Er3+-doped germanate glasses for active waveguides prepared by Ag+/K+ ↔ Na+ ion-exchange

Planar waveguides were prepared by Ag⁺/K⁺ ? Na⁺ ion-exchange on Er⁺³-doped GeO₂–ZnO–Na₂O–Li₂O glasses obtained by a melting–casting method. Optical parameters of the waveguides were measured at 543.5, 632.8, and 1550 nm by m-line technique as a function of the Ag⁺ ion-exchange time. The optimized planar waveguides show an effective diffusion depth (d) of 2.95 μm and well confined propagating TE₀ and TM₀ modes at 1550 nm. Spectroscopic properties as photoluminescence emission and emission decay time were evaluated for the erbium-doped planar waveguide, indicating that Ag⁺ ? Na⁺ ion-exchange enhance the photoluminescence emissions in the green and infrared regions from erbium ions. The glass system studied is promising to be applied as optical amplifiers in the C-telecom band. Green emission sensitized by Ag⁺ was also observed.     

2 μm spectroscopic investigation of Tm3+-doped tellurite glass fiber

TmF₃ doped TeO₂–ZnO–La₂O₃ (TZL) glasses and fibers have been prepared by the conventional melt-quenching and suction casting methods, respectively. 2 μm emission properties and energy transfer mechanisms of the TZL glasses and fibers have been analyzed and discussed. The oscillator strength, Judd–Ofelt parameters, radiative transition probability and radiative lifetime of Tm³⁺ have been calculated based on the absorption spectra and Judd–Ofelt theory. The maximum emission cross-section of Tm³⁺ is 6.9 × 10^?21 cm² near 2 μm. Emission spectra have been obtained from both TZL fibers and bulk glass when excited with a 794 nm pump. The results of 2 μm emission spectra indicate that the line width of Tm³⁺ measured in fibers is narrower than that in the bulk glass sample. The peak position of the emission spectra shifts to longer wavelength with increment of the fiber length.     

Formation of Co2+-doped nanocrystals in La2O3–MgO–Al2O3–SiO2 glass-ceramics

Transparent glass-ceramics were synthesized by heat-treatment of glass with a composition of 5La₂O₃–13.2MgO–28.8Al₂O₃–46SiO₂–4.5TiO₂–2.5ZrO₂–0.15CoO (LMAS) (wt.%). The activation energy of crystallization and the Avrami parameter for the LMAS glass were determined from the DTA curves at different heating rates. The most two intense bands of Raman spectrum of initial glass at ~ 810 cm^?1 and ~ 900 cm^?1 were connected with the presence of [SiO₄] and [TiO₄] tetrahedral, respectively. After heat-treated at 700 °C/10 h+820 °C/8 h, the intensity of the band for [TiO₄] tetrahedral weakened, while an intensive band at ~ 800 cm^?1 for the Ti–O bond appeared. Other bands were characteristics of high-silicate network and x(MgTi₂O₅)·y(Al₂TiO₅) polycrystals. The changes reflected phase separation after heat-treatment of the initial glass. The strong absorption band of glass-ceramics centered at 580 nm can be assigned to ⁴A₂(⁴F)→⁴T₁(⁴P) and the broad absorption band at 1100–1700 nm to ⁴A₂(⁴F)→⁴T₁(⁴F) transitions of tetrahedral coordinated Co²⁺ ion. Two broad emission bands, one was around 660 nm, the other was from 800 nm to 1050 nm, of glass-ceramics correspond to the ⁴T₁(⁴P)→⁴A₂(⁴F) and ⁴T₁(⁴P)→⁴T₂(⁴F) transitions of tetrahedral coordinated Co²⁺ ions. The absorption and emission features clearly demonstrated that Co²⁺ ions were incorporated into nanocrystals and located in tetrahedral sites.     

