Bismuth Phosphate Glasses Research Articles

Investigation of emission characteristics in Er3+- doped bismuth phosphate glasses for NIR laser materials

Bismuth flourophosphate glasses doped with Er3+ ions (0.5 mol %) were synthesized using different modifier fluorides with the aid of melt quenching route. The glass samples were labelled as PBiBaAFT (where AF = Li, Na, Mg, K, Ca and Sr fluorides). The influence of cations of network modifiers on the structure and thereby spectroscopic properties of Er3+ ions was analysed via Powder XRD, FTIR, optical absorption and photoluminescence. Existence of relevant vibrational groups and modifications in structure due to the different admixture modifier cations were recognized via FTIR spectra. The Judd-Ofelt parameters abide by the trend Ω2 > Ω6 > Ω4 in the PBiBaLiT, PBiBaKT, PBiBaCaTand PBiBaSrT glasses whereas the trend was noticed to be Ω2 > Ω4 > Ω6 for PBBiNaT and PBiBaMgT glasses respectively. The visible emission spectra were recorded by exciting at 379 nm exhibit three emission bands centered at 526 nm, 544 nm and 686 nm. NIR emission spectra were recorded by exciting at 980 nm exhibit broad emission at 1535 nm. Admixture of different cations could exhibit change in luminescence intensity and radiative parameters of the prepared glasses. Spectroscopic parameters such as radiative transition probability (A), branching ratio (β), absorption cross section (∑), effective bandwidth (Δλeff) and optical band gain (σe × Δλeff) are calculated. The mid infrared spectroscopic features were investigated.

Assessment of radiation shielding performance of Li2O-BaO-Bi2O3-P2O5 glass systems within the energy range from 0.081 MeV to 1.332 MeV via MCNP6 code

The purpose of this study is to assess the radiation shielding performance of the lithium barium bismuth phosphate glass system from energy 0.081–1.332 MeV where the concentration (mol%) of barium and bismuth were varied yet lithium and phosphate were fixed. A few radiation shielding parameters such as linear attenuation coefficient (LAC), mass attenuation coefficient (MAC), half value layer (HVL), and effective atomic number (Zeff) of the glass system were calculated through MCNP6 code. Enhancement of the amount of Bi2O3 on the lithium barium bismuth phosphate glass system amended the density of glass systems that’s why the value of effective atomic number was increased. Obtained results represent that the value of half value layer was 27 times higher for upsurging the incident photon energy from 0.081 M to 1.332 MeV. Moreover, at energy 1.332 MeV, the value of half value layer for sample LiBaBiP5 and LiBaBiP30 were 3.80 cm and 2.73 cm, respectively, which specifies that with the greater amount of Bi2O3 in the lithium barium bismuth phosphate glass system enhanced the radiation shielding ability. Glass system 5Li2O-5BaO-30Bi2O3-60 P2O5 showed the highest value of radiation shielding performance from energy 0.081–1.332 MeV. Eventually, it can be stated that Bi2O3 is the more suitable additives to enhance the shielding ability of glass material among the two oxides BaO, and Bi2O3.

Investigation of structural and optical properties of Pr3+ doped and Pr3+/Dy3+ co-doped multicomponent bismuth phosphate glasses for visible light applications

Pr3+ doped 59.5P2O5+15Bi2O3+10BaF2+10xF+05TeO2+0.5Pr6O11 glasses and Pr3+/Dy3+ co-doped 59P2O5+15Bi2O3+ 10BaF2+ 10xF + 05TeO2+0.5Dy2O3+0.5Pr6O11 glasses (where xF = LiF, NaF, MgF2, KF, CaF2 and SrF2) were synthesized using melt quenching route. Structural properties were researched for different modifier fluorides. With the dopant constant concentration the absorption and luminescence intensity variance influenced by this multicomponent incorporation has been observed. The energy transfer between resonance levels of Pr3+ and Dy3+ through fluorescence studies also examined for Mg and Sr glasses. Long-range nature of prepared glasses, morphological studies with elemental probe, various functional groups pertaining to glass matrices and the non-bridging oxygen bonds with PO4 tetrahedron or depolymarization of oxygen bonds in the presence of the modifier cations with phosphates were thoroughly understood with PXRD, FTIR and 31P NMR characterizations. Judd-Ofelt (J-O) theory has been adopted to estimate important optical parameters. From the fluorescence studies laser characteristic parameters such as optical band gains (σe × τR) and gain bandwidths (σe × Δλeff) were calculated and compared in the present fabricated glasses influenced by various modifiers.

