Spectroscopic properties of Eu3+/Nd3+ co-doped phosphate glasses and opaque glass–ceramics

This paper reports the fabrication and characterization of Eu³⁺/Nd³⁺ co-doped phosphate (PNE) glasses and glass–ceramics as a function of Eu³⁺ concentration. The precursor glasses were prepared by the conventional melt quenching technique and the opaque glass–ceramics were obtained by heating the precursor glasses at 450 °C for 30 h. The structural and optical properties of the glass and glass–ceramics were analyzed by means of X-ray diffraction, Raman spectroscopy, UV–VIS–IR absorption spectroscopy, photoluminescence spectra and lifetimes. The amorphous and crystalline structures of the precursor glass and opaque glass–ceramic were confirmed by X-ray diffraction respectively. The Raman spectra showed that the maximum phonon energy decreased from 1317 cm⁻¹ to 1277 cm⁻¹ with the thermal treatment. The luminescence spectra of the glass and glass–ceramic samples were studied under 396 nm and 806 nm excitation. The emission intensity of the bands observed in opaque glass–ceramic is stronger than that of the precursor glass. The luminescence spectra show strong dependence on the Eu³⁺ ion concentration in the Nd³⁺ ion photoluminescence (PL) intensity, which suggest the presence of energy transfer (ET) and cross-relaxation (CR) processes. The lifetimes of the ⁴F_3/2 state of Nd³⁺ ion in Eu³⁺/Nd³⁺ co-doped phosphate glasses and glass–ceramics under 806 nm excitation were measured. It was observed that the lifetimes of the ⁴F_3/2 level of Nd³⁺ of both glasses and glass–ceramics decrease with the increasing Eu³⁺ concentration. However in the case of opaque glass–ceramics the lifetimes decrease only 16%.     

Spectroscopic studies of TeO<Subscript>2</Subscript>–ZnO–Er<Subscript>2</Subscript>O<Subscript>3</Subscript> glass system

Series of glass based on the (80 − x)TeO₂–20ZnO–(x)Er₂O₃ system (0.5 mol% ≤ x ≤ 2.5 mol%) has successfully been made by melt quenching technique. The optical properties of glass have been investigated by means of IR and Raman spectroscopy. It is observed that as the Er₂O₃ content is being increased, the sharp IR absorption peaks are consistently shifted from 650 to 672 cm⁻¹ while the Raman shift intensity around 640–670 cm⁻¹ is decreases but increases around 720–740 cm⁻¹. It is found out that both phenomenons are related to the structural changes between the stretching vibration mode of TeO₄ tbp and TeO₃ tp, and bending vibration mode of Te–O bonds in the glass linkages.     

Crystallization of R2O–MgO–Al2O3–B2O3–SiO2–F (R=K+, Na+) glasses with different fluorine source

The effect of fluorine source on the crystallization behaviors of the R₂O–MgO–Al₂O₃–B₂O₃–SiO₂–F (R=K⁺, Na⁺) glasses is studied by differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectrum. Two glasses with the same composition were prepared by using NaF and MgF₂ as the source of fluorine, respectively. The glass with the fluorine source of NaF is quite stable during heat-treatment. Only large dendrite crystals form on the surface of this glass, while the interior of the glass still remains amorphous. In contrast, the glass with the fluorine source of MgF₂ exhibits uniform bulk crystallization and forms mica-containing glass-ceramics after heat-treatment. The structure difference between these two glasses was investigated by Raman spectrum. The glass with the fluorine source of NaF shows a simple Raman spectrum. Boroxol rings are found to be the dominant unit in this glass. In contrast, multiple peaks appear on the Raman spectrum of the glass with the fluorine source of MgF₂, and these peaks are resolved to the vibrations of three- or four-coordinated boron units, such as chain-type metaborate groups, pentaborate groups, diborate groups, highly changed orthoborate groups, pyroborate groups, as well as boroxol rings. The stability of the glass with the NaF fluorine source is attributed to the high stability of the boroxol rings in this glass.     