Enhanced 2.0 μm emission and energy transfer in Yb3+/Ho3+/Ce3+ triply doped tellurite glass

Ce³⁺ induced enhancement of Ho³⁺ ~ 2.0 μm emission in Yb³⁺/Ho³⁺ codoped sodium–zinc–tellurite (TNZ) glass was achieved under 980 nm LD laser excitation. The spectroscopic studies show that the upconversion is remarkably reduced by the presence of Ce³⁺. The ~ 2.0 μm fluorescence intensity is nearly triply enhanced, and the energy transfer efficiency from Yb³⁺ to Ho³⁺ is improved from 16.1% to 42.6% by increasing the Ce³⁺ concentration from 0 to 0.8 mol%. The mechanism responsible for the upconversion reduction and ~ 2.0 μm emission enhancement in Yb³⁺/Ho³⁺/Ce³⁺ triply-doped TNZ glass is also discussed. Our results indicate that the Yb³⁺/Ho³⁺/Ce³⁺ triply-doped TNZ glass is a promising candidate material for improving the Ho³⁺ 2.0 μm fiber laser performance.     

Synthesis and photoluminescence of Eu3+-doped ZnO–Ga2O3–SiO2 nano-glass-ceramics

Transparent rare-earth Eu³⁺-doped ZnO–Ga₂O₃–SiO₂ nano-glass-ceramics were obtained by a sol–gel method. X-ray diffraction and transmission electron microscopy were used to characterize the as-synthesized materials. Results showed that ZnGa₂O₄ nanocrystals with the size of 5 nm were precipitated from ZnO–Ga₂O₃–SiO₂ system and dispersed in the SiO₂-based glass when the heat-treatment temperature was up to 800 °C. Photoluminescence characterization of Eu³⁺-doped ZnO–Ga₂O₃–SiO₂ nano-glass-ceramics was carried out and the results show that the as-synthesized material display intense emission at 615 nm belonging to ⁵D₀ → ⁷F₂ transition.     

Emissions of 1.20 and 1.38 μm from Ho3+-doped lithium–barium–bismuth–lead oxide glass for optical amplifications

Efficient infrared emissions at 1.20 μm [⁵I₆ → ⁵I₈ transition] and 1.38 μm [(⁵ F₄, ⁵ S₂) → ⁵I₅ transition] from Ho³⁺-doped lithium–barium–bismuth–lead (LBBP) glass were observed. The stimulated emission cross-sections were calculated to be 0.29 × 10^?20 and 0.25 × 10^?20 cm² for 1.20 and 1.38 μm emissions, respectively. Judd-Ofelt characteristic parameters Ω₂, Ω₄ and Ω₆ for Ho³⁺ in LBBP glass were calculated to be 6.72 × 10^?20, 2.35 × 10^?20 and 0.61 × 10^?20 cm², respectively, which indicates a strong asymmetry and a covalent environment between the Ho³⁺ ions and the ligands in this glass. The optical amplifications operating at these relatively unexplored wavelength regions were evaluated and discussed.     

Spectroscopic properties of the 1.8 μm emission of Tm3+/Yb3+ codoped TeO2–ZnO–Bi2O3 glasses with efficient energy transfer

Tm³⁺-doped and Tm³⁺/Yb³⁺-codoped TeO₂–ZnO–Bi₂O₃ (TZB) glasses are prepared by melt-quenching method. The Judd-Ofelt intensity parameters (Ω_t t = 2, 4, 6), radiative transition rate, and radiative lifetime of Tm³⁺ are calculated based on the absorption spectra. The 1.8 μm emission of the samples is investigated under 980 nm laser excitation. The absorption, emission cross-sections, and gain coefficient of Tm³⁺:³F₄ → ³H₆ are calculated. The energy transfer processes of Yb³⁺–Yb³⁺ and Yb³⁺–Tm³⁺ are analyzed, the results show that the Yb³⁺ ions can transfer their energy to Tm³⁺ ions with large energy transfer coefficient, and a maximum efficiency of 79%.     

