Tellurite Glass Matrix Research Articles

Preparation and properties of tellurite glass-based CsPb(BrCl)3@glass fluorescent film for a white light emitting diode color converter

Perovskite nanocrystal glass has the advantages of narrow-band emission, easy tuning, and stable structural, physical, and chemical properties, and can be used to mix with other colored materials for white light modulation. The current white light mode widely adopts the packaging method of blue light chip and yellow phosphor, which has the problem of a blue-yellow cavity and low light quality. In this work, the central wavelength of CsPb(BrCl)3 can be adjusted continuously ranging from 463 nm to 486 nm by adjusting the relative ratio of bromine to chlorine in nanocrystals. On the basis of the previous design of YAG:Ce phosphor-in-glass, perovskite nanocrystal glass powder as a color compensator was introduced into the tellurite glass matrix to form a doubly encapsulated system by low-temperature co-sintering. The yellow phosphor and perovskite nanocrystal glass maintain good structural integrity in the glass matrix. By combining the double-package fluorescent material with the blue chip, the continuous adjustment of chromaticity coordinates along the saddle line is realized, and the color-rendering index is also improved to 81.3.

Study of optical, structural and radiation shielding properties of (55 − x)TeO2–20ZnO–25B2O3–xEr2O3 glass matrix

Abstract Erbium doped zinc boro-tellurite (EZBT) glass samples with molar composition of (55 − x)TeO2–20ZnO–25B2O3–xEr2O3 (x = 0.0, 0.5, 1.0, 1.5 and 2.0 mol.%) were prepared by a conventional melt quenching technique. The prepared samples were characterised using X-ray diffraction, Fourier transform infrared spectroscopy and ultraviolet–visible spectroscopy techniques to investigate the structural, optical and dielectric properties. To study the radiation shielding capabilities, the parameters such as mass attenuation coefficient (μ m), half-value layer (HVL), effective atomic number (Z eff) etc., were evaluated using WinXCom software. Judd–Ofelt analysis was carried out to determine the intensity of electronic transitions and other radiative transition parameters within the 4f shell of erbium ions. The μ m values in a range of (108.5–0.03) cm2 g−1 for energy range (0.01–10) MeV were obtained for 2.0 mol.% erbium-doped tellurite glass matrix. The μ m and HVL values were also compared with conventionally used ordinary concrete and specific lead borate glass at certain energies. The detailed investigation of this current EZBT glass matrix is very useful in the specific optical and radiation shielding applications of this EZBT glass.

Visible-infrared optical performance of Er3+-doped fluorotellurite glass via hybrid structural fluctuations

Improving the physicochemical and optical properties of erbium ion-doped fluorotellurite glass is key to addressing the performance bottleneck of current commercial silicon-based fiber amplifiers. In this study, the ZnF2 is used to reduce the hydroxyl content in the tellurite glass matrix, which improved the fluorescence efficiency. Further, the WO3 modifier is introduced to enable the transformation of TeO4→TeO3+δ→TeO3 and the formation of the octahedral [WO6] units and tetrahedral [WO4] units, as demonstrated by Raman spectroscopy and X-ray photoelectron analysis. Finally, Er3+-doped fluorotellurite glass with stable thermal properties is obtained by adjusting the glass topology. Its excellent visible-near-mid-infrared optical properties make it a promising candidate material for infrared fiber amplifiers and gain media for rare-earth-doped solid-state lasers.

Excellent 2.8 μm fluorescence properties of Dy3+ ions by optimizing the structure of tellurite glasses

Optimizing the luminescence performance of Dy3+ ions by regulating the composition and structure of glass is of significant importance for the further development of mid-infrared (MIR) lasers. In this study, a TeO2–Na2O system was selected as the glass matrix owing to its wide glass-forming range for Dy3+ doping, while B2O3, MgO, and ZnO were selected as modifiers to the binary system to improve the thermal and optical properties. MgO was found to improve the crystallization resistance of the tellurite glass matrix, as revealed by differential scanning calorimetry. Raman and x-ray photoelectron spectroscopy results showed that the structure of the matrices became more flexible with the addition of ZnO. More non-bridging oxygen was released, which aids the enhanced 2.8 μm emission of Dy3+ ions. Therefore, these tellurite glasses are suitable laser gain mediums for Dy3+ luminescence, and the structure can be adjusted according to the requirements of specific practical applications in the MIR band.