Preparation and structural studies in the (70 − x)TeO2–20WO3–10Li2O–xLn2O3 glasses

Quaternary tellurite glass systems (70 ? x)TeO₂–20WO₃–10Li₂O–xLn₂O₃ where x = 0, 1, 3 and 5 mol% and Ln are La, Pr, Nd, Sm, Er and Yb, respectively, have been prepared by the melt quenching technique. Densities of the obtained glasses were measured and the molar volume was calculated. IR absorption spectra of the present glass systems were determined at room temperature over the range of wavenumbers from 400–1,600 cm^?1. Raman spectra of the present glass samples were measured in the range of 30–1,030 cm^?1. Density, molar volume, IR and Raman spectra of the glasses were discussed by calculating average cross-link density, packing density, theoretically calculated Poisson’s ratio and number of bonds per unit volume of the studied glasses. Also, the quantitative interpretations were based on concentration of ions per unit volume of Te, Ln and O, short distance in nanometre between ions for (Te–O) of TeO₄ and TeO₃ groups, (W–O) of WO₄, WO₆ groups and calculated wavenumber, $ \bar{\upsilon } $ , for TeO₄ and TeO₃, respectively. The average stretching force constant that present in these quaternary glasses has been calculated in order to interpret the data obtained.     

Structure and ac conductivity of sodium–lead–cadmium metaphosphate glasses

Sodium–lead–cadmium phosphate glasses having a mol% composition (40−y)Na₂O–yCdO–10PbO–50P₂O₅ (0≤y≤40) were prepared by using the melt–quench technique. They have been characterised by infrared spectroscopy, Raman spectroscopy and ³¹P magic angle spinning nuclear magnetic resonance (MAS-NMR). Infrared and Raman spectroscopies reveal the formation of P–O–Pb and P–O–Cd bonds, which replace P–O–⁺Na bonds. MAS-NMR spectroscopy shows that no metaphosphate network depolymerisation occurs when y increases. Thus, both PbO and CdO act as the network modifiers. Systematic variations of the glass transition temperature, density, and molar volume observed are in agreement with these results. Ionic conductivity is correlated to the structural model.     

Characterisation of Ga2O3–Na2O–CaO–ZnO–SiO2 bioactive glasses

The structural role of Gallium (Ga) is investigated when substituted for Zinc (Zn) in a 0.42SiO₂–0.40–xZnO–0.10Na₂O–0.08CaO glass series, (where x = 0.08). Each starting material was amorphous, and the network connectivity (NC) was calculated assuming Ga acts as both a network modifier (1.23), and also as a network former. Assuming a network forming role for Ga the NC increased with increasing Ga concentration throughout the glass series (Control 1.23, TGa-1 2.32 and TGa-2 3.00). X-ray photoelectron spectroscopy confirmed both composition and correlated NC predictions. Raman spectroscopy was employed to investigate Q-structure and found that a shift in wavenumbers occurred as the Ga concentration increased through the glass series, from 933, 951 to 960 cm^?1. Magic angle spinning nuclear magnetic resonance determined a chemical shift from ?73, ?75 to ?77 ppm as the Ga concentration increased, supporting Raman data. These results suggest that Ga acts predominantly as a network former in this particular Zn-silicate system.     

Spectroscopic analysis of a novel Nd3+-activated barium borate glass for broadband laser amplification

Spectroscopic parameters of a novel Nd³⁺-activated barium borate (BBONd) glass have been analyzed for broadband laser amplification. The Judd–Ofelt (JO) intensity parameters were determined through a systematic analysis of the absorption spectrum of Nd³⁺ ions in the BBONd glass. High values of the JO intensity parameters reveal a great centro-symmetrical loss of the Nd³⁺ sites and high covalency degree of the ligand field. The very high Ω₆ intensity parameter value makes evident both a great structural distortion of the Nd³⁺ sites and a strong electron–phonon coupling between Nd³⁺ and free OH⁻ ions, which is consistent with the phonon energy maximum (3442.1 cm⁻¹) recorded by Raman spectroscopy. This strong electron–phonon coupling favors high effective bandwidth and gain bandwidth values of the laser emission (⁴F_3/2 → ⁴I_11/2) of Nd³⁺ ions. The electric-dipole oscillator strengths of all the Nd³⁺ absorption transitions, and in particular that of the hypersensitive transition (⁴I_9/2 → ⁴G_5/2), are enhanced by this great structural distortion of the host. Broadband laser amplification of the ⁴F_3/2 → ⁴I_11/2 emission (1062 nm) of Nd³⁺ ions in the BBONd glass pumped at 805 nm (⁴I_9/2 → ⁴F_5/2 + ²H_9/2) is evaluated through the main fluorescent parameters in competition with non-radiative processes. In general, the BBONd glass exhibits spectroscopic parameters comparable with those reported in the literature for broadband laser amplification into the IR region.     

