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This study consists of comprehensive investigations on dielectric permittivity (ε′), electric moduli (M′, M″), impedance (Z), and conductivity (σac) spectra over broad regions of frequency and temperature of lead zirconium silicate glass ceramics mixed with different concentrations of Fe2O3. The observed increase in dielectric permittivity with the content of Fe2O3 is attributed to the increasing presence of iron ions in octahedral positions. Electric moduli plots with frequency (ω) and temperature (T) exhibit dipolar effects. These effects are quantitatively analyzed by Cole–Cole plots; the analysis indicates the distribution of relaxation times. Probable dipoles for these effects are identified and discussed. AC conductivity (σac) shows a rising trend with an increase in Fe2O3 beyond 0.2 mol%, and this increase is attributed to the polaron exchange among Fe2+ and Fe3+ ions. The conduction mechanism is well explained using a polaron tunneling model in the middle‐frequency and high‐temperature regions. [ABSTRACT FROM AUTHOR]

This study is aimed to identify the role of Fe2O3 in enhancing the efficiency of THG beam of Nd:YAG laser in lead zirconium silicate glass ceramics. The PbO–ZrO2–SiO2:Fe2O3 glass ceramics were synthesized by heat-treating the glasses for a prolonged time. XRD and SEM studies were performed to identify different crystalline phases in the samples. The SEM pictures have shown the presence of multiple crystallites of size in the range 0.1–0.6 µm, while characterization by XRD technique indicated the glass ceramic samples consist of perovskite Pb2FeIII2O5, FeII2SiO4, crystal phases. These studies have also demonstrated that there is an enhancement in the concentration of Fe3+ (Oh) crystalline phases with increasing quantity of Fe2O3 in the samples. Spectroscopic investigations (viz., IR and optical absorption) have further reinforced the above result and additionally indicated an increased degree of internal chaos in the material. The intensity of third harmonic generation (THG) beam of Nd:YAG laser (λ = 1064 nm) measured in the reflected regime after the pre-photopolarization of the samples indicated the largest intensity for the samples containing the highest concentration of Fe2O3. Thorough analysis of these results indicated that the tilted glass samples heat-treated with 0.5 mol% of Fe2O3 have significant chaotic internal structure and paved the way for obtaining intense THG signal with minimal phonon losses. Hence, such glass ceramics are predicted to be useful materials in the design of different optoelectronic devices. [ABSTRACT FROM AUTHOR]

The objective of this work is to explore the Ag ion concentration dependence on structural and dielectric characteristics of Na 2 O Sb 2 O 3 : Ag 2 O glass ceramics. The prepared glass ceramics were characterized by XRD, XPS, SEM, TEM, EDS and DSC techniques. These studies have revealed that the samples are composed of multiple crystal grains entrenched in the remnant amorphous phase. The IR and Raman spectroscopic studies indicated increasing degree of polymerization of the glass network with increase of Ag 2 O concentration up to 0.1 mol%. This is attributed to increasing concentration of tetrahedral Sb5+ ions that take part in the glass network forming. Optical absorption spectra have exhibited surface plasmon resonance (SPR) band in the wavelength region 400–450 nm. Quantitative studies on dielectric properties were performed over wide ranges of frequency and temperature and the variations of these properties with the concentration of Ag 2 O are discussed in the light of various polarization processes. Dipolar orientational effects exhibited by electric moduli spectra suggested multiple relaxation times for electric dipoles. The observed decrease of A.C. conductivity (that contains both ionic and polaronic components) with increase of Ag 2 O content up to 0.1 mol% is attributed to the increasing degree of polymerization of the glass network that hinders the migration of charge carriers. The polaronic conduction is understood due to exchange of polarons between Sb3+ ‒ Sb5+ and Ag0 Ag+ ions, while ionic conductivity is predicted due to transport of monovalent silver and Na+ ions. A changeover of polaronic to ionic conductivity seemed to take place at about 0.1 mol% Ag 2 O. Impedance plot for sodium antimonate glass crystallized with 0.1 mol% of Ag 2 O. Image 1 • Structural and dielectric properties of Na2O Sb2O3: Ag2O glass ceramics investigated. • Structural studies indicated samples contain Sb3+, Sb5+, Ag+, Ag0 crystal phases. • Samples with >0.1 Ag mol% exhibit larger ionic conductivity. • Polaronic component of a.c. conductivity is prevailed up to 0.1 mol% of Ag 2 O. [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]

• 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]

• With sound velocities elastic constants of Au 2 O 3 : PBSE glass-ceramics are estimated. • These coefficients observed to be decreasing with the concentration of Au 2 O 3. • Such decrease is attributed to the increasing concentration of Au0 MPs. • The results are found to be consistent with spectroscopic and PAL studies. Various elastic coefficients of Au 2 O 3 doped PbO-B 2 O 3 -SeO 2 :Er 2 O 3 (PBSE) glass ceramics were evaluated as functions of Au 2 O 3 content using ultrasonic velocity measurements. The elastic coefficients and micro-hardness showed a decreasing tendency with the concentration of Au 2 O 3. Such decrease is attributed to the increasing concentration of gold metallic particles and [SeO 3 ]2− groups that acted as modifiers and induced imperfections in these samples. Obtained results were observed to be consistent with the conclusions drawn from spectroscopic studies that include X-ray photoelectron spectroscopy (XPS), infrared (IR), photoluminescence (PL) and positron annihilation (PAL) spectroscopy studies. Overall, these studies have revealed that even though, the presence of gold metallic particles is preferable for achieving superior luminescence and electrical properties, presence of such particles caused to decrease the elastic coefficients and micro-hardness of these glass ceramics. However, when the concentration of Au 2 O 3 is increased beyond 0.075 mol%, we have observed a slight increase of elastic coefficients and micro-hardness. [ABSTRACT FROM AUTHOR]

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 Au 2 O 3 in an exotic PbO-B 2 O 3 -SeO 2 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 Au 2 O 3 up to 0.075 mol%. The XRD studies, in particular, have indicated that the glass ceramics are composed of Au 2 (SeO 3) 2 (SeO 4) (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 Au 2 O 3. Optical absorption (OA) spectra of Au 2 O 3 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 Au 2 O 3 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 (4S 3/2 → 4I 15/2), orange (4F 9/2 → 4I 15/2) and NIR (4I 13/2 → 4I 15/2) emissions of Er3+ ions due to co-doping with Au 2 O 3. Quantitative analysis of the results of PL emission indicated that 0.075 mol% of Au 2 O 3 is the optimal concentration for achieving the highest quantum yield of these three emissions in this glass ceramic. Additional population of 4S 3/2 , 4F 9/2 and 4I 13/2 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-B 2 O 3 -SeO 2 -Er 2 O 3 glass ceramics mixed with different concentrations of Au 2 O 3 along with energy scheme of gold particles. Image 1 • Exotic PbO-SeO 2 -Er 2 O 3 : Au 2 O 3 glass ceramics were synthesized. • Amplification of G, O and NIR emission emissions of Er3+ ions is investigated. • PL results suggested that EA 75 sample exhibited the highest efficiency. • Energy transfer from Au0 particles is found to be the reason for such enhancement. [ABSTRACT FROM AUTHOR]