Mössbauer Study of the Effect of Cation Substitutions on the Magnetic Phase Transitions in BiFe1 – xCrxO3 and (1 – x)BiFeO3–xPbFe0.5Sb0.5O3 Solid Solutions

Crystallography Reports - The concentration dependences of the magnetic phase transition temperature TN, determined based on the changes in Mössbauer spectra, were investigated for a BiFeO3...     

Growth of Sm1 – ySryF3 – y (0 < y ≤ 0.31) Crystals and Investigation of Their Properties

Crystallography Reports - Sm1&nbsp;–&nbsp;ySryF3&nbsp;–&nbsp;y (0 &lt; y ≤ 0.31) crystals have been grown from melt by directional solidification in a...     

Sol–gel synthesis and photoluminescence of RE3BO6: Eu3+/Tb3+ (RE = Y, Gd) microcrystalline phosphors from hybrid precursors

Novel phosphors of Eu³⁺/Tb³⁺ doped RE₃BO₆ (RE = Y, Gd) have been prepared using an original modified in situ sol–gel synthesis route. Different optimized organic media were mixed with rare earth coordination polymers, and tri-n-butyl borate was added to assemble inorganic/organic multi-component hybrid precursors. After calcinations of the resulting precursors at 1000 °C, target phosphors were obtained. The microstructure and morphology information of the phosphors were investigated via the technique of X-ray powder diffraction (XRD) and scanning electronic microscopy, and it has been shown that these phosphors present symmetrical distribution and high packing density, whose grain sizes were around 200 nm. Analyzed by luminescent spectra, these phosphor particles show narrow lines of emissions respectively originating from their characteristic transitions, and the dominating emission peak is due to the hypersensitive transition. The RE₃BO₆: Eu³⁺/Tb³⁺ (RE = Y, Gd) phosphors can be expected to gain more practical applications in commercial phosphors and other luminescent materials used in advanced devices.     

Effects of Fe2O3 replacement of ZnO on elastic and structural properties of 80TeO2–(20 − x)ZnO–xFe2O3 tellurite glass system

Ternary tellurite glasses with the chemical formula 80TeO₂–(2 ? x)ZnO–xFe₂O₃ (x = 0–15 mol%) have been prepared by the melt-quenching method. Elastic and structural properties of the glasses were investigated by measuring both longitudinal and shear velocities using the pulse-echo overlap method at 5 MHz and Fourier transform infrared (FTIR) spectroscopy, respectively. Both longitudinal and shear velocity showed a large increase of 3.40% and 4.68%, respectively, at x = 5 mol% before a smaller increase for x > 5 mol%. Interestingly, longitudinal modulus (L), shear modulus (G), bulk modulus (K) and Young's modulus (E) recorded similar trends with increase in Fe₂O₃. The initial large increases in shear and longitudinal velocity and related elastic moduli observed at x = 5 mol% are suggested to be due to structural modification which enhances rigidity of the glass network. FTIR analysis showed increase in bridging oxygen (BO) as indicated by the relative intensity of the TeO₄ assigned peaks and increase in intensity of the FeO₆ assigned peak (~ 451 cm^? 1) which indicates that Fe acts as a modifier in the glass network. The increase in rigidity of the glass system is suggested to be due to the increase of BO together with the formation of strong covalent FeO bond. Quantitative analysis based on the bulk compression and ring deformation models showed that the k_bc/k_exp value decreased gradually from 2.41 (x = 0 mol%) to 2.02 (x = 15 mol%) which infers that the glass system became a relatively more open 3D network as Fe₂O₃ was increased.     