Spectroscopic characterisation of local structure in Y<Subscript>2</Subscript>O<Subscript>3</Subscript>–B<Subscript>2</Subscript>O<Subscript>3</Subscript>–Bi<Subscript>2</Subscript>O<Subscript>3</Subscript> glasses doped with gadolinium

Gadolinium doped bismuth borate glasses containing up to 30 mol% Y₂O₃ were prepared by fast melt quenching method. The effect of yttrium on the local order in 3B₂O₃ · Bi₂O₃ and B₂O₃ · Bi₂O₃ glass matrices, particularly on the bismuth sites, was investigated by infrared (IR) spectroscopy and electron paramagnetic resonance (EPR) of Gd³⁺ ions. The IR results show that the local structure is more ordered in the glass system with higher bismuth content and the progressive addition of yttrium increases the local disorder in both bismuth–borate glass matrices. The EPR results indicate that Gd³⁺ ions occupy both bismuth and yttrium sites and reflect the same structural disorder like that suggested by IR results.     

Influence of the heat treatment procedure and irradiation on the structure of the anionic motif and crystallization of uranium-containing phosphate glasses

The solubility of UO₃ in sodium almino(ferro)phosphate (SAFP) glasses prepared by quenching of melts reaches almost 50 wt %. The structure of the anionic motif of the network of such glasses is formed by polyanions and consists of alumino(ferro)phosphate and uranium–oxygen constituents. Irradiation with electrons of up to 8 MeV energy to an absorbed dose of 10⁶ Gy does not lead to appreciable changes in the glass structure, except insignificant increase in the fraction of octahedrally coordinated aluminum. After annealing, samples of sodium aluminophosphate glasses with low content of uranium oxides (up to 10 wt %) partially crystallize with the formation of phosphotridymite, whereas high-uranium glasses (up to ~50 wt % UO₃) remain X-ray amorphous. Samples of SAFP glasses at low concentrations of uranium oxides remain amorphous and at high concentrations undergo phase segregation with the formation of a SAFP glass phase enriched in uranium oxides and crystalline phase of sodium aluminum iron orthophosphate Na₃(Al,Fe)₂(PO₄)₃ containing impurity amounts of uranium ions. The incorporation of uranium ions is most probably due to the occurrence of redox processes between uranyl and iron ions.     

Structural, Spectroscopic Studies and Magnetic Properties of Doped Sillenites-Type Oxide Bi12[M]O20 M=Fe, Co

Layered structure of sillenites-type oxides Bi₁₂MO₂₀, the M position can be occupied by tetravalent or trivalent cations. This study focuses in Bi₁₂MO₂₀, M=Co, Fe, and Co/Fe, polycrystalline samples which are prepared by the solid-state reaction method. Infrared (IR) optical absorption, Raman scattering, and Foner magnetometer (BS2) techniques were used for systematic characterization of sillenite type oxide. IR and Raman scattering results showed the appearance of a band, at 850 cm^?1 and at 680 cm^?1, attributed to the (MO₄)^?3. Magnetic susceptibility measurements of all samples were done in a temperature range 2–300 K. The interaction of the M cations with each other through M–O–M linkages of approximately 180^° is expected to be dominant, and this would be paramagnetic in nature.     

Synthesis and optical properties of a lithium niobiosilicate glass doped with europium

The sol–gel method was used to prepare a lithium niobiosilicate glass doped with europium ions, 91SiO₂–4Li₂O–4Nb₂O₅–1Eu₂O₃ (% mole). The dried gel was heat-treated between 500 °C and 750 °C and glass ceramics were obtained. X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman studies show that crystallization starts at temperatures above 600 °C. The LiNbO₃ and EuNbO₄ nanocrystals were found in the heat-treated samples as corroborated by the structural, morphological and optical properties. Room temperature photoluminescence (PL) studies allow us the identification of multiple Eu-related optical centres and the strongest red ⁵D₀ → ⁷F₂ intraionic transitions occur in the samples heat-treated at 600 °C where the LiNbO₃ crystal phase was detected.     

