Bi2O3 GeO2 Research Articles

Broadband photoluminescence of Bi2O3–GeO2 binary systems: glass, glass-ceramics and crystals

Ultra-broadband emission covering 1000–1800 and 1800–3020 nm of Bi2O3–GeO2 binary system materials, from glass to glass-ceramics to crystals, is presented in this paper. This is the first time, to our best knowledge, that broadband photoluminescence of BGO crystals (including Bi4Ge3O12 and Bi12GeO20) in the range of 1800–3020 nm has been realized. HRTEM, XPS and XANES have been used to investigate the effects of the valence states and the structure environment of bismuth on the emission properties of Bi2O3–GeO2 binary system materials. Bi2+ and Bi+ are proposed as the emission centers of the photoluminescence peaks at 1060 and 1300 nm, respectively. The broadband emission from 1800 to 3020 nm originates from bismuth clusters. Bi2O3–GeO2 binary system materials could be promising laser materials in the field of full-band optical fiber communication amplifiers, ultra-fast lasers and diode pumped solid state lasers, due to their broadband emission spectra and their feasibility of synthesis and drawing into fibers.

Glass formation and Raman scattering studies of bismuthate glasses within Bi2O3–GeO2–BaO pseudo-ternary system

Glass forming region of Bi2O3–GeO2–BaO (BGB) pseudo-ternary system is determined by melt quenching method. Glass density and refractive index decrease as BaO was introduced in the BGB glasses, while Raman scattering intensity shows a contrary tendency. By analyzing the Raman scattering spectra, the structural units existing in BGB network are specified, and the evolution of glass structures with incorporation of BaO is presented.

Enhanced 2 μm broad-band emission and NIR to visible frequency up-conversion from Ho3+/Yb3+ co-doped Bi2O3–GeO2–ZnO glasses

In this work, a new and non-conventional oxide glass composition based on Bi2O3–GeO2–ZnO system has been formulated with an aim to realize low phonon oxide glass and elucidate its performance when co-doped with Ho3+/Yb3+ for the energy transfer based NIR emission at 2μm from Ho3+ ions under Yb3+ excitation. The glass with 1.0mol% Ho2O3 and 0.5mol% Yb2O3 has exhibited maximum energy transfer rate (3602s−1) and energy transfer efficiency (65.92%). Important radiative properties have been predicted for emission transitions of Ho3+ ions using intensity parameters derived from measured absorption spectra using standard Judd–Ofelt theory. At lower acceptor ion concentration (0.1mol%), an efficient NIR to visible up-conversion emission has been observed based on two photon absorption process which has found to be reduced significantly at higher Ho3+ concentrations with simultaneous enhancement in 2μm emission. Hence, this newly developed glass codoped with Yb3+/Ho3+ is promising glass for sensitized 2μm emission applications as broad band tunable lasers because of the combination of low phonon energy (707cm−1), high energy transfer efficiency, moderately high emission cross-section (5.33×10−21cm2) and larger effective half-width of the emission band value of 169nm.

Structural changes in the ZnF2–Bi2O3–GeO2 glass system doped with Fe2O3 by spectroscopic and dielectric investigations

Transparent glasses 20ZnF2–40Bi2O3–(40−x)GeO2: xFe2O3; 0≤x≤2.5wt% are prepared by melt quenching technique. The amorphous nature of the glass samples is characterized by X-ray diffraction (XRD) and differential thermal analysis (DTA). Spectroscopic studies like optical absorption, FTIR, Raman and dielectric parameters (ε′, loss(tanδ) and σac over a wide range of frequency and temperature) of these samples have been carried out. Optical absorption data has revealed that the bismuth radicals, observed in pure sample F0, are decreased with increase in concentration of Fe2O3. The optical absorption and ESR studies indicate Fe2+ and Fe3+ ions occupy octahedral positions at higher dopant concentrations of Fe2O3. From FTIR and Raman studies, the coordination of germanium is changed from GeO4 to GeO6 with increase in the concentration of Fe2O3. Dielectric parameters such as dielectric constant ε′, loss tanδ, a.c. conductivity σac are found to increase and activation energy for a.c. conduction is decreased, hence depolymerise the glass network with increase of divalent iron ion concentration; which is also confirmed by band gap energy (Eg). Density of defect energy states N(EF) is explained with quantum mechanical tunnelling (QMT) model.

