Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Glass”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 901 records · Page 50
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

The Global LAnd Surface Satellite (GLASS) evapotranspiration product Version 5.0: Algorithm development and preliminary validation

An accurate estimation of spatially and temporally continuous global terrestrial evapotranspiration (ET) is essential in the assessment of surface energy, water and carbon cycles. The Global LAnd Surface Satellite (GLASS) ET product Version 4.0 (v4.0) based on the Bayesian model averaging (BMA) method was generated to estimate global terrestrial ET. However, certain uncertainty for the GLASS ET product v4.0 limits its application. In this study, we introduced the deep neural networks (DNN) merging framework to improve terrestrial ET estimation for GLASS ET product Version 5.0 (v5.0) generation by integrating five satellite-derived ET products [Moderate Resolution Imaging Spectroradiometer (MODIS) ET product (MOD16), Shuttleworth–Wallace dual-source ET product (SW), Priestley–Taylor-based ET product (PT-JPL), modified satellite-based Priestley–Taylor ET product (MS-PT) and simple hybrid ET product (SIM)]. We compared the performance of DNN method against other merging methods, including GLASS ET algorithm v4.0 (BMA), the gradient boosting regression tree (GBRT) method and the random forest (RF) method, based on 195 global eddy covariance (EC) flux towers covering observations from 2000 through 2015. Validations indicated that the DNN had the highest accuracy among four merging methods across different land cover types, yielding the highest average determination coefficients (R 2 , 0.62), root-mean-squared-error (RMSE, 24.1 W/m 2 ) and Kling–Gupta efficiency (KGE, 0.77) with a of 99% confidence interval. Compared with GLASS ET algorithm v4.0, the DNN improved on the R 2 by approximately 7% (p < 0.01) and the KGE by 10%. Based on the DNN, we then generated 8-day GLASS ET product v5.0 globally with a 1 km spatial resolution from 2001 to 2015 driven by GLASS vegetation and surface net radiation (R n ) datasets and Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA2) datasets. Finally, this global terrestrial ET product provides a valuable dataset for monitoring regional and global water resources and environmental changes.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

A comparative study of the atomic structures of Ge-doped As 4 S 3 and P 4 Se 3 molecular glasses

The structures of pseudo-binary P-Se and As-S glasses with compositions close to the P 4 Se 3 and As 4 S 3 stoichiometry with a few atom %Ge doping were determined using Monte Carlo simulations constrained by density and x-ray scattering measurements. We find that these glasses consist predominantly of P 4 Se 3 and As 4 S 3 molecules. The Ge doping results in some important differences between the two glasses. The P-Se glass displays significantly higher intermolecular connectivity via P-Se-Ge linkages, consistent with the significantly higher glass transition temperature and lower fragility of this liquid compared to its As-S counterpart. We also speculate that a consequence of this difference in the intermolecular connectivity would be to delay any pressure induced conversion from a molecular to a network structure for the Ge doped P-Se glass compared to the Ge-doped As-S glass.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Structures of fluoride containing aluminosilicate low activity nuclear waste glasses: A molecular dynamics simulations study

Fluorine and other halides commonly exist in nuclear waste forms, and due to their volatile nature, halide retention poses an issue affecting waste loading during vitrification. The compositional effect on fluorine incorporation in aluminosilicate glasses is investigated through molecular dynamics simulations. Oxygen and fluorine coordination numbers around glass former and modifier cations, bond angle distributions, and medium range structure features such as Q n distributions, ring size distributions and neutron diffraction structure factors were calculated. It was found that fluorine has higher preference to bond to Ca 2+ than to Na + , both in the melt and the glass, and there is no Si-F bond formation in the glass but they do exist in the melt. Consequently, CaO for Na 2 O substitution can be an effective way to help fluorine retention without significantly changing the glass chemistry. Furthermore, these results thus provide insights on fluorine incorporation in the aluminosilicate nuclear waste glasses and the strategy on how to improve fluorine retention both in the glass and the melt.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Long-term evaluation of solid oxide fuel cell candidate materials in a 3-cell generic short stack fixture, Part II: sealing glass stability, microstructure and interfacial reactions.