Broadband absorption mechanism based on quantum dot glass for filtering field.

Traditional filters are faced with the problems of high price and complex preparation process. It is necessary to find a new method or material to make up for these shortcomings. In this Letter, CsPbBr3 nanocrystals with controllable size were prepared in a tellurite glass matrix by a simple and effective heat treatment process. The absorption wavelength of CsPbBr3 quantum dots gradually shifted to red due to the quantum confinement effect. In addition, the intrinsic photoluminescence intensity of CsPbBr3 quantum dots was reduced by Ce4+-doped quantum dot CsPbBr3 glass, which could shield a short wavelength of 200-530 nm. The uniformly distributed quantum dots ensure high transmittance (>80%) of a long wavelength (560-800 nm), demonstrating that the quantum dot glass material has a broad application prospect as a shortwave shielding material.

Investigation on structural, optical, thermal and gamma photon shielding properties of zinc and barium doped fluorotellurite glasses

Fluorotellurite glasses based on zinc and barium fluorides with total dopant concentration limited to 40 mol% in tellurite glass matrix were obtained by melt quenching technique. Explicit effects of both the zinc and barium fluorides on the tellurite glass network were observed from their response to various studies. The tendency of fluorine atoms to break the network was observed from the formation of more non-bridging sites instead of bridging sites from Raman measurements. Formation of these non-bridging fluorine sites instead of non-bridging oxygen led to an increase in the optical band gap of these samples from 3.36 eV to 3.52 eV. The reduction in the glass transition temperature from 316 °C to 299 °C observed with zinc fluoride doping is due to the breakage in the rigid network structure, while the increase from 316 °C to 329 °C with barium fluoride doping is correlated to the effect of size of barium atoms in the network. Radiation shielding properties calculated in terms of parameters like mean free path, mass attenuation coefficient etc., showed that the presence of more heavily doped elements like barium in the glass matrix led them to exhibit better shielding properties which can be utilized as replacement materials for concrete and lead based glasses as efficient shielding materials.

Preparation and luminescent performances of thermally stable red-emitting phosphor-in-glass for high-power lighting

Phosphor-in-glass (PiG) has become as a promising resin-free color converter for high-power light-emitting diodes (LEDs). However, the challenge in luminescent performances of PiG still remain due to the deficiency of red emission spectrum. Herein, a stable red-emitting PiG was prepared for high-power lighting by introducing 3.5MgO·0.5MgF2·GeO2:Mn4+ (MFG:Mn4+) phosphor particles into a tellurite glass matrix. The microstructures and luminescent performances of prepared PiGs were investigated. PiG-based LEDs were fabricated by combining the prepared PiGs and ultraviolet (UV)-LED chips and their optical performances were adjusted by altering phosphor content. Consequently, the introduced phosphor crystals are chemically stable under sintering process and maintain intact in the glass matrix. With the increase of phosphor content, the red emission intensity is increased. Furthermore, the prepared PiG weakens the thermal quenching of MFG:Mn4+ phosphor and exhibits excellent thermal stability under high temperature operation. The results demonstrate that the prepared PiG is a stable and efficient red-emitting converter for high-power lighting.

Tailored white light emission in Eu3+/Dy3+ doped tellurite glass phosphors containing Al3+ ions