Effect of composition on Bi2O3–SiO2–GeO2 glass properties

Glasses with composition Bi4(SixGe 1– x )3O12, where x = 0.33, 0.5 and 0.06, were obtained by melting for 30 min and two-step melting. Their characteristic temperatures, densities, refractive indices and microhardness were determined and the composition dependences studied. Glasses in the system Bi 2 O 3 –GeO 2 –SiO 2 are used in optics, electronics, and the telecommunications industry as laser materials when doped with rare-earth elements and as cryogenic charged-particle detectors when reduced in a hydrogen atmosphere. The possibility using these glasses as a basis to obtain glass ceramic materials with scintillation properties is of greatest interest, since many sensitive scintillation elements currently used have a number of substantial drawbacks. For example, NaI and LiI crystals are hygroscopic, which causes instruments to malfunction; CsI is nonhygroscopic but it is unstable under high irradiation doses, which sharply curtails its applicability. ZnS single crystals cannot be used to detect -radiation because of the lose transmission in the visible range. The range of application of single-crystal KI is limited by the presence of 40 K in it. In addition, each material mentioned above requires activating additives, which are required in order for it to scintillate. In this light there is promise in using single crystals with the structure of eulytin (Bi4X3O12, where X = Si, Ge) as the active element, since the centers of emission are bismuth ions, making activators unnecessary. For equal volumes BGO and BSO crystals show higher photon detection efficiency than other scintillation crystals. The undoubted advantages of eulytins are their mechanical properties and nonhygroscopicity. In view of the difficulties arising in growing eulytin crystals, which greatly increase production costs, a step forward is the use of glass ceramic materials based on glasses with equivalent composition. Matrix glasses are produced using well-perfected classic technologies, and glass ceramic materials can be obtained from them by easily accessible methods — heat treatment or laser irradiation. Transparent glass ceramic materials based on glass with the compositions 2Bi 2 O 3 ;3SiO 2 and 2Bi 2 O 3 ;3GeO 2 , containing up to 70% eulytin crystallites and possessing scintillation properties close to those single crystals, have now been obtained. As in the case of single crystals these properties of bismuth-germanate glass ceramics are higher while the radiation resistance is lower than for bismuth-silicate. In turn, bismuth-silicate glass ceramic is characterized by the opposite properties (the scintillation properties are lower but the radiation resistance is higher) [1]. Therefore, combining the useful properties of both materials in a single material is a topical problem. Most works are devoted to studying phase equilibria in the binary systems Bi2O3–GeO2 and Bi2O3–SiO2. The ternary system Bi 2 O 3 –GeO 2 –SiO 2 has been less studied. Glass formation in the indicated system was studied in [2]: the characteristic temperatures were determined, nontransparent glass ceramic materials based on these glasses were obtained, and the composition of the crystallizing phases and the lattice parameters of the crystals formed were determined.

Glass formation and third-order optical nonlinear characteristics of bismuthate glasses within Bi2O3–GeO2–TiO2 pseudo-ternary system

Glass-forming region of Bi2O3–GeO2–TiO2 (BGT) pseudo-ternary system was determined by using melt-quench method. A series of high transparent glass samples were selected and their structural characteristics were investigated by FT-IR and Raman spectra. By employing Z-scan and optical Kerr shutter techniques with femtosecond laser pulses as excitation source, third-order optical nonlinearities (TON) of the BGT glasses as well as the TON response time were investigated at wavelength of 800 nm. The ultrafast nonlinear response and high figure of merit suggest great potentials of BGT glasses in applications of all-optical switching or related optical devices.