A generic solid oxide fuel cell stack test fixture was developed to evaluate candidate materials and processing methods under realistic conditions. Part I of the work addressed the stack fixture, seal system and cell performance of a 3-cell short stack tested at 800oC for 6000h. Commercial NiO-YSZ anode-supported thin YSZ electrolyte cells with LSM cathodes were used for assessment and were tested in constant current mode with dilute (~50% H2) fuel versus air. Part II of the work examined the sealing glass stability, microstructure development, interfacial reactions, and volatility issues. Part III of the work investigated the stability of Ce-(Mn,Co) spinel coating, AISI441 metallic interconnect, alumina coating, and cell degradation. After 6000h of testing, the refractory sealing glass YSO77 (Ba-Sr-Y-B-Si) showed desirable chemical compatibility with YSZ electrolyte in that no discernable interfacial reaction was identified, consistent with thermodynamic calculations. In addition, no glass penetration into the thin electrolyte was observed. At the aluminized AISI441 interface, the protective alumina coating appeared to be corroded by the sealing glass. Air side interactions appeared to be more severe than fuel side interactions. Metal species such as Cr, Mn, and Fe were detected in the glass, but were limited to the vicinity of the interface. No alkaline earth chromates were found at the air side. Volatility was also studied in a similar glass and weight loss in a wet reducing environment was determined. Using the steady-state volatility data, the life time (40,000h) weight loss of refractory sealing glass YSO77 was estimated to be less than 0.1 wt%.

sealing glass, AISI441, aluminization, (Mn,Co)-spi↗
DOE OSTI2011

Thermally stimulated crystallization of (20-x)LiO{sub 2}-80TeO{sub 2}-xWO{sub 3} glass system

Tellurite glasses of the (20-x)LiO{sub 2}-80TeO{sub 2}-xWO{sub 3} system were synthesized (x=0, 5, and 10) and annealed at different temperatures, and the crystallization kinetics was studied using XRD, FTIR spectroscopy, and DSC techniques. XRD data evidenced the amorphous state of as-quenched samples, while thermally treated samples showed the growth of crystalline phases. FTIR spectroscopy was used to observe the evolution of the vibrational mode assigned to the TeO{sub 2} phases. The presence of {gamma}-TeO{sub 2}, {alpha}-TeO{sub 2}, and {alpha}-Li{sub 2}Te{sub 2}O{sub 5} crystalline phases was observed for the sample TL, x=0, while only the first and second phases were observed for TLW5 and TLW10 samples, x=5 and 10, respectively, suggesting that WO{sub 3} enters the structure preferentially as glass former, inhibiting the growth of the phase {alpha}-Li{sub 2}Te{sub 2}O{sub 5}. -- Graphical abstract: Typical DSC thermogram for TLW glasses for different heating rates with insert graphic showing as the Tg is evaluated. Display Omitted Highlights: {yields} The crystallization kinetics was studied using XRD, FTIR spectroscopy, and DSC techniques. {yields} The glass transition and maximum crystallization temperatures increase when the WO{sub 3} content in the glass composition was increased. {yields} The observed asymmetry of crystallization peaks suggests an overlapping of distinct crystallization phases ({alpha}- and {gamma}-TeO{sub 2}). {yields} The WO{sub 3} enters the structure as glass former and does not participate in the crystallization of glass.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Photoluminescence and energy transfer in Tb{sup 3+}/Mn{sup 2+} co-doped ZnAl{sub 2}O{sub 4} glass ceramics