Probing into structural and spectroscopic properties of Dy3+ doped and Eu3+/Dy3+ co-doped bismuth phosphate (BiPO4) glass ceramics with different modifier fluorides

In the present work, the synthesis of BiPO4 phase resided in transparent bismuth phosphate glass ceramics has been accomplished by regular melt quenching route. Impact of modifier fluorides on structural and spectroscopic properties of Dy3+ doped and Eu3+/Dy3+ co doped different bismuth phosphate glass ceramics via PXRD, FTIR, XPS, SEM, optical absorption, emission, excitation and decay measurements has been thoroughly examined. Various spectroscopic parameters were calculated from the absorption spectra using Judd-Ofelt (J-O) theory and analyzed the parameters. From the emission spectra, emission characteristics were studied via optical band gains (σe × τR), gain bandwidths (σe × Δλeff), Y/B ratios and lifetimes (τ) from decay curves. The effect of Eu3+/Dy3+ co-doping on emission properties has been studied in these glass ceramics where energy transfer was observed. Color coordinates for all the studied systems also inferred. Among various multi component glass ceramics studied in the present work, NaF2 system could be suitable for laser and white light applications.

White Emission from Li2O-BaO-Bi2O3-P2O5 Glass Doped with Dy3+ for Optical Condensed Material Applications

Dy3+-doped lithium barium bismuth phosphate glasses were synthesized by the melt-quenching. The structural characteristics of the synthesized glasses were investigated by Fourier transform infrared (FTIR) spectroscopy. Symmetric and asymmetric vibrations of phosphorous oxygen groups were prominent bands in the FTIR spectra. Judd–Ofelt theory have been evaluated by the intensities of absorption bands in order to calculate oscillator strength (f). Luminescence intensity increases with increase in BaO content due to substitution of Ba2+ replacing Bi3+ which lead more void spaces providing enough space for Dy3+ ions to fit in. The branching ratio β parameter was distinguished to be maximum for the emission transition of 4F9/2 → 6H13/2 with the values of 0.59. LBBPDy glasses reveal an ideal warm white region when observed in CIE diagram. Our investigation reveals that the synthesized glasses may be utilized as a solid-state lighting material in various technological and industrial applications.

Influence of optimized concentration of Dy3+ ions on optical and luminescence properties of P2O5 + Bi2O3 + Na2CO3 + SrF2 glasses for solid state visible laser and w-LED applications

The fluoride-based bismuth phosphate (PBNS) glasses are doped with Dysprosium ions are fabricated by using the method conventional melt quenching. For synthesized PBNS glasses physical parameters were evaluating, moreover, the structural, optical, and fluorescence properties were analyzed/studied by XRD, FTIR, EDAX, photoluminescence study analysis, and optical absorption. The optical band gap is estimated based on the tauc's curve extracted from the absorption spectrum, and the value obtained shows a non-linear behavior with the concentration of doping ions. The intensity parameters (Ω 2 , Ω 4, Ω 6 .) were evaluated using Judd – Ofelt theory and which follows Ω 2 > Ω 4 > Ω 6 trend. From the emission spectra, the PBNSDy glasses doped with 1.0 mol% Dysprosium ions (PBNSDy10) attains the higher emission peak intensity among the prepared glasses. The 6 H 15/2 → 6 F 11/2 transition emitting the radiation at 473 nm was more intense than the other transition and attains a higher value for optical gain bandwidth (28.66 × 10 −25 cm 2 S), Stimulated emission cross-section (5.45 × 10 −21 cm 2 ) and branching ratio (0.63). The emission spectra are used to evaluate by colorimetric analysis of the 1931 CIE color coordinates, Y/B intensity ratio, and CCT values to see the adaptability of the fluorophosphate glass to solid-state white light LED applications. • Dy 3+ ions doped bismuth-based fluorophosphate glasses were prepared. • JO spectral intensity parameters were evaluated. • The 6 H 15/2 → 6 F 11/2 transition has higher σ emi (5.45 × 10 −21 cm 2 ) and β (0.63) values • CIE color coordinates were evaluated. • PBNSDy10 glass could be used for design of visible lasers/w-LEDs.