Tellurite glass systems modified by addition of aluminum fluoride AlF3 have been successfully synthesized as host matrices for optically active rare earth ions RE3+ (RE3+ = Eu3+, Dy3+). Samples with different Eu3+ to Dy3+ molar ratio have been studied in order to determine possibility of white light emission via UV excitation. Structural investigations confirmed amorphous character of materials whereas spectroscopic studies brought more insight into glass network's nature. FTIR results shown presence of two features related to tellurite glass matrix (in 490–935 cm−1 spectral region) and another one (940-1250 cm−1) due to aluminum addition. Especially, Al-O and Te-O-Al bonds of AlO4 tetrahedrons have been found. AlO4 units are considered as glass formers that improve network's strength and thermal resistivity against devitrification. Based on XPS studies of Al3+ photoelectron band the existence of Al-O and also Al-F bonds have been examined. Moreover, signals originating from Eu3+ and Dy3+ have been found confirming their valence state. Luminescence results revealed possibility of simultaneous UV excitation of Eu3+ and Dy3+ ions. Excitation with λexc = 390 and 393 nm resulted in white light generation starting from warm white to neutral and cool white depending on Eu3+ concentration and used excitation wavelength. Additionally, increase of decay lifetime of Eu3+ induced by Al3+ presence have been revealed based on luminescence decay analysis. Thus, tellurite glass systems modified by AlF3 and doped with Eu3+/Dy3+ may be considered as promising candidates for white light emitting sources.

Effects of GeO2 concentration on the absorption and fluorescence behaviors of Yb3+ in tellurite glasses

Yb3+-doped tellurite glasses exhibited largest absorption and emission cross sections. However, it is more valuable to achieve larger Stark splitting of Yb3+ than improve the absorption and emission cross sections. In this work, we introduced a part of GeO2 into tellurite glass matrix to enlarge the Stark splitting of Yb3+. The effects of GeO2 concentration on the spectroscopic characteristic of Yb3+ were systematically investigated. The stimulated absorption and emission cross sections increased to be 1.62 pm2 and 0.88 pm2 when the GeO2 concentration up to 30 mol%, then decreased with the GeO2 concentration further increased. The Stark splitting of Yb3+ do not change until the GeO2 concentration up to 30 mol%. The NIR fluorescence lifetimes of Yb3+ drastically decreased from 850 μs to 385 μs with the GeO2 concentration increasing, which was due to the increasing multi-phonon relaxation rate and reabsorption. Intense NIR fluorescence were observed when excited by the ultraviolet light, which can be ascribed to the energy transfer from the CTB of Yb3+-O2- couple to Yb3+. The CTB showed a slight blue-shift from 338 to 313 nm with GeO2 concentration increasing, which was ascribed to the size of the cation site would increase.

Magnetically sensitive nanodiamond-doped tellurite glass fibers

Traditional optical fibers are insensitive to magnetic fields, however many applications would benefit from fiber-based magnetometry devices. In this work, we demonstrate a magnetically sensitive optical fiber by doping nanodiamonds containing nitrogen vacancy centers into tellurite glass fibers. The fabrication process provides a robust and isolated sensing platform as the magnetic sensors are fixed in the tellurite glass matrix. Using optically detected magnetic resonance from the doped nanodiamonds, we demonstrate detection of local magnetic fields via side excitation and longitudinal collection. This is a first step towards intrinsically magneto-sensitive fiber devices with future applications in medical magneto-endoscopy and remote mineral exploration sensing.

Microstructure, thermal, optical and dielectric properties of new glass nanocomposites of SrTiO3 nanoparticles/clusters in tellurite glass matrix

New glass nanocomposites (GNCs) of the nominal compositions [(100-x) TeO2–xSrTiO3] with x=5, 10 and 15 (in mol%) were prepared. The glassy phase in the GNCs samples was established by X-ray diffraction (XRD) and Differential thermal analysis (DTA) studies. The SrTiO3 nanoparticles/clusters embedded in tellurite glass matrix for GNCs were identified by transmission electron microscopic (TEM) and confirmed by Fourier transform infrared (FTIR) study. The optical transmission (at x=5) and the electron spin resonance (ESR) studies for the GNCs samples indicated that the presence of Ti3+ ions in tetragonal distorted octahedral sites. The variation of the thermal, density (ρ) and the molar volume (Vm) of the GNCs samples with increasing SrTiO3 were discussed in terms of the structural modifications that take place in the glass matrix. The dielectric properties and ac conductivity of the GNCs samples cannot be explained on the basis of the proportion of Ti3+ ions only.