We report on Tb{sup 3+} as efficient sensitizer for red photoemission from Mn{sup 2+}-centers in ZnO-B{sub 2}O{sub 3}-Al{sub 2}O{sub 3}-Si{sub 2}O-Na{sub 2}O-SrO glasses and corresponding gahnite glass ceramics. In comparison to singly or co-doped glasses, the glass ceramics exhibit significantly increased emission intensity. Structural considerations, ESR, and dynamic luminescence spectroscopy indicate partial incorporation of Mn{sup 2+} as well as Tb{sup 3+} into the crystalline phase, the former on octahedral Zn{sup 2+}-sites. Interionic distance and charge transfer probability between both species depend on crystallization conditions. This enables control of the energy transfer process and, hence, tunability of the color of photoemission by simultaneous emission from Tb{sup 3+} and Mn{sup 2+} centers. Concentration quenching in Mn{sup 2+}-singly doped materials was found at a critical dopant concentration of about 1.0 mol%. The energy transfer process was studied in detail by dynamic as well as static luminescence spectroscopy. Spectroscopic results suggest the application of the studied materials as single or dual-mode emitting phosphor for luminescent lighting. - Graphical abstract: In the prepared Tb{sup 3+}/Mn{sup 2+} codoped glass ceramics containing gahnite (ZnAl{sub 2}O{sub 4}) nanocrystals, the luminescence color is changed from green light to yellowish-red light with an increase in Mn{sup 2+} concentration due to enhanced energy transfer from Tb{sup 3+} to Mn{sup 2+} ions. This tunability should have potential applications in solid state lighting to produce white light, which can be obtained by appropriately optimizing the ratio of Tb{sup 3+}/Mn{sup 2+} ions under UV(350 nm) excitation. Highlights: > Photoluminescence from Mn{sup 2+} and Tb{sup 3+} singly and co-doped glasses and gahnite glass ceramics was studied. > Occurrence of energy transfer from Tb{sup 3+} to Mn{sup 2+} was confirmed. > Luminescence color tunability is achieved by varying dopant concentration and crystallization parameters.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Synthesis and morphology of Ba{sub 1-x}RE{sub 2x/3}Nb{sub 2}O{sub 6} nanocrystals with tungsten bronze structure in RE{sub 2}O{sub 3}-BaO-Nb{sub 2}O{sub 5}-B{sub 2}O{sub 3} glasses (RE: Sm, Eu, Gd, Dy, Er)

Ba{sub 1-x}RE{sub 2x/3}Nb{sub 2}O{sub 6} nanocrystals with a tetragonal tungsten bronze (TTB) structure are synthesized using a conventional glass crystallization technique in 2.3RE{sub 2}O{sub 3}-27.4BaO-34.3Nb{sub 2}O{sub 5}-36B{sub 2}O{sub 3} (mol%) (RE=Sm, Eu, Gd, Dy, and Er) glasses. One sharp crystallization peak is observed at {approx}670 Degree-Sign C in both powdered and bulk glasses, and the formation of Ba{sub 1-x}RE{sub 2x/3}Nb{sub 2}O{sub 6} nanocrystals with unit cell parameters of a{approx}1.24 nm and c{approx}0.39 nm was confirmed. It is found from high resolution transmission electron microscope observations that the morphology of Ba{sub 1-x}RE{sub 2x/3}Nb{sub 2}O{sub 6} nanocrystals is ellipsoidal. Their average particle size is in the range of 15-60 nm and decreases with decreasing ionic radius of RE{sup 3+} being present in the precursor glasses. The optical transparent crystallized glass (bulk) shows the total photoluminescence (PL) quantum yield of 53% in the visible region of Eu{sup 3+} ions, suggesting a high potential of Ba{sub 1-x}RE{sub 2x/3}Nb{sub 2}O{sub 6} nanocrystals as PL materials. - Graphical abstract: This figure shows a TEM photograph for the heat-treated (667 Degree-Sign C, 3 h) sample of 2.3Dy{sub 2}O{sub 3}-27.4BaO-34.3Nb{sub 2}O{sub 5}-36B{sub 2}O{sub 3}. An ellipsoidal-shaped Ba{sub 1-x}Dy{sub 2x/3}Nb{sub 2}O{sub 6} nanocrystal with diameters of 17 and 28 nm is observed. The ellipsoidal morphology is a common feature in Ba{sub 1-x}RE{sub 2x/3}Nb{sub 2}O{sub 6} nanocrystals synthesized by the crystallization of 2.3RE{sub 2}O{sub 3}-27.4BaO-34.3Nb{sub 2}O{sub 5}-36B{sub 2}O{sub 3} glasses. Highlights: Black-Right-Pointing-Pointer Ba{sub 1-x}RE{sub 2x/3}Nb{sub 2}O{sub 6} nanocrystals with a tetragonal tungsten bronze structure are synthesized. Black-Right-Pointing-Pointer A glass crystallization technique was applied. Black-Right-Pointing-Pointer The morphology of Ba{sub 1-x}RE{sub 2x/3}Nb{sub 2}O{sub 6} nanocrystals is ellipsoidal. Black-Right-Pointing-Pointer The average particle size with 15-60 nm decreases with decreasing ionic radius of RE{sup 3+}. Black-Right-Pointing-Pointer Ba{sub 1-x}RE{sub 2x/3}Nb{sub 2}O{sub 6} nanocrystals have a high potential as photoluminescence materials.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Spin glass behavior in the Dy{sub 3-x}Y{sub x}TaO{sub 7} (0≤x≤1) system