Influence of alkali and alkaline earths on structural and luminescence properties of Sm3+ doped lithium fluoro phosphate glass and different (Na, Mg, K, Ca and Sr) glass ceramics

Transparent glass ceramics comprising of BiPO4 nanocrystals in bismuth phosphate glass ceramics (59.5P2O5+15Bi2O3+10BaF2+10AF+05TeO2+0.5Sm2O3 where AF= alkali and alkaline earth fluorides) doped with Sm3+ ions were synthesized by typical melt quenching route. On the basis of data obtained from differential thermal analysis (DTA), prepared samples were analyzed for their thermal stability. Further powder X-Ray diffraction (PXRD) analysis has been done for all the samples to confirm the crystalline phase of BiPO4 and short-range order i.e., isotropic. Validations of various structural units were done with the help of FTIR. Spectral intensities were obtained using Judd-Ofelt (JO) theory for various absorption bands of Sm3+ ions using least square fit method for all the studied glass and glass ceramics. Various optical parameters of Sm3+ doped lithium phosphate glass and various glass ceramics were obtained from emission and absorption spectra studied in the present work. Theses optical parameters include JO intensity parameters (Ω2, Ω4 andΩ6), radiative transition probabilites (Aed), branching ratios (β), emission cross sections (σe), absorption cross sections (∑),gain bandwidths and optical gains (σe × Δλeff and σe × τR respectively). Influence of alkali and alkaline earths metals on radiation properties of various excited levels of Sm3+ has been investigated. In relation to the other glass networks and ceramics, SrF2 glass ceramics studied in the present work exhibited productive properties and could be useful in development of optical devices for visible laser applications.

Synthesis and structural analysis of trivalent europium (Eu3+) ions doped oxyfluoride (ZnBiNaPSr) glasses as prominent host materials for optical devices

A series of trivalent europium (Eu3+) ions doped zinc sodium strontium activated bismuth phosphate (P2O5-Bi2O3-Na2CO3-SrCO3-ZnF2-Eu2O3) glasses of different dopant ion compositions have been prepared by conventional melt quenching technique. Physical and optical parameters of the prepared glasses such as density (ρ), molecular weight (Mi), molar volume (VM), rare-earth ion concentration (NRE), polaron radius (rp), inter nuclear distance (ri) field strength (F), oxygen to phosphorus (O/P) ratio, refractive index (n), dielectric constant (ϵ), reflection losses (R), molar refractivity (RM), electron polarizability (αM), susceptibility (χ) oxygen packing density (OPD), metallization (M) and reflection factor (P) have been evaluated using the standard formulae. The amorphous/glassy nature was confirmed by the XRD pattern showing the broad hump cantered at 2θ=28° Surface morphological studies have been carried out using SEM analysis and EDS spectra reveal the successful incorporation of Eu3+ ions into the host matrix. Structural information was obtained from FT-IR spectra, recorded in 4000-400 cm−1 spectral region which consists of symmetrical, asymmetrical stretching and bending P=O, P-O-P, O-P-O and P-O-H vibrations along with OH- groups. Furthermore, all the prepared glasses were subjected to study for their optical and luminescence properties in detailed.

