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Abstract: Hybrid borate glasses containing a series of Al(III)Porphyrins were prepared by rapid melt quench technique at 230°C. The hybrid glass samples were characterized by X-ray diffraction, optical absorption, steady state and time resolved fluorescence emission. Upon exposure to UV light at 260nm, the glass samples exhibit strong blue emission and red emission at 365nm. The appearance of large stokes shift (Δυ) and enhanced S 2 → S 0 emission at ∼495nm indicates that structure of Al(III)Porphyrins were inherently modified in glass matrix. Time resolved fluorescence of the hybrid glasses shows three exponential decay with τ 1 =0.11–0.59ns, τ 2 =3.13–3.95ns and τ 3 =8.13–9.56ns. In the present study, we investigate the influence of glassy environment on the photophysical properties and the structure of Al(III)Porphyrins in borate glass was modeled through DFT calculations. [Copyright &y& Elsevier]

Lithium borate glasses of composition 30Li 2 O–10MO–59B 2 O 3 :1Pr 2 O 3 (MO=ZnO, CaO and CdO) were prepared by a conventional melt quenching method. The amorphous nature of these glasses was confirmed by X-ray diffraction. Characterization of these glasses was carried out by differential scanning calorimetry and infrared spectra. Optical absorption and photoluminescence spectra of these glasses were investigated. Judd–Ofelt intensity parameters Ω λ ( λ =2, 4, and 6) are evaluated from the intensities of various absorption bands of optical absorption spectra. From this theory various radiative properties like transition probability A , branching ratio β r , the radiative lifetime τ R , and the stimulated emission cross-section σ P for various emission levels of these glasses have been determined and reported. The relationship between the structural modifications and luminescence efficiencies of all the three glasses is explained. After X-ray irradiation on these glasses, the thermoluminescence emission properties were also studied. The thermoluminescence studies indicate that CdO modified glass gives out the maximum thermoluminescence light output among the three glasses studied. [ABSTRACT FROM AUTHOR]

Abstract: 20ZnF2–30As2O3–(50−x)TeO2:xNiO (0≤x≤2.0) glasses were synthesized. The glasses were characterized by X-ray diffraction, scanning electron microscopy, EDS and DSC techniques. A variety of properties, i.e. optical absorption, infrared, magnetic susceptibilities and dielectric properties (constant ϵ′, loss tan δ, a.c. conductivity σac over a wide range of frequency and temperature) of these glasses have been carried out. The analysis of results of all these studies has indicated that the nickel ions occupy both octahedral and tetrahedral positions and the gradual increase of NiO content in the glass matrix causes growing proportions of Ni2+ ions that occupy octahedral positions. The luminescence spectra of these glasses have exhibited a broad emission band in region 1200–1450nm identified due to 3T2(3F)→ 3A2(3F) octahedral transition of Ni2+ ions. The luminescence efficiency and cross section have been found to be the highest for the glass containing highest concentration of NiO. Finally it is concluded that the higher the concentration of octahedrally positioned Ni2+ ions, the higher is the luminescence efficiency. [Copyright &y& Elsevier]

Abstract Stupendous progress in realizing optical materials is due to extreme strides which were adapted so far in understanding optical properties of materials. Keeping this in view a series of Bismuth Borosilicate glasses modified with strontium and doped with various concentrations of Sm3+ (SrO Bi 2 O 3 B 2 O 3 SiO 2 Sm 2 O 3) have been prepared by classical melt quench technique. These glasses were structurally characterized by XRD to confirm amorphous nature. Vibration mode analysis of samples has been analyzed by infrared transmission spectroscopy. This paper show cases various optical phenomena such as absorption and luminescence which plays a key role in design of engineered optical materials. To understand absorption, optical excitation, emission and time decay process optical spectroscopy measurements were done. Judd-Ofelt (JO) theory was employed to determine intensity parameters Ω λ=2,4,6 for symmetry of ligand environment existing among Sm3+ ions. From emission spectra various radiative parameters like transition probability (A r), branching ratios (β r) and radiative time were determined. Emission bands of 4G 5/2 → 6H 5/2 (560 nm), 4G 5/2 → 6H 7/2 (599 nm) 4G 5/2 → 6H 9/2 (636 nm) and 4G 5/2 → 6H 11/2 (708 nm) have been recorded with excitation at 401 nm. Above all emission wavelengths 599 nm is more intense and has shown a bright orange emission. Among four emission bands corresponding to 4G 5/2 → 6H 7/2 transition in emission spectra shows high (σ E) peak stimulated emission (22.85 × 10−22 cm2) and optical gain (O.G) is (28.33 × 10−25 cm2s) assure optoelectronic applications. The life time τ exp of excited level 4G 5/2 was determined through decay and non-exponential decay curves. Inokuti-Hirayama model was used to fit non exponential curve for the analysis of luminescence quenching, quantum efficiency (96%), transfer mechanism of energy among Sm3+ ions to ensure Laser applications. CIE colour chromaticity coordinates of present Sm3+ doped glasses also suggest the synthesized glasses are suitable improvement of orange-red lasers. Graphical abstract Image 1 Highlights • Bismuth Borosilicate strontium glasses doped with Sm3+ by melt quench technique. • Optical studies were done through OA, PL and time decay measurements. • PL and CIE coordinates shows bright orange emission. • High peak stimulated emission and optical gain assure optoelectronic applications. • Inokuti-Hirayama model was used to fit non exponential curve for energy transfer. [ABSTRACT FROM AUTHOR]