Several x-compositions of the polycrystalline Dy{sub 3−x}Y{sub x}TaO{sub 7} system, crystallizing in the weberite-type structure, were synthesized and structurally characterized using Rietveld refinements based on X-ray diffraction data. In previous magnetic characterization of Dy{sub 3}TaO{sub 7} (x=0), with the same crystal structure, an antiferromagnetic transition at T=2.3 K has been assigned to this compound. On the basis of DC and AC magnetic susceptibilities analyses, we show in this work that all compounds in the range of 0≤x≤1.0 exhibit a spin glass behavior. The nature of the spin glass behavior in Dy{sub 3−x}Y{sub x}TaO{sub 7}, can be attributed to the highly frustrated antiferromagnetic interaction of the Dy{sup 3+} sublattice and to the Dy{sup 3+}–Dy{sup 3+} distorted tetrahedra array in the weberite-type structure of this system. By fitting AC susceptibility data, using dynamical scaling theory equations, we conclude that a cluster spin glass is present in Dy{sub 3−x}Y{sub x}TaO{sub 7} in the low temperature range. Depending on the x-composition, T{sub g}∼2.2–3.2 K. In the range 15–300 K the system obeys a Curie–Weiss magnetic behavior. - Graphical abstract: Weberite-type crystal structure of the Dy{sub 3−x}Y{sub x}TaO{sub 7} compounds. In this structure the magnetic sublattice is formed by Dy{sup 3+} cations in an arrangement of distorted tetrahedra at the second-nearest neighbor site; this arrangement suggests geometric frustration that leads to a spin glass behavior. - Highlights: • Spin glass of Dy{sub 3−x}Y{sub x}TaO{sub 7} is associated to highly frustrated AFM interaction. • Quasi-one-dimensional feature of the crystal structure. • Suggest the existence of a cluster spin glass in Dy{sub 3−x}Y{sub x}TaO{sub 7}. • Dy{sub 3−x}Y{sub x}TaO{sub 7} system (x=0.33, 0.66, and 1.0) also display spin glass behavior.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

Third-order nonlinear optical properties of Bi{sub 2}S{sub 3} nanocrystals doped in sodium borosilicate glass studied with Z-scan technique

Research highlights: {yields} Sol-gel method to realize the synthesis of Bi{sub 2}S{sub 3} nanocrystals doped in the glass. {yields} High dispersion and narrow distribution of Bi{sub 2}S{sub 3} nanocrystals in the glass. {yields}Z-scan technique employed for nonlinear optical properties of the glass. {yields} Observation that an obvious third-order optical nonlinear properties in the glass. -- Abstract: The third-order nonlinear optical properties of Bi{sub 2}S{sub 3} nanocrystals doped in sodium borosilicate glass are measured by Z-scan technique. The microstructures of the glass are characterized by means of X-ray diffraction, transmission electron microscopy, scanning transmission electron microscopy, energy dispersion X-ray spectra, and high-resolution transmission electron microscopy. The results show that the Bi{sub 2}S{sub 3} nanocrystals ranging from 10 to 30 nm are determined to be of the orthorhombic crystalline phase, and the third-order optical nonlinear refractive index {gamma}, absorption coefficient {beta}, and susceptibility {chi}{sup (3)} of the glass are determined to be 2.56 x 10{sup -16} m{sup 2} W{sup -1}, 4.13 x 10{sup -10} mW{sup -1}, and 1.43 x 10{sup -10} esu, respectively.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Photocatalytic properties of TiO{sub 2}-P{sub 2}O{sub 5} glass ceramics

Highlights: Black-Right-Pointing-Pointer Glass ceramics were prepared in the binary system P{sub 2}O{sub 5}-TiO{sub 2}. Black-Right-Pointing-Pointer Main crystalline phases were anatase-type TiO{sub 2} crystals or (TiO){sub 2}P{sub 2}O{sub 7} crystals. Black-Right-Pointing-Pointer The glass ceramics containing the anatase crystals showed photocatalytic activity. -- Abstract: Binary TiO{sub 2}-P{sub 2}O{sub 5} glasses with 69 mol% and 76 mol% TiO{sub 2} were prepared and converted into glass ceramics by heat-treatments. XRD measurements show that the main crystalline phases precipitated in the glass ceramics are anatase-type TiO{sub 2} crystals or (TiO){sub 2}P{sub 2}O{sub 7} crystals, depending on the concentration of titanium constituent. Photocatalytic activities of the glass ceramics were evaluated by the decomposition of methylene blue (MB) and measuring the water contact angle. It is found that the glass ceramics containing anatase crystals exhibit both photocatalytic oxidation activity and highly photo-induced hydrophilicity under UV irradiation with intensity of 1.0 mW/cm{sup 2}.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Microstructure and luminescence of Yb{sup 3+}-doped fluorosilicate glass ceramics