Role of bismuth content on structural and luminescence properties of Ho3+ doped phosphate glasses

0.5 mol% Ho3+ -doped bismuth phosphate (BiP) glasses with different (0, 5, 10 and 15 mol%) Bi content have been prepared by melt quenching method. Structural characteristics were investigated through XRD and 31P NMR spectroscopy. Optical characteristics were explored through optical absorption, photoluminescence and decay lifetime computations. Using Judd-Ofelt (J-O) theory, J-O intensity parameters Ωλ (λ = 2, 4, 6) have been calculated from the absorption spectra. Radiative properties such as radiative transition probabilities (AR), radiative lifetimes (τR) and fluorescence branching ratios (βR) for different excited states of Ho3+ ions have been examined. From luminescence spectra, stimulated emission cross-sections (σe) were evaluated for the observed two emission transitions in the green (5S2+5F4 → 5I8, 545 nm) and red (5F5 → 5I8, 658 nm) regions. Among all BiP glass matrices, Bi-5 has higher σe value (6.09 × 10−20 cm2) for the transition 5S2+5F4 → 5I8 of Ho3+ ion (green emission). Chromaticity coordinates were also calculated from the emission spectra which lie in the green region for all the bismuth contained glasses. Hence the Ho-doped BiP glasses studied in the present work are potential candidates for green emission lasers.

Luminescence behaviour and phonon sideband analysis of europium doped Bi2O3 based phosphate glasses for red emitting device applications

0.5 mol% of europium (Eu3+) doped bismuth phosphate glasses (BiP) with different contents (0, 5, 10 and 15 mol%) of bismuth and different (0.1, 0.3, 0.5, 1.0, 1.5 and 2.0) mol% of Eu3+ doped 5 mol% bismuth contained BiP glasses were made by melt-quenching technique. The structural and photoluminescence properties were analysed via FT-Raman, excitation, luminescence and decay time computations. Judd-Ofelt (J-O) parameters were evaluated from the emission spectra and also various radiative properties such as radiative transition probabilities (AR), radiative lifetimes (τrad), stimulated emission cross-sections (σe), branching ratios (β), optical gain bandwidths (σexΔλeff) and optical gain (σexτrad) values for the observed emission transitions are studied. The electron-phonon coupling constants (g), phonon energies (hω) and the multiphonon relaxation rates (WMPR) were determined. The decay curves of 5D0 level of Eu3+ in all the studied glasses exhibit single exponential nature. The lifetimes are obtained from the decay curves and reported. The CIE chromaticity co-ordinates were computed and they have fallen in red region. The characteristic red luminescence emission around 612 nm for 5D0→7F2 transition confirmed that the Eu3+ doped BiP glasses might be useful to fabricate red lasers and display devices.

Investigations on spectroscopic properties of Nd3+ doped alkali bismuth phosphate glasses for 1.053 μm laser applications

The neodymium doped alkali bismuth phosphate (ABiP:Nd3+) glasses with the chemical composition (65 − x)P2O5 + 15Bi2O3 + 10Li2O + 10Na2O + xNd2O3 (where x = 0.1, 0.3, 0.5, 1.0, 1.5, 2.0 in mol%) have been prepared by the conventional melt quenching technique and characterized through various spectroscopic measurements. The spectroscopic parameters have been determined from the absorption and emission measurements together with Judd-Ofelt analysis. Addition of bismuth oxide to the phosphate matrix significantly increases radiative parameters such as radiative transition probability, measured lifetime, quantum efficiency and stimulated emission cross-sections. Three emission lines at 874, 1053, 1323 nm have been registered for Nd3+ in alkali bismuth phosphate glasses, which corresponds to the transitions originating from 4F3/2 level to the 4I9/2, 4I11/2 and 4I13/2 levels of Nd3+ ion, respectively. The quite larger values for laser parameters like peak emission cross-sections, gain bandwidth, figure of merit, optical gains and saturation intensities have been obtained for 4F3/2 → 4I11/2 transition of Nd3+ ions in alkali bismuth phosphate glasses, which is promising for NIR laser application at 1.053 μm.