Spectroscopic characterization of alkali borosilicate glasses containing iron ions

Structural properties of alkali borosilicate glasses containing iron ions were investigated using infrared, laser Raman and Mössbauer spectroscopy. Two types of glasses were prepared: SRL-type with the composition 18.5 wt% Na₂O, 10.0 wt% B₂O₃, 52.5 wt% SiO₂, 4.0 wt% Li₂O, 10 wt% TiO₂ and 5.0 wt% CaO, and sodium borosilicate glass with the composition 16.7 wt% Na₂O, 18.7 wt% B₂O₃ and 64.6 wt% SiO₂. Raman spectroscopy showed that orthosilicates are the dominant amorphous phase in the SRL-type of glass. Incorporation of iron in the SRL-type of glass induced polymerization of silicate units and -Si-O-Fe- copolymerization. It was concluded that different amorphous phases are simultaneously present in the SRL-type of glass containing iron ions. Interpretation of the Raman spectra is given. Incorporation of iron ions into the sodium borosilicate glass also affected the corresponding IR spectra. The valence state of iron and its coordination were determined by⁵⁷Fe Mössbauer spectroscopy.     

IR transparency of the glass of ZnCl2-KBr-PbBr2 system

IR transparency and some properties of halide glass of composition 48ZnCl₂-48KBr-4PbBr₂ (mol%) have been investigated as the basic study on the development of IR glass fiber for CO₂ gas laser. The glass transition temperature Tg, crystallization temperature T_c, softning temperature T_s, and linear thermal expansion coefficient α of the glass were found to be 45–46°C, 100°C, 54°C, and 570×10^?7 / °C, respectively. The refractive index of the glass for He-Ne laser emission (632.8 nm) was about 1.63. The amount of impurity which decreases the transmissibility for CO₂ laser beam due to the absorption in the wavelength region 10–11 μm could be reduced by preparing the glass from a batch containing NH₄ Cl under reactive atmosphere of CCl₄ or CBr₄ in a glove box filled with He gas of dew point ?62～ ?45°C. The minimum value of absorption loss of the glass for CO₂ gas laser measured by laser calorimetry was about 20 dB/m.     

Study on Raman line at 1080.2 cm in ZnO thin films prepared under high RF power

ZnO thin films were prepared on glass or on homo-buffer/glass by a RF magnetron sputtering method at RF power of 100-550 W. The structural and Raman characteristics of the films were analyzed by X-ray diffraction and Raman scattering. There appeared a sharp peak of 1080.2 cm⁻¹ near the A₁(2LO) mode (1156 cm⁻¹) of ZnO in the Raman spectra when the RF power was higher than 300 W. In this case, the (100) peak of ZnO film appeared obviously. It was speculated that the Raman mode at 1080.2 cm⁻¹ was induced by the ordered distribution of Zn_i defects in ZnO lattice.     

Physical and spectroscopic properties of multi-component Na2O–PbO–Bi2O3–SiO2 glass ceramics with Cr2O3 as nucleating agent

Transparent glass ceramics, synthesized from melt quenching followed by heat treatment, of the composition 10Na₂O–30PbO–10Bi₂O₃–(50 − x)SiO₂:xCr₂O₃ (mol%), where 0 ⩽ x ⩽ 0.5, were characterized with XRD, DTA, SEM and EDS. Physical and spectroscopic studies, viz., optical absorption, electron paramagnetic resonance (EPR), FTIR and Raman were investigated. The characterization of the host glass ceramic has revealed that the formation of a major phase of sodium silicate along with two minor phases such as lead silicate and bismuth oxide. By integrating Cr₂O₃ to the host glass additional crystal phases viz., NaCrO₂, Na₂Cr₂O₇ and Pb(CrO₄) which are the complexes of Cr³⁺ and Cr⁶⁺ ions were also developed. As the concentration of nucleating agent is increased, a part of the Cr⁶⁺ ions is found to reduce in to Cr³⁺ ions. Spectroscopic studies have revealed that with an increase in the concentration of Cr₂O₃ from 0.1 to 0.5 mol%, there is a gradual increase in the intensity of vibrational modes of various asymmetric structural units of silicate, bismuthate and chromate in the glass ceramic network at the expense of symmetrical structural units. The analysis of the results of these studies has indicated that in the samples containing higher concentration of Cr₂O₃, chromium ions exists predominantly in Cr³⁺ state and occupy the octahedral positions in glass ceramic matrix and such glass ceramic samples are suitable for lasing action.     

Studies on boro cadmium tellurite glasses

To investigate the modification effect of the modifier CdO on boro tellurite glass, a series of glasses with compositions (50 − x) CdO-xTeO₂-50B₂O₃ have been prepared by conventional melt quenching technique. Optical absorption, IR and Raman structural studies are carried out on the glass system. The optical absorption studies revealed that the cutoff wave length and refractive index increase while optical band gap (E_opt) and Urbach energy decreases with increase of CdO content. The IR and Raman studies revealed that structure of glass network consists of [TeO_3]/[TeO₃₊₁], [TeO₄], [BO₃], [BO₄] and [Cd-Te] linkages .The compositional dependence of different physical parameters such as density, molar volume, oxygen packing density, optical basicity, have been analyzed and discussed.     