Highlights: Black-Right-Pointing-Pointer Fine nano-SrF{sub 2} lattices were observed in the fluorosilicate glass ceramics. Black-Right-Pointing-Pointer EDXS analysis showed Yb{sup 3+} was enriched into the SrF{sub 2} nanocrystals. Black-Right-Pointing-Pointer That deduced intense cooperative luminescence of the glass ceramics. Black-Right-Pointing-Pointer NIR emissions appeared large bandwidths and long lifetimes simultaneously. Black-Right-Pointing-Pointer Yb{sup 3+} can be an efficient upconversion sensitizer or NIR activator in this host. -- Abstract: Yb{sup 3+}-doped transparent glass ceramics containing cubic SrF{sub 2} nanocrystals were prepared by heat treating the precursor fluorosilicate glass. The precipitated crystals increase in size and the crystallinity decreases with increasing Yb{sup 3+} doping level. With high-resolution transmission electron microscopy and electron diffraction, the nano-sized nature of SrF{sub 2} was clearly observed. Owing to a significant change in the crystal-field effects with Yb{sup 3+} enriching in the SrF{sub 2} phase, the glass ceramics present near infrared emission with large bandwidths and long lifetimes, simultaneously. This indicates the glass ceramics have potential application in the efficient IR lasers pumping by InGaAs diodes. The glass ceramics can also emit blue upconversion luminescence, deriving from Yb{sup 3+} pairs' cooperative luminescence. It suggested that Yb{sup 3+} can be an efficient upconversion sensitizer for other rare earth ions.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Role of WO{sub 3} on DC conductivity and some optical properties of TeO{sub 2} based glasses

Graphical abstract: Display Omitted Highlights: ► TeO{sub 2}–GeO{sub 2}–WO{sub 3} glass system was prepared using melt quenching method. ► DC conductivity, FESEM, EDS and optical absorption studies were carried out. ► Non bridging oxygens (NBOs) are increases with increase of WO{sub 3} content. ► Increase in NBOs is responsible for the increase in the refractive index of glasses. ► Two charge transport mechanisms are coexist in these glasses. -- Abstract: DC electrical conductivity and optical absorption studies have been employed to understand the influence of WO{sub 3} content on the electrical and optical properties of the TeO{sub 2}–GeO{sub 2}–WO{sub 3} glass system. Field emission scanning electron microscope (FESEM), Energy dispersive X-ray spectrometry (EDS) measurements have been used to confirm the glassy nature and the elemental analysis of the glass composition, respectively. DC electrical conductivity of the glasses was studied in the temperature range 423–613 K. From Arrhenius plot, the activation energies (E{sub act}) of all the glasses have been calculated and conduction mechanism has been discussed in terms of structural changes occurred with the addition of WO{sub 3} content. The optical properties such as optical band gap (E{sub opt}), Urbach energy (ΔE), molar refraction (R{sub M}), metallization criterion (M), electronic polarizability of the oxide ion (α{sub O{sup 2}{sup −}}) and refractive index (n) have been determined from optical absorption data and were found to be composition dependent.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Optical properties of transparent glass–ceramics containing lithium–mica nanocrystals: Crystallization effect

