Different dielectric parameters viz., ε ′ , M, Z and σ a c were measured as functions of Au 2 O 3 content. • ε′ was decreased with Au 2 O 3 upto 0.04 mol% due to growing presence of PbO 4 units. • Observed dipolar relaxation effects were evaluated using Cole-Cole diagrams. • σ a c exhibited a decreasing trend with Au 2 O 3 content up to 0.04 mol%. • Overall, the presence of red lead was found to reduce the conductivity in these glasses. Studies on dielectric properties viz., ε′ (dielectric permittivity), M, Z and σ ac as functions of frequency and temperature (over wide ranges), of glasses/glass-ceramics give quantitative information on their insulating character. Such studies are also useful for understanding structural aspects of these glasses to a great extent. In this work Pb 3 O 4 mixed Li 2 O-SiO 2 :Au 2 O 3 glasses were synthesized and heat-treated. Analysis of the results of various characterization techniques indicated increased degree of internal augmentation between various structural groups of the glass network. Observed decrease of ε′ with Au 2 O 3 content up to 0.04 mol% was attributed to the decreased magnitude of space charge polarization due to growing presence of PbO 4 units in the glass network. Dipolar relaxation effects of these samples were evaluated using Cole-Cole plots. Variation of conductivity with Au 2 O 3 concentration was analyzed using polaronic tunneling model. Conclusions of these results were found to be in in concurrence with spectroscopic studies. Overall, the presence of Pb 3 O 4 caused reduction the conductivity of these glasses. [ABSTRACT FROM AUTHOR]

• PbO-B 2 O 3 -SeO 2 :Er 2 O 3 glass ceramics added with traces of Au 2 O 3 were synthesized. • Characterization studies indicated increasing fraction of defects with Au 2 O 3 content. • Dielectric parameters ε′ , M , Z and σ ac are measured in broad ω temperature T ranges. • ε′ is observed to increase with Au 2 O 3 content due to the space charge polarization. • Mechanism of conduction is analyzed using polaronic tunneling model middle ω region. The variations of M′ and M″ with frequency and temperature of glass ceramic sample EA 75. [Display omitted] The glass ceramics of the composition PbO-B 2 O 3 -SeO 2 :Er 2 O 3 (PBSE) doped with small concentrations of Au 2 O 3 were synthesized. The results of detailed studies on various characterization techniques and also different spectroscopic investigations suggested that these glass ceramics are entrenched with Au 2 (SeO 3) 3 crystal phases and Au0 metallic particles (MPs). These studies further revealed increasing concentration of [SeO 3 ]2- groups and Au0 metallic particles with the increase of Au 2 O 3 content upto 0.075 mol%. Such [SeO 3 ]2- groups are predicted to induce structural imperfections in the glass ceramic. Optical absorption (OA) and photoluminescence (PL) spectral studies also indicated increasing concentration of imperfections with increase of Au 2 O 3 content. The dielectric viz, dielectric permittivity (ε′), electrical modulus (M) , electrical impedance (Z) and a.c. conductivity (σ ac) spectra in the frequency (ω) region 4 Hz to 8 MHz and in the temperature (T) region 303–633 K of these glass ceramic samples were measured as functions of Au 2 O 3 concentration. The dielectric permittivity (ε′) exhibited an increasing trend with Au 2 O 3 concentration and it is ascribed to the increase in the magnitude of the space charge polarization (scp) due to the increase in the concentration of structural defects induced by [SeO 3 ]2- units and Au0 metallic particles. The plots of electric modulus (M) with frequency and temperature exhibited dipolar relaxation phenomena. Such effects were analyzed further using Cole-Cole diagrams and the possible dipoles responsible for these effects were identified. A.C. conductivity (σ ac) exhibited increasing trend with the concentration of Au 2 O 3 (up to 0.075 mol%) and such increase is attributed to the polaronic exchange between different structural groups of selenium oxide. The conduction mechanism is analyzed using polaronic tunneling effect in the middle frequency and high temperature regions, whereas in the lower temperature region QMT model seems to be applicable. Conclusions drawn from dielectric properties were found to be well in accordance with the results of spectroscopic properties. [ABSTRACT FROM AUTHOR]

Abstract: Sodiumsulpho borophosphate glasses with composition (40− x)Na2SO4–30B2O3–30P2O5: xMnO with x ranging from 0 to 5.0mol% were manufactures. Dielectric spectra have been studied over a wide frequency range of 102–105 Hz and in the temperature range within 30–250°C. The valance states of manganese ions and their ligand coordination in the glass network have been investigated using optical absorption, luminescence and ESR spectroscopy. The analysis of the these results has indicated that the manganese ions exist both in Mn2+ as well as in Mn3+ states and occupy prevailingly octahedral positions and serve as modifiers similarly to Na+ ions The values of dielectric parameters (dielectric constant, ε′(ω), loss tan δ and ac conductivity, σac) were found to increase with increasing MnO content. They play a role of modifiers similarly to Na+ ions, create bonding defects and free ions viz., [SO4]2−, [POO1/2O2]2−, [POO0/2O3]3–, Na+ and (NaSO4)−. The migration of these charge carriers would build up space charge polarization and may be responsible for the enhanced dielectric parameters. The ac conductivity also is enhanced with increasing MnO content. The mechanism responsible for such increase is well explained based on the modifying action of Mn2+ ions. [Copyright &y& Elsevier]