Influence of Ga3+ ions on spectroscopic and dielectric features of multi component lithium lead boro bismuth silicate glasses doped with manganese ions

Multi-component glasses of the chemical composition 19.5Li₂O–20PbO–20B₂O₃–30SiO–(10 − x)Bi₂O₃–0.5MnO:xGa₂O₃ with 0 ≤ x ≤ 5.0 have been synthesized. Spectroscopic (optical absorption, IR, Raman and ESR) and dielectric properties were investigated. Optical absorption and ESR spectral studies have indicated that managanese ions do exist in Mn³⁺ state in addition to Mn²⁺ state in the samples containing low concentration of Ga₂O₃. The IR and Raman studies indicated increasing degree of disorder in the glass network with the concentration of Ga₂O₃ up to 3.0 mol%. The dielectric constant, loss and ac conductivity are observed to increase with the concentration of Ga₂O₃ up to 3.0 mol%. The quantitative analysis of the results of dielectric properties has indicated an increase in the insulating strength of the glasses as the concentration of Ga₂O₃ is raised beyond 3.0 mol%. This has been attributed to adaption of gallium ions from octahedral to tetrahedral coordination.     

Phase Composition,Structure, and Hydrolytic Durability of a Uranium-Containing Magnesium Potassium Phosphate Compound

Uranium-containing samples of magnesium potassium phosphate (MPP) compound were synthesized using a nitric acid uranium solution. Uranium is incorporated in the MPP compound in the form of potassium uranyl phosphate with the structure of metaankoleite natural mineral, K(UO₂)PO₄·3H₂O. The differential and integral uranium leach rates, determined in accordance with GOST (State Standard) R 52 126–2003 on the 28th day of contact of the compound with water, are 1.7 × 10^–6 and 2.7 × 10^–6 g cm^–2 day^–1, respectively, and the degree of leaching is 0.014%. High hydrolytic durability of the compound with respect to uranium leaching reduces the risk of release of uranium isotopes from radioactive waste into the environment.     

Environment segregation of Er3+ emission in bulk sol–gel-derived SiO2–SnO2 glass ceramics

Er-doped (100-x) SiO₂–x SnO₂ glass–ceramic monoliths were prepared using a sol–gel method. Raman spectroscopic measurements showed the structural evolution of the silica matrix caused by the formation and the growth of SnO₂ nanocrystals. Analysis of the photoluminescence properties shows that the quantity of Er³⁺ ions embedded in the vicinity of SnO₂ nanocrystals could be controlled by the SnO₂ concentration. We give spectroscopic evidence of energy transfer to erbium ions provided by SnO₂ nanocrystals in the silica matrix. The ⁴I_13/2 level decay curves present a double-exponential profile with two lifetimes associated to rare-earth ions in two different environments.     

Effect of quenching rate on the structure, ion transport, and crystallization kinetics in lithium-rich phosphate glass

The report investigates the effect of quenching rate on the structure, lithium ion dynamics, and crystallization kinetics of mol% 60Li₂O–40P₂O₅ glass. Quenching rate of the order of 10⁵ K s^?1 has been achieved using a twin-roller rapid quenching setup. Raman and FT-IR studies reveal that the rapidly quenched glass is more disordered with a reduced amount of pyrophosphate structural units (P₂O₇ ^4?) in the glass matrix as compared with the conventionally quenched glass. Non-isothermal differential scanning calorimetry brings out that the rapidly quenched glass undergoes three-phase crystallization while the conventionally quenched glass depicted predominantly single-phase crystallization. The phases are identified as lithium metaphosphate (LiPO₃), pyrophosphate (Li₄P₂O₇), and orthophosphate (Li₃PO₄). The activation energy for crystallization for the major phase Li₄P₂O₇ calculated using thermoanalytical methods turns out to be 287 kJ mol^?1. The above structural differences between the rapidly and conventionally quenched glasses result in superior conduction characteristics for the rapidly quenched glass depicting ionic conductivity of 1.0 × 10^?6 S cm^?1 at 343 K with an activation energy of 0.63 eV for lithium ion motion. Microstructural studies on the glass ceramics divulge surface, 2D, and 3D crystal growth mechanism for lithium meta-, pyro-, and ortho-phosphate phases, respectively.