Abstract Glass ceramics of the composition PbO Al 2 O 3 TeO 2 GeO 2 SiO 2 doped with CoO (ranging between 0 and 1.0 mol %) were prepared by melt quenching technique followed by heat treatment. The techniques such as XRD, SEM, EDS and DTA were employed for the characterization of the prepared samples. Conventional spectroscopic studies viz., optical absorption, photoluminescence, FTIR and Raman were also performed on these samples. The optical absorption spectra of the titled glass ceramics exhibited two principal absorption bands, one at about 594 nm and the second one consisting of multiplets with the meta centre at about 1455 nm ascribed to the 4A 2 (4F) → 4T 1 (4P) and 4A 2 (4F) → 4T 1 (4F) transitions of tetrahedrally coordinated Co2+ ions, respectively. Besides these, the spectra also exhibited two feeble bands at about 532 and 643 nm which are the characteristics of octahedrally coordinated Co2+ and Co3+ ions, respectively. Using Tanabe Sugano diagram the crystal field splitting parameter Dq, Racah parameters B, C and nephelauxetic ratio, β were evaluated for Co2+ ions. The photoluminescence spectra of the titled glass ceramics have exhibited two broad emission bands at 628 and 870 nm ascribed to 4T 1 (4P) → 4A 2 (4F) and 4T 1 (4P) → 4T 2 (4F) tetrahedral transitions of Co2+ ions, respectively. FTIR and Raman spectra of the titled samples exhibited various asymmetrical and symmetrical vibrational bands due to viz., silicate, germanate, PbO 4 , PbO 6 , AlO 6 , TeO 4, TeO 3 and CoIII O vibrations in the glass ceramic matrix. The spectroscopic investigations on the titled glass ceramics have revealed that if CoO is present in small quantities the cobalt ions predominantly occupy the octahedral sites in the glass network, whereas the tetrahedrally coordinated Co2+ ions are found to increase if the concentration of nucleating agent CoO is gradually increased up to 1.0 mol%. As a result the degree of depolymerization of the glass network decreases which in turn enhances its rigidity with increasing the concentration of nucleating agent CoO. From these investigations we report that the glass ceramics doped with 1.0 mol% of CoO are suitable for insulating devices as well as for photonic devices. Graphical abstract Optical absorption spectra of PbO Al 2 O 3 TeO 2 GeO 2 SiO 2 : CoO glass ceramics and the pre-heated samples viz. , Co2, Co10. Image 1 Highlights • PbO Al 2 O 3 TeO 2 GeO 2 SiO 2 : CoO glass ceramics were prepared by melt quenching and heat treatment. • Prepared samples were characterized by XRD, SEM, EDS and DTA. • Absorption bands of the samples indicated the cobalt ions exist in Co2+ and Co3+ state. • Photoluminescence spectra of the samples exhibited emission bands at 628 and 870 nm. • Samples doped with 1.0 mol% of CoO are suitable for insulating and photonic devices. [ABSTRACT FROM AUTHOR]

Abstract Trivalent europium ions doped yttrium alumino bismuth borosilicate glasses (YABiBS) of the composition are synthesized by the melt - quenching method. The structural, thermal and spectral properties of the prepared glasses have been investigated by XRD, EDS, FT-IR, DTA, optical absorption, photoluminescence and decay profiles. XRD indicated the amorphous nature of the samples. From the DTA traces thermal Parameters like ΔT, S and H are evaluated to verify the thermal stability of the titled glasses. FTIR spectra exhibited bands due to various fundamental vibrational units of borate and silicate groups. The optical absorption spectra exhibited the bands due to 7F 0 → 5G 4 , 7F 0 → 5L 6 , 7F 0 → 5D 2 , 7F 0 →7F 6 , and 7F 1 → 7F 6 transitions of Eu3+ ions. In addition the absorption spectra also exhibited a band due to 1S 0 → 1P 1 transition of Bi3+ ions. From the absorption spectra, the optical band gap and Urbach energies and also nephelauxetic ratios were evaluated. The emission spectra (excited at 392 nm) exhibited five luminescence bands at 577, 590, 612, 651 and 700 nm assigned to 5D 0 → 7F 0 , 5D 0 → 7F 1 , 5D 0 → 7F 2 , 5D 0 → 7F 3 , and 5D 0 → 7F 4 transitions of Eu3+ ions, respectively. The absorption and emission spectra were characterized using Judd-Ofelt (J-O) theory and radiative parameters viz. , radiative transition probability (A R), branching ratio (β R), and luminescence quantum efficiency (η), radiative life time (τ), stimulated emission cross-section (σ P E) were evaluated. The values of radiative parameters are found to be the highest for the transition 5D 0 →7F 2 of 0.6mol% Eu3+ doped YABiBS glass (BE0.6). The co-doping of Bi3+ ions (10.0mol %) caused a substantial enhancement (nearly three times) in the intensity of this red emission. These results suggested the energy transfer between Bi3+ ions and Eu3+ ions. The energy transfer efficiency has been explained in terms of structural modifications taking place in the glass network. Highlights • Eu3+ doped YABiBS glass with and without Bi 2 O 3 was prepared by using melt-quenching method. • Enhancement of the red intense emission transition (5D 0.→7F 2) of Eu3+ sensitized by Bi3+ for red laser applications. • Thermal Parameters calculated from DTA curves shows thermal satiability of glasses to develop the optical fibre devices. • The decrease in the optical band gap represents the increase in NBO's. ΔE changes inversely with the optical band gap. [ABSTRACT FROM AUTHOR]