Energy transfer studies and neutral to warm white light generation in Dy3+-Sm3+ co-doped bismuth phosphate glasses for lighting applications

A series of bismuth phosphate (BiP) glasses activated with 0.5 mol% of Dy3+ and different concentrations (0.1, 0.3, 0.5, 1.0, 1.5 and 2.0 mol%) of Sm3+ ions were prepared by melt quenching technique. These are characterized through optical absorption, photoluminescence and decay measurements for spectroscopic investigations. The luminescence spectra have been studied under selected excitation wavelengths to examine the energy transfer mechanism in the present Dy3+-Sm3+ co-doped glass by varying Sm3+ ion concentration. The lifetimes of both 4F9/2 level of Dy3+ ion and 4G5/2 level of Sm3+ ion of co-doped glasses have obtained and found to be decreased with increase in Sm3+ ion concentration. The emission intensity increased with the increase of Sm3+ ion concentration (upto 1.5 mol%) which confirms the energy transfer process between Dy3+ to Sm3+ ions. The CIE chromaticity co-ordinates (x, y), correlated color temperature (CCT) and color purity (CP) were determined from the emission data. From the CIE, CCT and CP values, it can be concluded that there is a color hue from neutral to warm white light region due to Sm3+ ion concentration and selected excitation wavelength. Hence, the obtained results strongly suggest that the present Dy3+-Sm3+ co-doped bismuth phosphate glasses could be useful for lighting applications.

Structural and luminescence properties of Sm3+ -doped bismuth phosphate glass for orange-red photonic applications.

In the present study, the effect of bismuth oxide (Bi2 O3 ) content on the structural and optical properties of 0.5Sm3+ -doped phosphate glass and the effect of concentration on structural and optical properties of Sm3+ -doped bismuth phosphate (BiP) glass were studied. Structural characterization was accomplished using X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy and 31 P nuclear magnetic resonance (NMR) spectroscopy. Optical properties were studied using absorption, photoluminescence and decay measurements. Using optical absorption spectra, Judd-Ofelt parameters were derived to determine the local structure and bonding in the vicinity of Sm3+ ions. The emission spectra of Sm3+ -doped BiP glass showed two intense emission bands, 4 G5/2 →6 H7/2 (orange) and 4 G5/2 →6 H9/2 (red) for which the stimulated emission cross-sections (σe ) and branching ratios (β) were found to be higher. The quantum efficiencies were also calculated from decay measurements recorded for the 4 G5/2 level of Sm3+ ions. The suitable combination of Bi2 O3 (10mol%) and Sm3+ (0.5mol%) ions in these glasses acted as an efficient lasing material and might be suitable for the development of visible orange-red photonic materials.

Investigation of Green and 1.53 μm emission characteristics of Er3+ doped bismuth phosphate glasses for laser applications

Erbium (Er3+) ion doped bismuth phosphate (BiP) glasses were fabricated by melt quenching technique. In the current project, studied the influence of bismuth content and Er3+ ion doping concentration on photoluminescence (PL) performance and therefore find out the most qualified combination of bismuth and Er3+ for developing compact optical fibre lasers and amplifiers operating at 1.53 μm. Optical absorption measurements are carried out and analysed through Judd-Ofelt (JO) and Mc-Cumber theories from which JO parameters, absorption and stimulated emission cross-sections are determined. The studied glasses show intense and broad visible emission at 545 nm (green) for 4S3/2 → 4I15/2 transition with the excitation 379 nm might be useful for green laser applications. The luminescence behaviour of 4I13/2 → 4I15/2 transition in the wavelength region 1400–1700 nm and its suitability for optical amplifier applications and also for NIR laser have been discussed with parameters such as stimulated emission cross-section (σe), gain bandwidth (ΔG) and optical gain (G). The decay curves for both 4S3/2 (visible) and 4I13/2 (NIR) levels are discussed and they are exhibiting non-exponential nature for all the studied BiP glasses. Among all the BiP glasses, Er-1.0 glass exhibited higher σe, ΔG and G values suggesting the suitability for optical amplifier and NIR laser applications.