Structural and electrical properties of ZnF2–Bi2O3–GeO2 glasses doped with CoO

Abstract Transparent glasses 20ZnF2–40Bi2O3–(40 − x)GeO2:xCoO; 0 ⩽ x ⩽ 1 wt% are prepared by melt quenching technique. The amorphous nature of the samples is characterized by X-ray diffraction (XRD) and differential thermal analysis (DTA). Spectroscopic studies like optical absorption, FTIR, Raman and dielectric parameters (e′, loss tan δ, conductivity σac over a wide range of frequency and temperature as well as dielectric breakdown strength at room temperature) of these samples have been carried out. Optical absorption data has revealed that the bismuth radicals, observed in pure sample C0, are combined with cobalt ions with increase in concentration of CoO. Further, Co2+ and Co3+ ions occupy octahedral positions at larger dopant concentrations of CoO. From FTIR and Raman studies the coordination of germanium is changed from GeO4 to GeO6 with increase in the concentration of CoO. Dielectric parameters such as dielectric constant e′, loss tan δ, a.c. conductivity σac are increased and activation energy for a.c. conduction is decreased and hence opens the glass network with the increase of divalent cobalt ion concentration; which is also confirmed by decrease in glass transition temperature (Tg) and band gap energy (Eg). Density of defect energy states (EF) is explained with quantum mechanical tunneling (QMT) model.

Photoluminescence from germanate glasses containing silicon nanocrystals and erbium ions

We report the first observation of photoluminescence enhancement in Er3+ doped GeO2–Bi2O3 glasses containing silicon nanocrystals (Si-NCs) excited by a laser operating at 980 nm. The growth of ≈200% in the intensity of the Er3+ transition 4S3/2→4I15/2 (545 nm) and of ≈100% for transitions 2H11/2→4I15/2 (525 nm), 4F9/2→4I15/2 (660 nm), and 4I5/2→4I13/2 (1530 nm) was observed in comparison with a reference sample that does not contain Si-NCs. The results open a new road for obtaining efficient Stokes and anti-Stokes emissions in germanate composites doped with rare-earth ions.

Enhanced 1.53-μm and lowered upconversion luminescence in Er3+-doped Ga2O3–GeO2–Bi2O3–Na2O glass by codoping rare earths

Spectroscopic properties and energy transfer (ET) in Ga2O3–GeO2–Bi2O3–Na2O (GGBN, glass doped with Er3+ and rare earths (RE3+; RE3+=Ce3+, Tb3+) have been investigated. Intense 1.53-μm emission with the peak emission cross-section achieved to 7.58×10−21cm2 from Er3+-doped GGBN glass has been obtained upon excitation at 980nm. Effects of RE3+ (RE3+=Ce3+, Tb3+) codoping on the optical properties of Er3+-doped GGBN glass have been investigated and the possible ET mechanisms involved have also been discussed. Significant enhancement of the 1.53μm emission intensity and decrease of upconversion (UC) fluorescence with increasing Ce3+ concentration have been observed. The incorporation of Tb3+ into Er3+-doped GGBN glass could significantly decrease the UC emission intensity, but meanwhile decrease the 1.53μm emission intensity due to the ET from Er3+:4I13/2 to Tb3+:7F2. The results indicate that the incorporation of Ce3+ into Er3+-doped GGBN glass can effectively improve 1.53-μm and lower UC luminescence, which makes GGBN glass more attractive for use in C-band optical fiber amplifiers.

Eulityte glasses – synthesis and characterization

AbstractOxides glasses are suitable for electronic and optoelectronic applications (band gap higher than 3 eV). Eulytite glasses were obtained from Bi4GeO14 sintered powder or mixture oxides powders Bi2O3–GeO2. The powders rapidly heated and melted at 1050 °C for 5 ÷ 10 min was poured on the graphite plates under the glass transition temperature. Structural SEM, XRD and EDX investigations were performed at room temperatures. The frequency dependence of the permittivity and loss (45 Hz ÷ 5 MHz) was investigated on a large temperature range between –140 and +375 °C. The permittivity and loss increase with the temperatures increase and decrease with the frequency increase. An activation energy of 0.88 kcal/mol, comparable to the thermal energy RT = 0.65 kcal/mol, was found for cluster formation on 150 ÷ 200 °C temperature range. The jump of permittivity on the range 275 ÷ 325 °C suggest an incipient glass transition at lower temperatures than 400 °C, as usually is accepted. The permittivity increase, correlated with the dipolar polarization was noticed at higher temperatures. The decrease of permittivity and loss in 10 ÷ 100 kHz frequency range, at the mentioned temperatures, supports this assertion. The estimated relaxation times suggest the big clusters formation. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Structure, electrical, and optical properties of ZnO-substituted PbO for the Er3+/Yb3+ co-doped Bi2O3–GeO2–Na2O glass system