Production and properties of high purity TeO2− WO3−(La2O3, Bi2O3) and TeO2− ZnO−Na2O−Bi2O3 glasses

TeO₂–WO₃ (TW), TeO₂–WO₃–La₂O₃ (TWL), TeO₂–WO₃–La₂O₃–Bi₂O₃ (TWLB) and TeO₂–ZnO–Na₂O–Bi₂O₃ (TZNB) glasses were produced by high-purity oxide mixtures melting in platinum or gold crucible at 800 °C in the atmosphere of purified oxygen. The total content of Cu, Mn, Fe, Co and Ni impurities was not more than 0.1–0.5 ppm wt in the initial oxides and glasses. The stability of TZNB glasses to crystallization, characterized by (T_x ? T_g) value more than 150 °C, was demonstrated by DSC measurements at heating rate 10 K/min. In the case of La₂O₃-containing glasses the thermal effects of both crystallization and fusion of the crystallized phases were not observed. The hydroxyl groups absorption coefficients of pure tellurite glasses at the maximum of the absorption band (λ ~ 3 μm) were in the region of 0.012–0.001 cm^?1. The optical absorption losses, measured by the laser calorimetry method at λ = 1.56 and 1.97 μm, did not exceed 100 dB/km.     

Optimization of the Compositions of Solid Electrolytes Cd1 – xRxF2 + x (R = La–Lu,Y) with a Fluorite-Type Structure for Conductivity and Thermal Stability

Crystallography Reports - Optimization of the compositions of Cd1–xRxF2+x nonstoichiometric phases (CaF2 type, R is a rare-earth element) for the ionic conductivity and thermal stability is...     

Synthesis and Structural Study of the Cu2ZnSn1 – xSixSe4 System

Crystallography Reports - The quaternary semiconductor compounds Cu2ZnSnSe4, Cu2ZnSiSe4, and Cu2ZnSn1&nbsp;–&nbsp;xSixSe4 solid solutions on their basis have been synthesized from the...     

Nanostructured Crystals of Fluorite Phases Sr1 – xRxF2 + x (R Are Rare-Earth Elements) and Their Ordering. 13: Crystal Structure of SrF2 and Concentration Dependence of the Defect Structure of Nonstoichiometric Phase Sr1 – xLaxF2 + x As Grown (x = 0.11, 0.20, 0.32, 0.37, 0.47)

Crystallography Reports - The defect structure of as-grown SrF2 and nonstoichiometric phases Sr1&nbsp;–&nbsp;xLaxF2&nbsp;+&nbsp;x (x = 0.11, 0.20, 0.32, 0.37, 0.47) single...     

Synthesis and X-ray Diffraction Analysis of Cu2CdGexSn1 – xSe4 Solid Solutions

Crystallography Reports - The high-temperature orthorhombic phase of Cu2CdGeSe4 quaternary compound, tetragonal phase of Cu2CdSnSe4 compound, and Cu2CdGexSn1&nbsp;–&nbsp;xSe4 solid...     

Spectroscopic properties of Co2+ ions in La2O3–MgO–Al2O3–SiO2 glass-ceramics

Co²⁺-doped La₂O₃–MgO–Al₂O₃–SiO₂ (LMAS) glass-ceramics was synthesized by conventional method. The microstructure of LMAS GCs heat-treated at 760 °C/12 h + 930 °C/4 h was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The spectroscopic properties of Co²⁺-doped LMAS GCs were studied by absorption spectrum, excitation spectrum, and temperature dependent luminescence spectra. XRD results revealed the sizes of MgAl₂O₄ crystalline phases are about 9.1 ± 1.5 nm. The three peaks in the visible absorption band of LMAS GCs at 549 nm, 585 nm and 626 nm are connected with the transitions from ⁴A₂ level to ²A₁/²T₂(²G), ⁴T₁(⁴P) and ²E/²T₁(²G) levels, respectively, and excitations into them emit the radiation at around 666 nm. The luminescence intensity increased with temperature increasing from 10 K to 150 K, while it weakened with temperature increasing from 150 K to 350 K. These features were explained by the effects of two competing mechanisms.