Abstract This work consists of studies on the influence of thermally resistant transition metal oxides (TMO) viz. , Ta 2 O 5 , Nb 2 O 5 and ZrO 2 on orange emission and NIR emission (1.3 μm) of Pr3+ ions in zinc borate glasses. Glasses of the composition 40ZnO–2Ta 2 O 5 /2Nb 2 O 5 /2ZrO 2 –56B 2 O 3 : 2Pr 2 O 3 were synthesized by melt quenching technique. Optical absorption (OA), photoluminescence (PL) emission (in the wavelength region 500–2500 nm at λ exc = 443 nm) and decay profiles of the two of the prominent transitions viz., 3P 0 → 3H 6 and 1G 4 → 3H 5 of Pr3+ ions were recorded. The spectra were analysed using standard J–O calculations and various radiative parameters associated with prominent transitions were estimated. Intensity of PL bands exhibited substantial increase due to addition of Ta 2 O 5 , Nb 2 O 5 and ZrO 2 to the host glass. Among the three studied glasses, ZrO 2 mixed glasses exhibited the highest luminescence output. All the radiative parameters including quantum efficiency are observed to be the largest for ZrO 2 mixed glasses. The results of IR spectral studies were also used for the analysis of emission spectra. The analysis indicated the degree of structural variations in the vicinity of luminescent Pr3+ ions is different due to addition of different transition metal oxides and such variations are found to be responsible for the changes in the PL output. Since a substantial improvement of PL emission corresponding to 1G 4 → 3H 5 transition is observed due to the admixing of TMOs, these glasses may be considered as the favourable candidates for the applications in telecommunications. Additionally, the emission in the green spectral region (which is predicted to be feeble under normal conditions) in the PL spectrum of Pr3+ ions is also found to be considerably increased and it is attributed to the transfer of energy from ZnO to Pr3+ ions in this region. Research Highlights • Glasses of the composition 40ZnO–2Ta 2 O 5 /2Nb 2 O 5 /2ZrO 2 –56B 2 O 3 : 2Pr 2 O 3 were synthesized. • Optical absorption, PL spectra in vis-NIR regions and decay profiles were recorded. • PL output found to be substantially increased due to addition of Ta 2 O 5 /Nb 2 O 5 /ZrO 2. • These glasses are useful in telecommunications because of enriched 1G 4 → 3H 5 emission. • Green emission of Pr3+ ions also found to be increased due to energy transfer from ZnO. [ABSTRACT FROM AUTHOR]

Glasses of the composition(20–x) LiF–10 Sb 2 O 3 –10 B 2 O 3 –60P 2 O 5 : x NiO(0 < x < 0.25) were synthesized by conventional rapid melt quenching method. The non–crystalline nature of the samples was confirmed by XRD analysis and the glass forming abilities were analyzed by DTA studies. The compositional dependence of structural aspects of the glasses was analyzed by FT–IR and Raman studies. The DTA, FT–IR and Raman studies suggested an increasing degree of disorder in the glass network with increasing concentration of NiO up to 0.20 mol %. The reversal trend observed beyond 0.20 mol% is attributed to an increasing polymerization of glass network. The optical absorption (OA) and photoluminescence (PL) studies were also carried on these glasses. The results of OA and PL spectral studies suggested that the gradual increase of octahedral Ni 2+ ions with the increase in the concentration of NiO up to 0.20 mol%. Electrical properties viz., dielectric dispersion, DC and AC conductivity of the titled glass samples were also performed on titled glass samples. The observed increase in the values of dielectric constant, dielectric loss and AC conductivity (at any frequency and temperature) with the increase in the concentration of NiO up to 0.20 mol%is ascribed to the increasing space charge polarization in the glass network. The results of conductivity studies indicated that there is a mixed conduction (both ionic and polaronic) and the polaron hopping seems to prevail over ionic conduction in the glasses containing less than 0.20 mol% of NiO. [ABSTRACT FROM AUTHOR]