Glasses of the 0.5Er3+/2.5Yb3+ co-doped (40Bi2O3–20GeO2–(30 − x)PbO–xZnO–10Na2O system where x = 0.0, 5, 10, 15, 20, 25, and 30 mol%) have been characterized by FT-IR spectroscopy measurements to obtain information about the influence of ZnO-substituted PbO on the local structure of the glass matrix. The density and the molar volume have been determined. The influences of the ZnO-substituted PbO on the structure of glasses have been discussed. The dc conductivity measured in the temperature range 475–700 K obeys Arrhenius law. The conductivity decreases while the activation energy for conduction increases with increase ZnO content. The optical transmittance and reflectance spectrum of the glasses have been recorded in the wavelength range 400–1100 nm. The values of the optical band gap Eopt for all types of electronic transitions and refractive index have been determined and discussed. The real and imaginary parts e1 and e2 of dielectric constant have been determined.

Synthesis and nonlinear optical properties of TeO 2–Bi 2O 3–GeO 2 glasses

Novel TeO2–Bi2O3–GeO2 glasses possessing nonlinear optical properties were successfully synthesized by the melt-quenching method. Differential thermal analysis, X-ray diffraction, Raman scattering and UV–visible spectroscopy were complementarily applied to study the glass transition and crystallization temperature, structural, thermal and optical properties. The value of the refractive index of the glasses is approximately 2.13. The thermoelectrical poling and subsequent second-harmonic generation results are also reported.

Photoluminescence enhancement by gold nanoparticles in Eu3+ doped GeO2–Bi2O3 glasses

We report large photoluminescence (PL) enhancement in Eu3+-doped GeO2–Bi2O3 glasses containing gold nanoparticles (NPs). Growth of ≈1000% in the PL intensity corresponding to the Eu3+ transition D50→F72, at 614 nm, was observed in comparison with a reference sample that does not contain gold NPs. Other PL bands from 580 to 700 nm are also enhanced. The enhancement of the PL intensity is attributed to the increased local field in the Eu3+ locations due to the presence of the NPs and the energy transfer from the excited NPs to the Eu3+ ions.

The effect of gadolinium addition on the surface structure of Bi2O3–GeO2 glasses and vitroceramics

AbstractHeavy metal oxide glasses and vitroceramics belonging to the Bi2O3–GeO2–Gd2O3 system are investigated. The changes induced by heat treatment in the elemental composition on sample surfaces are related to the local order changes. O 1s and Bi 4f core level X‐ray photoelectron spectra evidence the local order changes caused by gadolinium addition to the Bi2O3–GeO2 matrix and by partial crystallisation of the precursor glass samples. The addition of gadolinium to the Bi2O3–GeO2 glass matrix leads to a reduction of the number of bridging oxygens and a depolymerisation of the glass structure. The number of bridging oxygens increases on heat treatment of the samples. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Frequency upconversion luminescence in Tm3+/Yb3+- and Ho3+/Yb3+-codoped Ga2O3–GeO2–Bi2O3–PbO glasses

This paper reports on frequency upconversion emission properties of Tm3+/Yb3+- and Ho3+/Yb3+-codoped Ga2O3–GeO2–Bi2O3–PbO glass upon excitation of 980 nm laser diode. The dependence of the upconversion emission intensity upon the excitation power has been examined and the involved mechanisms have also been discussed. An intense blue emission at 476 nm and two weak red emissions at 650 and 689 nm have clearly been observed in Tm3+/Yb3+-codoped samples, which are assigned to the 1G4 → 3H6, 1G4 → 3F4 and 3F2,3 → 3H6 transitions of Tm3+ ions. The cube-like dependence of the 476 and 650 nm emissions on the incident pump laser power, indicates three-photon contribute to the blue–red upconversion emissions, respectively. Meanwhile intense green and red emissions peaked at 545 and 660 nm in Ho3+/Yb3+-codoped samples, which are ascribed to the transitions of (5F4, 5S2) → 5I8 and 5F5 → 5I8 transitions of Ho3+, have been confirmed that two photons contribute to these upconversion processes. The observed upconversion emission intensity as function of Yb3+ concentration suggests that the presence of the Yb2O3 plays a major role in enhancing the upconversion emission efficiency.