Influence of lattice modifier on the nonlinear refractive index of tellurite glass

Abstract We studied the influence of different lattice modifiers (Nb 2 O 5 , Bi 2 O 3, or TiO 2 ) on the nonlinear refractive index of a tellurite glass matrix by using the Z-scan technique. Based on the ability of the lattice modifiers to decrease the band-gap energy while simultaneously increasing the linear refractive index of the TeO 2 -based glass, we investigated how these modifiers affect the nonlinear refractive indices. All studied glass presented high nonlinearities, and the addition of lattice modifiers made only a small contribution to increasing magnitude. These results could be explained through the observation of the band-gap energy reduction, which is related to the increase in the non-bridging oxygen content with the addition of the lattice modifier. The increase in the refractive index nonlinearity is explained by the optical basicity and the high electronic polarizability of the modifiers ions.

Role of ion migrations in ultrafast laser written tellurite glass waveguides.

We report on a strong cross migration of ions in a Tellurite (Te) based glass to form waveguides using a high repetition rate femtosecond laser. The tellurite glass matrix was modified using oxides of P, Na and Zn elements of which Te and Na ions play an important role to form waveguides upon laser irradiation. Tellurium was observed to migrate causing a positive index change zone whereas sodium cross migrates to the tellurium deficient zone forming a relatively low index change region. We have used micro-Raman analysis to scan across the waveguide cross-section to understand the state of the glass network and the relation between ion migration and glass densification for waveguiding. We have found that there is an increase in TeO3 units and reduction of TeO4 units in the Te rich zones enabling densification. This work will help guide the new commercial glass manufacturing industries that aim at producing mid-infrared transparent glasses like tellurite, tellurides and chalcogenides for the production of waveguide based devices.

Management of OH absorption in tellurite optical fibers and related supercontinuum generation

We report the fabrication and the characterization of low OH content and low loss tellurite optical fibers. The influence of different methods of glass fabrication on fiber losses has been investigated. The use of the purest commercial raw materials can reduce the losses below 0.1dB/m at 1.55μm. Incorporation of fluoride ions into the tellurite glass matrix makes the optical fibers transparent up to 4μm. A suspended core microstructured fiber has been fabricated and pumped by nanojoule-level femtosecond pulses, thus resulting in more than 2000-nm bandwidth supercontinuum after a few centimeters of propagation.

Preparation of Ag Nanocomposite Tellurite Glass by Solid-State Field-Assisted Diffusion

Ag nanocomposite tellurite glass was successfully prepared by solid-state field-assisted diffusion. The chemical states of Ag, the microstructures of Ag nanoparticles (NPs), and the optical absorption properties were studied for the as-diffused samples. The formation mechanism of Ag NPs in the present tellurite glass is discussed compared with that in soda-lime silicate glass. The results showed that, although the tellurite glass matrix was free of alkali ions, Ag NPs could also be formed using solid-state field-assisted diffusion. This phenomenon is due to an inherently loose network in the present tellurite glass. Optical absorption in the as-diffused TeO2-Nb2O5-BaO glass was strongly affected by the matrix composition and the process parameters. This work provides a promising method to prepare Ag nanocomposite tellurite glass.

Processing and characterization of core–clad tellurite glass preforms and fibers fabricated by rotational casting

We report results on the processing and characterization of tellurite-based glass preforms (core and cladding bulk glasses) and fibers within the TeO 2–Bi 2O 3–ZnO glass system. The core–clad fiber has been drawn from a core–clad preform prepared via rotational casting. Using Cu as a tracer to assess interface quality between the core and clad layers, we show excellent cladding layer thickness uniformity across lengths of up to 40 mm in a 65 mm long perform. No measurable diffusion of Cu between the core and the clad has been observed, within the accuracy of measurement, indicating good stability and interface quality during casting of melted glass. Micro-Raman spectroscopy has been used to identify subtle post-draw structural modification induced in the preform following the fiber drawing. These changes have been attributed to modification to the bulk glass’ thermal history upon drawing and small scale molecular orientation of chain units within the tellurite glass matrix produced during the fiber drawing process. The resulting fiber was found to have an index step of (0.009 ± 0.002) between the fiber core and clad composition at 632 nm and propagation losses of (3.2 ± 0.1) dB/m at 632 nm and (2.1 ± 0.1) dB/m at 1.5 μm. The primary source of loss in the near-IR (NIR) is associated with residual hydroxyl (OH −) groups in the bulk preform which remain in the glass fiber.