Emission characteristics of Pr 3+ ions sensitized with different concentrations Mn 2+ ions in BaO–Al 2 O 3 – B 2 O 3 –SiO 2 (BaAlBS) glass host were investigated. To have some pre-understanding over the structural modifications taking place in the glass network (which may help in understanding the variations the PL emission) due to the variation in the concentration of MnO, the spectroscopic studies like IR, EPR were also undertaken. The analysis of the results of IR spectral studies have indicated a gradual increase in the degree of depolymerisation of the glass network with increase in the concentration of MnO, whereas the EPR spectral studies have revealed a gradual increase in the concentration of octahedral positions of Mn 2+ ions in the glass network. The luminescence emission spectrum of Pr 3+ ions (individually) doped glass when excited at 476 nm exhibited conventional emission bands due to 3 P 0 → 3 H 4 , 3 H 5 , 3 H 6 ; 3 P 1 → 3 H 5 , 3 F 3 and 1 D 2 → 3 H 4 transitions in the visible region. The emission spectrum of Mn 2+ ions (individually) doped glasses when excited at the same wavelength also exhibited a distinct emission band at about 600 nm identified as being due to 4 T 1g → 6 A 1g octahedral transition s of Mn 2+ ions. When the Pr 3+ ions are codoped with Mn 2+ ions, a substantial hike in the orange emission band of Pr 3+ ions could be visualized. When the glasses are co-doped with 1.0 mol% of MnO, nearly 4 fold increase in the intensity of 3 P 0 → 3 H 6 (orange emission band) is observed. The increase is attributed to the transfer of energy from 4 T 1g → 6 A 1g emission transition of Mn2+ ions to 3 P 0 → 3 H 6 emission transition of Pr 3+ ions. The results were further quantitatively analyzed using IR and EPR spectral studies and finally concluded that Mn 2+ ions are efficient sensitizers in improving the orange red emission of Pr 3+ ions in the titled glass host. [ABSTRACT FROM AUTHOR]

40Li 2 O-4MO-55B 2 O 3 : 1Nd 2 O 3 , where MO Nb 2 O 5 , MoO 3 and WO 3 glasses were prepared by conventional melt quenching technique; the photoluminescence spectra (excited at 800 nm) of these glasses were recorded at room temperature. These glasses exhibited the emission bands ascribed to 4 F 3/2 → 4 I 9/2, 11/2, 13/2 transitions. The radiative transition probability (A T ) of emission transitions was characterized as a function of linear combination of Judd-Ofelt (J-O) parameters (Ωλ , λ = 2, 4 and 6) which are used to derive radiative properties of the fluorescent levels. Branching ratio (β R ) was enlightened in terms of the spectroscopic ratio (Ω 4⁄ Ω 6 )⋅ Interpretation of the data shows that these glasses have the favorable local structure for Nd 3+ ions to emit laser transition 4 F 3/2 → 4 I 11/2 (∼1060 nm) as Ω 6 > Ω 4 . Spontaneous emission probability (A), the radiative life time (τ R ) and stimulated emission cross-section (σ E ) of the present glasses were determined. [ABSTRACT FROM AUTHOR]

The objective of this study is to investigate the principal role of Y 2 O 3 , Sc 2 O 3 and HfO 2 on the enhancement of 1.06 μm emission beam of Nd 3+ ion in PbO–Sb 2 O 3 glass system. The emission spectrum of Nd 3+ doped glass exhibited emission bands at 900, 1060 and 1335 nm. When the glasses are co-doped with Y 2 O 3 , Sc 2 O 3 and HfO 2 and excited at 528 nm, a substantial hike in the intensity of 1060 nm emission band is observed. The comparison of luminescence efficiency of Nd 3+ ion of the glasses mixed with three co-dopants indicated the highest enhancement in the intensity of this emission in the glass co-doped HfO 2 . The reasons for such enhancement have been discussed in the light of varying environment of the glass network in the vicinity of Nd 3+ rare earth ions. [ABSTRACT FROM AUTHOR]

Glasses of composition PbO–Nb 2 O 5 –GeO 2 –SiO 2 doped with different concentrations of Cr 2 O 3 (ranging from 0 to 0.5 mol%) were prepared by conventional melt quenching technique. The prepared glasses were characterized by X-ray diffraction (XRD). Spectroscopic studies viz., optical absorption, EPR, FTIR, Raman and photoluminescence were carried out on these glasses. The optical absorption spectra exhibited three bands at about 646, 674 and 711 nm which are the characteristic bands of octahedral Cr 3+ ions. From the analysis of the absorption spectra the crystal field splitting parameters D q , B and nephelauxetic parameters (β and h ) were evaluated. The EPR spectra exhibited two resonance signals at g≈1.97 and g≈4.84. FTIR and Raman spectra have revealed the increasing presence of GeO 6 and NbO 6 structural units in the glass network with increasing the concentration of Cr 2 O 3 in the glass network. Photoluminescence spectra exhibited a broad emission band in the wavelength region 600 to 850 nm with a meta center at about 680 nm which is also a characteristic of Cr 3+ ions. Correlating optical and EPR data the molecular bonding coefficient parameter (α) has been evaluated. The quantitave correlation and analysis of all the results indicated that the glasses doped with higher content of Cr 2 O 3 are efficient luminescence materials. [ABSTRACT FROM AUTHOR]