Tm3+-Doped Gallium?Germanium?Bismuth?Lead Glasses as 1.47 ?m Fiber Amplifier Materials

We report the spectroscopic properties of Tm3+-doped and Tm3+/Ho3+-codoped [Ga2O3–GeO2–Bi2O3–PbO (PbF2)] glasses for S-band optical amplifications. The Judd–Ofelt intensity parameters have been determined based on the measured absorption spectra. It is found that PbF2-modified glasses exhibit a lower Ω2 value, and the addition of PbF2 caused the chemical bond associated with Tm3+ ions to be more ionic. The PbF2-free glasses have large peak emission cross-sections in the range of 2.15–2.18 × 10−21 cm2. Meanwhile, the studied glasses exhibit broad 1.47 μm emission with the full width at half-maximum of 119–126 nm. The results indicate that these glasses are useful host material for broadband S-band fiber amplifiers.

Effects of PbF2 doping on structure and spectroscopic properties of Ga2O3–GeO2–Bi2O3–PbO glasses doped with rare earths

We report an intense room-temperature blue upconversion in Tm3+∕Yb+3-codoped Ga2O3–GeO2–Bi2O3–PbO(PbF2) glasses upon excitation with a convenient 980nm laser diode. Effects of PbF2 doping on the thermal stability, structure, and upconversion properties of Tm3+∕Yb3+-codoped gallate-germanium-bismuth-lead glasses have been investigated. We find that the presence of PbF2 provides two potentials: shortening the ultraviolet cutoff band and decreasing the phonon energy of host glasses. The blue-upconversion intensity has a cubelike dependence on incident pump-laser power, indicating a three-photon process. Energy-transfer process and nonradiative phonon-assisted decay could be responsible for the population of the G41 emitting level of the Tm3+. The results indicate the potential possibility towards the development of an oxide-based blue-upconversion glass-fiber laser.

Tm3+-dopedGa2O3-GeO2-Bi2O3-PbO(PbF2) Glasses for1.47-μm Optical Amplifications

We report the spectroscopic properties and thermal stability ofTm3+-doped Ga2O3–GeO2–Bi2O3–PbO(PbF2)glasses for 1.47-μm optical amplifications. Effects of PbF2doping on the optical properties and thermal stability ofTm3+-doped gallate–germanium–bismuth–lead glass areinvestigated. The measured peak wavelength and full width athalf-maximum of the fluorescence are 1465 nm and ~120 nm, respectively.Significant enhancement of the 1.47-μm emission and the lifetime of a3H4 level with increasing PbF2 doping have beenobserved. The presence of GeO2 provides two potentials ofincreasing the thermal stability and shortening the ultraviolet cutoffband of host glasses.

Optical properties and infrared-to-visible upconversion in Er3+-doped GeO2–Bi2O3 and GeO2–PbO–Bi2O3 glasses

Luminescence properties and upconversion studies of germanate glasses in ternary GeO2–PbO–Bi2O3 and binary GeO2–Bi2O3 systems containing Er2O3 (0.1–1.0wt%) are presented for the first time. The Judd-Ofelt parameters found for these glasses are: Ω2=4.50×10−20cm2, Ω4=1.55×10−20cm2 and Ω6=0.69×10−20cm2 for binary glasses and Ω2=4.44×10−20cm2, Ω4=1.82×10−20cm2 and Ω6=0.39×10−20cm2 for ternary glasses. The refractive index of these glasses is found to be ∼2. The transition 4I13/2→4I15/2 is peaked at ∼1.53μm and shows a radiative lifetime around 5ms. Both systems exhibit similar emission cross-section at 1.53μm around 0.8×10−20cm2. Upconverted green emission at ∼530nm (2H11/2→4I15/2) and ∼550nm (4S3/2→4I15/2) and red emission at ∼668nm (4F9/2→4I15/2) are observed under 980nm cw excitation. Our results suggest that these glasses are promising candidates for applications in photonics.

Mechanochemical Synthesis of Crystalline Compounds in the Bi2O3–GeO2 System

Mechanochemical Synthesis of Crystalline Compounds in the Bi2O3–GeO2 System