Second Harmonic Generation in BaTiO3 Film Crystallized on Tellurite Glass Surface

Transparent glass-ceramics containing ferroelectric crystalline phases have been successfully prepared by many investigators [1±10]. Non-linear optical properties and electro-optical properties of those materials can be utilized for optoelectronic devices such as an optical switch, an optical shutter, frequency upconversion, and so forth. Borrelli and Layton [3] determined quadratic electro-optic coef®cients of transparent glass-ceramics containing ferroelectric crystals such as NaNbO3 and LiTaO3. They also revealed that a linear electro-optic effect, i.e., Pockels effect is observed in poled transparent glass-ceramics providing the size of the crystalline phase included is at least 0:2 im in size. Kao et al. [6] prepared transparent glass-ceramics containing â-BaB2O4 crystalline phase and revealed that the resultant materials exhibit second harmonic generation. Ding et al. [7, 8] utilized ultrasonic treatments to prepare transparent glass-ceramics where crystalline thin ®lms of â-BaB2O4 and LiNbO3 are formed on the glass surfaces. These glass-ceramic materials manifested ef®cient optical second harmonic generation. Komatsu et al. [9, 10] reported preparation of transparent tellurite glass-ceramics containing dielectric crystals such as LiNbO3 and BaTiO3. In these glass-ceramics, one can increase the crystallite size while keeping the material transparent to visible light, because the refractive index of the tellurite glass matrix is close to those of LiNbO3 and BaTiO3 crystals. Recently, we reported second harmonic generation in transparent tellurite glass-ceramic material where BaTiO3 crystalline phase is precipitated [11]. However, the origin of the second harmonic generation in this glass-ceramic still remains unclear. In the present investigation, we further examine this transparent glass-ceramic to characterize the BaTiO3 phase and to clarify the origin of second harmonic generation. Glass was prepared using reagent-grade BaCO3, TiO2 and TeO2 as starting materials. The raw materials were weighed to make 15BaO 15TiO2:70TeO2 (in mol %) composition, and mixed thoroughly. The mixture was melted in a platinum crucible at 1000 8C for 40 min in air. The melt was poured onto a stainless steel plate and cooled in air. The as-prepared glass was annealed for 30 min at around the glass transition temperature determined by means of differential thermal analysis (DTA). The annealed glass was cut into a plate of about 7 mm 3 7 mm 3 1 mm, and both sides were polished with CeO2 powders. The resultant glass specimens were heat-treated at elevated temperatures to fabricate glass-ceramics. X-ray diffraction analysis with CuKa radiation (Rigaku, RAD-C) was carried out to ascertain that the as-prepared specimen was amorphous and to identify crystalline phases in the heattreated specimens. The second harmonic intensity was measured at room temperature using the Maker fringe method [12]. The fundamental wave of a pulsed Nd:YAG laser (Spectra-Physics, GCR-11) with a wavelength of 1064 nm was used as incident light. The situation of polarization was p-excitation and p-detection. The second harmonic wave generated from the specimen was detected using a monochromator (SPEX, 270M) equipped with a photomultiplier (SPEX, 1424M). The intensity of the second harmonic wave was determined using a digital oscilloscope (Hewlett Packard, 54522A). Details of the measurements of optical second harmonic intensity were described elsewhere [13]. Fig. 1 shows X-ray diffraction patterns of the pulverized glass-ceramic specimen (lower ®gure) and the surface state of the bulk glass-ceramic specimen (upper ®gure) heat-treated at 420 8C for 5 h. These two patterns are evidently different from each other. The diffraction line at around 2e ˆ 31:48 in the lower diffraction pattern is attributable to BaTiO3.