Gd 3+ doped barium borophosphate glasses mixed with varying concentration of Al 2 O 3 are synthesized. Photoluminescence, thermoluminescence and other spectroscopic studies viz., IR and EPR spectral studies, have been carried out. IR spectral studies of these glasses indicated that there is a gradual increase in the degree of depolymerization of the glass network with increase in the concentration of Al 2 O 3 upto 3.0 mol%. The EPR spectral studies revealed the lowest concentration of Gd 3+ ion clusters in the glass mixed with 3.0 mol% of Al 2 O 3 . The photoluminescence emission spectra exhibited strong ultraviolet blue emission at 311 under excitation at 273 nm due to 6 P 7/2 → 8 S 7/2 transition of Gd 3+ ions. The intensity of this band is found to be enhanced four times when the glass mixed with 3.0 mol% of Al 2 O 3 with respect to that of alumina free glass. The enrichment of this emission is attributed to the declustering of Gd 3+ ions by Al 3+ ions. Thermoluminescence (TL) characteristics of these glasses have also been investigated after irradiating them with different doses of γ-rays (in the range 0–8.0 kGy). The TL emission exhibited a dosimetric peak at about 200 °C. The TL output under this glow peak is observed to increase with increase of γ-ray dose. For any fixed γ-ray dose, the TL output is increased with increasing Al 2 O 3 content up to 3.0 mol% and beyond this concentration quenching of TL is observed. The mechanisms responsible for TL emission and the variation in TL output with the concentration of Al 2 O 3 are quantitatively discussed in terms of electron and hole centers developed due to interaction of γ-rays with the glass network. The dose response of these glass samples exhibited linear behavior in the dose range 0–8.0 kGy. [ABSTRACT FROM AUTHOR]

• Sb 2 O 3 ‒Li 2 O‒MO (M=Mg, Ca & Sr): Eu 2 O 3 glasses were prepared. • Optical absorption and PL spectra were recorded. • R/O intensity ratio is the highest for SrO mixed glasses. • Reasons for enhancement are enlightened on the basis of structural variations. In this study, role of three modifier oxides (viz., MgO, CaO and SrO) on red luminescence efficiency of Eu3+ ions in Sb 2 O 3 ‒Li 2 O glass system was investigated. The absorption spectra of these glasses exhibited the bands due to 7F 0 → 5D 4 , 3 , 2 , 1 , 0 ,5G 4 , 2 , 5L 6 and 7F 0 , 1 →7F 6 transitions in the visible and NIR regions, respectively. Emission spectra recorded at λ exc =394 nm exhibited the bands due to 5D 0 →7F J (J = 0 to 4) transitions. Out of these, the band due to5D 0 →7F 2 (red emission) was found to be more intense. J-O parameters, Ω 2 and Ω 4 were evaluated using integral R/O ratio of emission spectra. Radiative parameters viz., A R , β R and σE P for Eu3+ions were calculated using J-O parameters, These parameters were observed to be the maximal for SrO mixed glasses. Variations of local symmetry and covalency in the vicinity of Eu3+ ions were found to be responsible for such larger values of these parameters and for intense red emission for SrO mixed glasses. [ABSTRACT FROM AUTHOR]

• Li2O-HfO2-SiO2 glasses with fixed Sm2O3 and varied content of Au2O3 were prepared. • OA spectra exhibited a broad band in the visible region due to SPR of Au0 particles. • PL spectra of the glasses containing Au0 MPs showed a wide (sp → d) emission band. • PL spectra of Sm3+ doped glasses revealed bright orange and red emission bands. • Role of Au0 particles on improving red emission efficiency of Sm3+ ions was discussed. In this study, Li 2 O-HfO 2 -SiO 2 -Sm 2 O 3 -Au 2 O 3 glasses (doped with fixed concentration of Sm 2 O 3 and varied contents of Au 2 O 3) were synthesized and characterized. The role of Au0 particles on improvisation of red emission of Sm3+ ions was investigated. Optical absorption (OA) spectra of these glasses indicated a number of bands excited from 6H 5/2 of Sm3+ ions. A broad band in the greenish-yellow spectral region due to surface plasmon resonance (SPR) of Au0 nanoparticles was also detected in these spectra. Photoluminescence (PL) spectra of (Sm free glasses) embedded with Au0 metallic particles (MPs) showed a wide band in the visible region ascribed to the transition of electrons from sp → d energy bands. Luminescence spectra of Sm3+ doped glasses revealed bright orange and red emission bands with substantial increased intensities with increased concentration of Au 2 O 3. Effect of Au0 MPs on the red emission efficiency of Sm3+ ions was emphasized with kinetic rate equations. [ABSTRACT FROM AUTHOR]

This investigation is mainly devoted to the studies on enrichment of green emission of Ho 3+ ions in PbO SiO 2 glasses containing 1.0 mol% of Ho 2 O 3 by co-doping with different concentrations of Bi 2 O 3 (0–9.0 mol%). The optical absorption spectra, photoluminescence spectra, photoluminescence decay, IR and Raman spectral studies on the above mentioned glasses have been performed as a function of Bi 2 O 3 concentration. The emission spectra of Bi 2 O 3 free glasses exhibited green and red emissions due to 5 S 2 + 5 F 4 → 5 I 8 and 5 F 5 → 5 I 8 transitions of Ho 3+ ions, respectively, when excited at 450 nm. The spectra also exhibited NIR emission due to the 5 I 7 → 5 I 8 transition at 2.0 μm. The intensity of green emission is found to be significantly enhanced (nearly three times) when the glasses are mixed with 5.0 mol% of Bi 2 O 3 . The reason for this enhancement has been identified as being due to the energy transfer from Bi 3+ to Ho 3+ ions. The predominant participation of Bi 3+ ions in modifying positions and due to the de-clustering of Ho 3+ ions are found to be the other reasons. The overall enhancement of emission has further been explained with the help of rate equations. The quenching of luminescence emission observed in the glasses containing more than 5.0 mol% of Bi 2 O 3 is attributed to the reason that in these glasses the Bi 3+ ions largely participate in the network forming positions and increase the phonon losses. These arguments have been quantitatively explained with the help of IR and Raman spectral studies. [ABSTRACT FROM AUTHOR]