Abstract: A series of Na2SO4–B2O3–P2O5 glasses doped with different concentrations of TiO2 (0 to 1.0mol%) have been synthesized. Dielectric properties (over a range of frequency and temperature) and a variety of spectroscopic (optical absorption, IR, Raman and ESR) properties of these glasses have been investigated. The values of dielectric parameters viz., dielectric constant, loss and ac conductivity at any frequency and temperature are observed to increase with the concentration of TiO2. The optical absorption and ESR spectral studies have pointed out that a part of titanium ions do exist in Ti3+ state in addition to Ti4+ state especially in the samples containing higher concentration of TiO2. The increase of dielectric constant with the concentration of TiO2 is explained on the basis of space charge polarization due to increasing concentration of various bonding defects in the glass network. The dielectric relaxation effects exhibited by these glasses are quantitatively analyzed by pseudo Cole–Cole method and the spreading of relaxation times is established. The ac conductivity is observed to increase with increasing content of TiO2, the mechanism responsible for such increase is well explained based on the modifying action of Ti3+ ions. [Copyright &y& Elsevier]

Abstract: LiI–AgI–B2O3 glasses mixed with different concentrations of V2O5 (ranging from 0 to 1.0mol%) were prepared. Electrical and dielectric properties over wide ranges of frequency (10−2–107 Hz) and temperature (173–523K) have been studied. Additionally spectroscopic properties viz., optical absorption and ESR spectra have been investigated. The optical absorption and ESR studies have revealed that vanadium ions do exist in both V4+ and V5+ states and the redox ratio is the highest in the glasses containing 0.8mol% of V2O5. The results of conductivity measurements have indicated that there is a mixed conduction (both ionic and electronic). The ionic conduction seems to be dominant over polaron hopping only in the glasses containing V2O5 more than 0.8mol% of V2O5. The impedance spectra have also indicated that the conduction is predominantly polaronic in nature. The frequency and temperature dependence of the electrical moduli as well as dielectric loss parameters have exhibited relaxation character attributed to the vanadyl complexes. The relaxation effects have been analyzed by the graphical method and from this analysis it has been established that there is a spreading of relaxation times. The results have been further discussed quantitatively in the light of different valance states of vanadium ions with the aid of the data on spectroscopic properties. [Copyright &y& Elsevier]

• Influence of V 2 O 5 on dielectric features of bismuth silicate glasses is investigated. • Spectroscopic studies revealed increasing disorder of the glass network with V 2 O 5 content. • σ ac exhibited maximal value for the glass with 0.6 mol% of V 2 O 5 content. • In the glasses doped with >0.3 mol% of V 2 O 5 ionic contribution to σ ac is dominant. V 2 O 5 doped lead bismuth silicate glasses were prepared by melt quenching technique. Initially, the spectroscopic investigations viz., optical absorption (OA) and EPR spectral studies were performed; the results of these studies suggested reduction of a part of V5+ ions into V4+ ions (that are identified to form vanadyl complexes viz., VO2+). The results further indicated the largest concentration of such complexes in the glass doped with 0.6 mol% of V 2 O 5. Infrared spectral (IR) results suggested a progressive disintegration of the augmented glass network with increase of V 2 O 5 concentration beyond 0.3 mol%. Later, extensive investigations on dielectric properties were carried out. Values of dielectric permittivity, ε′(ω), loss tangent and a.c. conductivity, σ ac , observed to be minimal for the glass containing 0.3 mol% of V 2 O 5 (V 3 glass) and found to be increased for further increase of V 2 O 5 content at any frequency and temperature. The electric moduli components exhibited dipolar relaxation effects. Relaxation time τ for dipoles estimated from the spectra of electric moduli showed a decreasing trend as the V 2 O 5 content increased up to 0.3 mol% and beyond that τ is found to be increased. The complexes of V4+ and Bi3+ ions with oxygen ions were predicted to be the possible dipoles responsible for the dipolar effects. A.c. conductivity variation with V 2 O 5 concentration indicated the minimum for V 3 glass and exhibited increasing trend as the content of V 2 O 5 raised from 0.3 to 0.6 mol%. Quantitative analysis of this result indicated polaronic contribution to the conductivity (ascribed to mutual transfer of polarons between V4+and V5+ ions) is prevalent in these glasses. [ABSTRACT FROM AUTHOR]