Microstructure and spectroscopic investigations of calcium zinc bismuth phosphate glass ceramics doped with manganese ions

Multi-component 10CaF2–20ZnO–(15 − x)Bi2O3–55P2O5:xMnO (0 ≤ x ≤ 2.5) glass ceramics were synthesised by melt quenching technique and heat treatment. The prepared glass ceramics were characterised by XRD, DTA, EDS and SEM. Spectroscopic studies such as optical absorption, EPR, FTIR and Raman were also carried out on these glass ceramics. The XRD and SEM studies have indicated that ceramic samples contain well defined and randomly distributed grains of different crystalline phases. The observed increase of enthalpy from DTA patterns up to 1 mol% of MnO indicates that the crystallisation starts initially from the surface of the material then gradually it is extended to the volume of the material and this influence is meagre at higher concentrations of MnO. The absorption spectra of manganese doped glass ceramics have exhibited two types of conventional bands; one due to Mn2+ ions and other due to Mn3+ ions. The EPR spectra of MnO doped glass ceramics showed a resonance signal around g2 = 2.023 with a six line hyperfine structure and another signal at about g1 = 4.314. The relative intensity and half-width of these two signals are observed to increase with the increase in the concentration of manganese ions up to 1 mol% beyond this concentration it is found to decrease. Such observation indicates the conversion of part of Mn2+ ions into Mn3+ ions in the glass ceramic matrix. The observed increase in the intensity of symmetrical structural units at the expense of asymmetrical structural units from the FTIR and Raman spectra at higher concentration of MnO indicating that Mn2+ ions occupy the network forming positions in the glass ceramic structure.

Gamma rays Interactions with Bismuth Phosphate Glasses Doped with 3d Transition Metal Oxides

Bismuth phosphate glasses of the basic composition (Bi2O3 30 mol%-P2O5 70 mol%) with additional dopants 3d TM oxides (0.2 wt%) were prepared by the melting and annealing technique. Combined optical (UV/vis.) and FT infrared absorption spectra were measured for the prepared samples before and after gamma irradiation with a dose of 8 Mrad (8×104 Gy). Optical spectra reveal strong UV absorption bands due to trace iron impurity together with an additional absorption band due to Bi3+ beside characteristic absorption related to specific 3d TM ions with preference for the lower valences due to the reducing effect of phosphate host glass. FTIR spectra show vibrational bands due to phosphate chains with the sharing of absorption bands due to Bi-O vibrations. Gamma irradiation causes limited changes due to the presence of heavy metal Bi3+ ions which show some shielding behavior towards gamma irradiation as revealed by optical and FT infrared absorption measurements. Some suggested photochemical reactions are forward to interpret the changes in the UV spectra beside the formation of an induced phosphorus oxygen hole center (POHC) in the visible region.

Synthesis and vibrational analysis of new bismuth phosphate glasses

ABSTRACTBismuth phosphate glasses were prepared using the conventional melt quenching technique with a mixture of Bismuth(III) oxide and hydrogen ammonium phosphate. The amorphous state of the samples was verified by X-ray diffraction. The physical parameters like molar volume and oxygen packing density were evaluated from the measured density values. It is found that the density increased from 5.45 g/cm3 to 6.12 g/cm3, while the values of the molar volume increased from 34,97 to 39.08 cm3/mol, and whereas the oxygen packing density decreased with the gradual increase of the of bismuth content. The structure of the glasses was determined using Infrared Spectroscopy. The Fourier Transform Infrared Spectroscopy spectra were recorded in the spectral range from 400 to 1400 cm−1. The structural investigations based on these spectra show the rapid depolymerization of phosphate chains with an increase in bismuth oxide. Also, this investigation highlights that the glassy-matrix contains various phosphate and bismuth structural units. The results indicate that Bismuth oxide plays a network modifier role and stabilizes the structure of the vitreous matrix.