CuO doped sodium silicate glasses mixed with different concentrations of Bi 2 O 3 are synthesized. Photoluminescence, thermoluminescence characteristics have been investigated. Photoluminescence emission spectra exhibited a broad band in the bluish green region under excitation at 325 nm. This band is attributed to 3 D 1 → 1 S 0 transition of (Cu + ) 2 pairs. The intensity of this emission band is observed to increase with the concentration of Bi 2 O 3 up to 20 mol%. The increase is attributed to the increase in the concentration of Cu + ions. Thermoluminescence (TL) emission exhibited a dosimetric peak at about 250 °C. The TL output under this glow peak is observed to decrease with increase of γ–ray dose and also with the increase of Bi 2 O 3 content. The mechanisms responsible for TL emission and the variation in TL output with the concentration of Bi 2 O 3 are quantitatively discussed in terms of electron and hole centers developed due to interaction of γ–rays with the glass network. [ABSTRACT FROM AUTHOR]

Lead silicate glasses mixed with 5.0 mol% of Bi 2 O 3 and doped with varying concentrations of CoO have been synthesized. Optical absorption, infrared and photoluminescence spectra and luminescence decay profiles of the prepared glasses were recorded at ambient temperature. Analysis of IR spectral results have indicated that there is increasing proportion of the tetrahedral Co 2+ ions in the glass network with increase in the concentration of CoO. The emission spectra of Bi 2 O 3 free glasses exhibited two significant bands in the orange and red regions when excited at 595 nm. These bands are identified as being due to 4 T 1 ( 4 P)→ 4 A 2 ( 4 F) and 4 T 1 ( 4 P) → 4 T 2 ( 4 F) tetrahedral transitions of Co 2+ ion, respectively. The intensity of orange emission band due to 4 T 1 ( 4 P)→ 4 A 2 ( 4 F) transition is found to be enhanced nearly five times when the glasses are mixed with 5.0 mol% of Bi 2 O 3 . The quantitative analysis of these results indicated that the energy transfer from 3 P 1 → 1 S 0 emission transition of Bi 3+ ions to 4 T 1 ( 4 P)→ 4 A 2 ( 4 F) tetrahedral transition of Co 2+ ion is responsible for the enrichment of this orange emission. [ABSTRACT FROM AUTHOR]

Highlights: [•] PbO–Al2O3–SiO2:Ho2O3 glasses with varying concentration of Al2O3 were synthesized. [•] Optical absorption, luminescence spectra and decay profiles were recorded. [•] The intensity of all Ho3+ emission bands increased with increasing Al2O3 content. [•] Increase is attributed to declustering of Ho3+ ions by Al3+ ions and self up-conversion. [ABSTRACT FROM AUTHOR]

Abstract: Pr3+ doped lead alumino silicate glasses with varying concentrations of Al2O3 (from 5 to 10mol%) have been synthesized. The IR and Raman spectral studies of these glasses have indicated that there is a gradual increase in the depolymerization of the glass network with an increase in the concentration of Al2O3. The optical absorption, luminescence spectra and fluorescence decay curves of these glasses were recorded at room temperature. The luminescence spectra of these glasses have exhibited the bands due to 3P0 → 3F2, 3F3, 3H6, 3H4, 3H5 transitions. From these spectra, the radiative parameters viz., spontaneous emission probability A, the total emission probability AT, the radiative lifetime τ, the fluorescent branching ratio β of different transitions that originated from the 3P0 level of Pr3+ ions have been evaluated. A considerable enhancement in the luminescence emission, especially in the red region corresponding to 3P0 → 3H6, 3F2 transitions has been observed. The increase has been attributed to the possible admixing of wavefunctions of opposite parities and due to the declusterization of Pr3+ ions by Al3+ ions in the glass network. The branching ratio β has been observed to be the highest for the transition 3P0 → 3F2 and it is found to be ~50% for the glass mixed with 10mol% of Al2O3. The CIE color coordinates for three glasses have been evaluated and found to be in the bright red region. [Copyright &y& Elsevier]

Abstract: Optical absorption and photoluminescence spectra (PL) of the glasses possessing compositions (49− x) Li2O−x Y2O3−50 SiO2:1.0 Ce2O3/1.0Yb2O3 and (49− x) Li2O−x Y2O3−50 SiO2:(0.5 Ce2O3 +0.5 Yb2O3) with x varying from 5 to 15mol% were studied. The PL spectra of Ce3+ doped glasses excited at 360nm exhibited two broad parity allowed 5d(2D)→4f(2F5/2,7/2) bands in the blue spectral region, whereas the spectra of Yb3+ doped glasses excited at 900nm exhibited a broad emission band centered at about 980nm due to 2F5/2 → 2F7/2 transition. A significant enhancement in the intensity of NIR emission is observed due to the sensitization with Ce3+ ions. The increase in the rate of energy transfer from Ce3+ to Yb3+ could be observed with increasing Y2O3 content. The reasons for such improvement have been discussed within a framework of structural modifications taking place in the vicinity of Yb3+ ions. [Copyright &y& Elsevier]

Abstract: Optical absorption and photoluminescence characteristics of Sm3+ ions in lead silicate glasses mixed with different concentrations of Al2O3 (5–10mol%) have been investigated. From these studies, the radiative properties viz., spontaneous emission probability A, the total emission probability, the radiative lifetime τ R, the fluorescent branching ratio β of emission transition of 4G5/2 → 6H7/2 along with other transitions for Sm3+ have been evaluated and found to be the highest for the glass mixed with 8.0mol% of Al2O3.The IR spectral studies have indicated that Al3+ ions do participate in the glass network with AlO4 and AlO6 structural units and further revealed that the concentration of octahedral aluminium ions induce bonding defects in the glass network. Such bonding defects are assumed to be responsible for low phonon losses in these glasses and lead to higher values of radiative parameters for the glass mixed with 8.0mol% of Al2O3. [Copyright &y& Elsevier]

Abstract: Li2O–ZrO2–SiO2: Nd3+ glasses mixed with Nb2O5, Ta2O5 and La2O3 were prepared. Optical absorption and photoluminescence spectra of these glasses have been recorded at room temperature. The Judd–Ofelt theory was successfully applied to characterize Nd3+ spectra of all the three glasses. From this theory, various radiative properties like transition probability A, branching ratio β r, the radiative lifetime τ r, for 4F3/2 emission level in the spectra of these glasses has been evaluated. The radiative life time for 4F3/2 level of Nd3+ ions has also been measured and quantum efficiencies were estimated. Among the three glasses studied, the La2O3 mixed glass has exhibited the highest quantum efficiency. The reasons for such higher value have been discussed based on the relationship between the structural modifications taking place around the Nd3+ ions. [Copyright &y& Elsevier]

Abstract: We have synthesized Li2O–Nb2O5–ZrO2–SiO2 glasses and subsequently crystallized them with different CuO contents (0–0.3mol% in the steps of 0.05) as nucleating agents and characterized them by XRD, SEM and DSC. We have also studied IR, Raman, ESR, optical absorption photoluminescence and dielectric properties to explore the influence of copper valance states and their coordination with oxygen on structural and optoelectronic aspects of the samples. These studies have indicated that there is a possibility for the copper ions to exist in Cu+ and Cu3+ states (in addition to Cu2+ state) in these glass ceramics and participate in the glass network forming. Finally, we have undertaken photoinduced second harmonic generation studies (after the samples were dc field treated at elevated temperatures) with 10ns Er:glass laser (of wavelength 1540nm with power densities up to 1.5GW/cm2) to examine the suitability of these materials for optically operated devices. The analysis of the results of non-linear optical studies has shown that 0.2mol% of CuO is the optimal concentration for getting the highest values of second order susceptibility coefficients. [Copyright &y& Elsevier]

Abstract: In this study, the principal role of Al2O3 on the features of the photoluminescence spectra of Tm3+ ion and upconversion phenomenon in Tm3+ and Er3+ codoped CaF2−Al2O3−P2O5−SiO2 glass system has been investigated. The concentration of Al2O3 is varied from 2 to 10mol% while that of Er3+ and Tm3+ is fixed. IR and Raman spectral studies have indicated that there is a gradual increase in the degree of disorder in the glass network with increase in the concentration of Al2O3 up to 6.0mol%. This is attributed to the presence of Al3+ ions in octahedral positions in larger proportions. When the glasses are doped with Tm3+ ions, the blue and red emissions were observed, whereas in Er3+ doped glasses blue, green and red emissions were observed. When the glasses are codoped with Tm3+ and Er3+ ions and excited at 790nm, all the three emission lines were observed to be reinforced, especially in the glasses mixed with 6.0mol% of Al2O3. The IR emission band detected at about 1.8μm due to 3F4→3H6 transition of Tm3+ ions is also observed to be strengthened due to codoping. The reasons for enhancement in the intensity of various emission bands due to codoping have been identified and discussed with the help of rate equations for various emission transitions. [Copyright &y& Elsevier]

Abstract: Li2O–Nb2O5–ZrO2–SiO2 glasses mixed with different concentrations of V2O5 were crystallized. The samples were characterized by XRD, SEM and DTA techniques. The SEM pictures indicated that the samples contain well defined and randomly distributed crystal grains. The X-ray diffraction studies have revealed the presence of several crystalline phases in these samples. Optical absorption, ESR and photoluminescence spectral studies on these samples have indicated that a considerable proportion of vanadium ions do exist in V4+ state in addition to V5+ state and the redox ratio seems to be increasing with increase in the concentration of crystallizing agent V2O5. The infrared spectral studies have pointed out the existence of conventional SiO4, ZrO4, NbO6, VO structural units in the glass ceramic network. The study of dielectric properties suggested a decrease in the insulating character of the glass ceramics with increase in the crystallizing agent. A.C. conductivity in the high temperature region seems to be connected mainly with the polarons involved in the process of transfer from V4+↔V5+ ions. [ABSTRACT FROM AUTHOR]