Impact of Bi2O3 on structural properties and lasing effects in Nd3 + doped bismuth phosphate glasses at 1.053 μm emission

Influence of addition of bismuth oxide (Bi2O3) on structural and optical properties of 0.5Nd3+doped different phosphate glasses prepared by melt quenching technique were reported. The structural properties were analysed by FT-IR and 31P MAS NMR techniques. 31P NMR results showed that, with the variation of Bi2O3 concentration in the prepared phosphate glass matrices there was no significant change in the structure. The optical properties have been analysed using Judd–Ofelt (J-O) theory. From absorption spectra, three phenomenological J–O intensity parameters (Ω2, Ω4, Ω6) have been calculated and these parameters were used to estimate the radiative properties. The J-O intensity parameters increased with increase in the concentration of Bi2O3, which confirmed the higher covalency, asymmetry and rigidity. The branching ratios (β) and emission cross-sections (σ) were calculated from the emission spectra of Nd3+ doped bismuth phosphate (BiP) glasses. Among different glass matrices 15mol% of Bi2O3 glass matrix has higher β and σ values which are useful for the laser applications. The improved emission cross-section value with the addition of Bi2O3 content results low threshold and high gain applications. The decay curves of all these BiP glasses showed single exponential behaviour.

Structural and luminescence properties of Dy3+ doped bismuth phosphate glasses for greenish yellow light applications

Different compositions of (5, 10, 15 and 20 mol%) of bismuth and different concentrations (0.5, 1.0, 1.5 and 2.0 mol%) of Dy3+ ion doped bismuth phosphate (BiP) glasses were synthesized by melt-quenching technique. The structural characterization was accomplished by XRD, SEM with EDS, FTIR, FT-Raman and 31P MAS NMR spectroscopy. The optical properties were studied using absorption and photoluminescence spectroscopy. Different structural groups were identified using FTIR and FT-Raman spectra. The depolymerization of metaphosphate chains are described by the decrease of Q2 tetrahedral sites allowing the formation of pyrophosphate groups (Q1) revealed by 31P MAS NMR spectroscopic investigations.Judd-Ofelt intensity parameters Ωλ (λ = 2, 4 and 6) were evaluated from absorption spectra. Radiative parameters such as radiative lifetimes (τR), integrated absorption cross-sections (Σ) and branching ratios (βR) were calculated using Judd-Ofelt intensity parameters. From photoluminescence spectra, experimental branching ratios (βexp) and stimulated emission cross-sections (σP) were calculated for all the observed emission transitions of prepared glasses. The decay profiles for 4F9/2 level were recorded and fit exponential for 0.5 mol% and non-exponential for higher concentrations of Dy3+ due to non-radiative energy transfer among excited Dy3+ ions. The CIE chromaticity co-ordinates have been calculated from the luminescence spectra which confirmed greenish yellow light emission.

Role of titanium ions on the physical and structural properties of calcium zinc bismuth phosphate glass ceramics

The transparent glass ceramics of composition 10CaF2–20ZnO–(15–x)Bi2O3–55P2O5: xTiO2 (0≤x≤4) were prepared by melt quenching followed by heat treatment. The prepared samples were characterized by X-ray diffraction, differential thermal analysis and scanning electron microscopy. These studies have revealed that the samples contain well defined randomly distributed crystalline phases with the complexes of Ti4+ and Ti3+ ions. Spectroscopic studies viz., optical absorption, electron paramagnetic resonance, Fourier transform infrared and Raman were also carried out on these glass ceramics. The results of optical absorption and electron paramagnetic resonance studies revealed that part of the titanium ions exist in Ti3+ state that occupy the tetragonally distorted octahedral sites in the glass ceramic network and these ions are found to increase with an increase in the content of nucleating agent TiO2. Fourier transform infrared and Raman studies indicating the formation of TiO6 structural units along with cross linkages viz., P–O–Bi, P–O–Ti. But when TiO2 is present in the larger quantities, the Π-bond of P=O may be ruptured by TiO4 structural units which may cause the creation of new non-bridging oxygen ions facilitating the formation of [TiO6/2]2− structural units also. Therefore, the analysis of spectroscopic studies indicating that the glass ceramics contain greater than 2mol% of TiO2 is suitable for semiconducting applications.