Abstract: Na2SO4–P2O5:Sm3+ glasses mixed with three different alkaline earth modifier oxides viz., MgO, CaO and BaO were prepared. Optical absorption and photoluminescence spectra of these glasses have been recorded at room temperature; the Judd–Ofelt theory was successfully applied to characterize these spectra. From this theory, various radiative properties like transition probability A, branching ratio β r, the radiative lifetime τ r, for various emission levels in the spectra of these glasses have been determined and reported. An attempt has also been made to throw some light on the relationship between the structural modifications and luminescence efficiencies in the change of scenario for modifying oxides in the glass network. [ABSTRACT FROM AUTHOR]

Abstract: PbO–As2O3 glasses mixed with different concentrations of CoO (ranging from 0 to 1.0 mol%) were crystallized. The samples were characterized by X-ray diffraction, scanning electron microscopy, EDS and differential scanning calorimetric techniques. The X-ray diffraction studies have indicated the presence of Pb(As2O6), Pb3(AsO4)2, Co6As2O11, Co3O4 crystalline phases in these samples. Optical absorption, IR and photoluminescence studies of these samples have been carried out. The analysis of the results of these studies has indicated that the cobalt ions exist in Co2+ and Co3+ states in the glass matrix. The studies have further revealed that as the concentration of the CoO is increased, there is a gradual transformation of cobalt ions from tetrahedral to octahedral positions. [Copyright &y& Elsevier]

Abstract: ZnF2–As2O3–TeO2 glasses mixed with different concentrations of V2O5 (ranging from 0 to 0.6mol%) were synthesized. The amorphous nature of these glasses was checked by X-ray diffraction and scanning electron microscopy techniques. A variety of properties, i.e. optical absorption, photoluminescence, infrared, ESR spectra and dielectric properties (constant ε′, loss tan δ, ac conductivity σ ac over a wide range of frequency and temperature) of these glasses have been explored. The optical absorption, electron spin resonance studies together indicated vanadium ions coexist in V4+ with V5+state in these samples. The IR spectra of these samples have exhibited bands due to ν s-TeO2ax and AsO3 structural groups; these results indicated the most structural disorder in the network as the concentration of V2O5 is increased. Luminescent emission spectra recorded at room temperature of these glasses excited at 640nm have exhibited a broad emission band in the spectral wavelength range of 750–850nm. The luminescence efficiency is found to be the highest for the sample doped with 0.6mol%. The dielectric parameters viz., ε′, tan δ and σ a.c are found to increase and the activation energy for ac conduction is found to decrease with the increase in the concentration of V2O5 up to 0.6mol%, reflecting an increase in the concentration of V4+ ions that take part modifying positions in the glass network. The ac conduction in these glasses could satisfactorily be explained by both classical activation energy and the tunneling phenomena. [Copyright &y& Elsevier]

Abstract: PbO–CaF2–P2O5 glasses containing small concentrations of CuO from 0 to 0.6mol% were prepared. A number of studies viz., dielectric studies (constant ɛ′, loss tan δ, ac conductivity σ ac over a range of frequency and temperature), infrared, optical absorption ESR and photoluminescence spectra of these glasses, have been carried out. The variations observed in all these properties with the concentration of copper ions have been analyzed in the light of different oxidation states and environment of copper ions in the glass network. [Copyright &y& Elsevier]

Abstract: Li2O–MO (Nb2O5, MoO3 and WO3)–B2O3 glasses doped with four rare earth ions, viz., Pr3+, Nd3+, Sm3+ and Er3+ (of 1.0mol% each) were prepared. The glasses were characterized by X-ray diffraction, differential scanning calorimetry, ESR, optical absorption and photoluminescence spectra. From the measured intensities of various absorption bands of these glasses, the Judd–Ofelt parameters Ω 2, Ω 4 and Ω 6 have been evaluated. The Judd–Ofelt theory could successfully be applied to characterize the absorption and luminescence spectra of these glasses. From this theory, various radiative properties like transition probability A, branching ratio β r, the radiative life time τ r and the emission cross-section σ E for various emission levels of these glasses have been determined and reported. An attempt has also been made to throw some light on the relationship between the structural modifications and luminescence efficiencies of all the three glasses. The analysis of the data indicated high non-radiative losses in Nb2O5 mixed glasses. [Copyright &y& Elsevier]

Abstract: BaO–P2O5 glasses mixed with the three metal oxides viz., Al2O3, Ga2O3 and In2O3 doped with Tb2O3 were prepared. The glasses were characterized by X-ray diffraction and differential thermal analysis. Optical absorption and photoluminescence spectra and thermoluminescence (TL) of these glasses have been studied. From the measured intensities of various absorption bands of these glasses, the Judd–Ofelt parameters Ω 2, Ω 4 and Ω 6 have been evaluated and compared with those of other reported glass systems. The Judd–Ofelt theory could successfully be applied to characterize the absorption and luminescence spectra of these glasses. From this theory various radiative properties like transition probability A, branching ratio β r, the radiative lifetime τ r and the emission cross-section σ E for various emission levels of these glasses have been determined and reported. An attempt has also been made to throw some light on the relationship between the structural modifications and luminescence efficiencies of all the three glasses. The analysis of TL data indicate high non-radiative losses in In2O3 mixed glasses. [Copyright &y& Elsevier]