Graphical abstract: Optical properties of transparent Li{sub 2}O–MgO–Al{sub 2}O{sub 3}–SiO{sub 2}–F glasses containing lithium–mica nanocrystals are studied and crystallization condition has been evaluated and optimized to produce transparent glass–ceramics. Crystallization temperatures were determined by differential thermal analysis and crystalline phases were identified and quantified by X-ray diffraction. Scanning electron microscopy was used for morphological variations and UV–vis absorption spectroscopy for comparative analysis of transparency. In order to investigate the optical properties of transparent glass–ceramics, optical band gap, Fermi energy level and Urbach energy are calculated. The results of the investigation illustrate that band gap is reduced with increases in crystallization time and temperature. Enhanced orderliness in the arrangement of atoms might be regarded as possible reasons for the above changes. - Highlights: • The optimum temperature and time of crystallization were determined. • Li–mica nanocrystals with size of <30 nm were formed using a two-step heat-treatment. • Optical band gap and Fermi energy of nanocrystalline materials decreased with increasing of crystallization temperature and time. • Urbach band tailing was decreased with increasing of crystallization condition. - Abstract: Optical properties of transparent Li{sub 2}O–MgO–Al{sub 2}O{sub 3}–SiO{sub 2}–F glasses containing lithium–mica nanocrystals were studied. The crystallization condition of these glasses was evaluated and optimized to produce transparent glass–ceramics. Crystallization temperatures were determined by differential thermal analysis and crystalline phases were identified and quantified by X-ray diffraction. Scanning electron microscopy was used to detect morphological changes and UV–vis absorption spectroscopy was used for comparative analysis of transparency. In order to investigate the optical properties of the transparent glass–ceramics, optical band gap, Fermi energy level and Urbach energy were calculated. The results of the investigation illustrate that the band gap is reduced with increases in crystallization time and temperature. Enhanced orderliness in the arrangement of atoms might be regarded as possible reasons for the above changes.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Crystallization, densification and dielectric properties of CaO–MgO–Al{sub 2}O{sub 3}–SiO{sub 2} glass with ZrO{sub 2} as nucleating agent

SEM micrographs for the pure CaO–MgO–Al{sub 2}O{sub 3}–SiO{sub 2} glass sintered at 850–1000 °C (a) 850 °C, (b) 900 °C, (c) 950 °C, (d) 1000 °C. - Highlights: • ZrO{sub 2} effects on the crystallization of LTCC glass system were investigated. • ZrO{sub 2} effects on the dielectric properties of LTCC glass system were investigated. • LTCC with a dielectric constant of 6.65 and a low dielectric loss can be obtained. - Abstract: The zirconium oxide effects on the crystallization and dielectric properties of CaO–MgO–Al{sub 2}O{sub 3}–SiO{sub 2} (CMAS) glass were investigated. The results showed that phyllosiloxide and anorthite crystallites were observed in sequence during sintering. For glass added with 8 wt% ZrO{sub 2}, homogeneously dispersed tetragonal ZrO{sub 2} crystallites were observed at 850 °C. The as-prepared CMAS glass–ceramics exhibited a dielectric constant of about 6–7 and a dielectric loss below 0.005 at 100 MHz. The dielectric properties of CMAS glass with 8 wt% ZrO{sub 2} sintered at 850 °C show a low dielectric constant of 6.65 and a dielectric loss tangent of about 2.5 × 10{sup −3}, which provides a promising candidate for LTCC applications.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Effect of Er{sub 2}O{sub 3} dopant on electrical and optical properties of potassium sodium niobate silicate glass-ceramics

Highlights: • The KNN–SiO{sub 2} doped Er{sub 2}O{sub 3} glass-ceramics was prepared by incorporation method. • High dielectric constant (458.41 at 100 kHz) and low loss (0.0005) could be obtained. • TEM and SEM confirmed the existence of KNN crystals embedded in glass matrix. • The Er{sub 2}O{sub 3} dopant causes insignificant effect on modifying E{sub g} value. - Abstract: In this study, transparent glass-ceramics from potassium sodium niobate (KNN)-silicate glass system doped with erbium oxide (Er{sub 2}O{sub 3}) were successfully prepared by incorporation method. KNN was added in glass batches as heterogeneous nucleating agent. The KNN powder was mixed with SiO{sub 2} and Er{sub 2}O{sub 3} dopant with KNN and Er{sub 2}O{sub 3} content varied between 70–80 and 0.5–1.0 mol%, respectively. Each batch was subsequently melted at 1300 °C for 15 min in a platinum crucible using an electric furnace. The quenched glasses were then subjected to heat treatment at various temperatures for 4 h. XRD results showed that the prepared glass ceramics contained crystals of KNN solid solution. In contrary, dielectric constant (ϵ{sub r}) and dielectric loss (tan δ) were found to increase with increasing heat treatment temperature. Additionally, optical properties such as absorbance and energy band gap have been investigated.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Spectroscopic and laser properties of Er{sup 3+} doped fluoro-phosphate glasses as promising candidates for broadband optical fiber lasers and amplifiers

Highlights: • Erbium doped different fluoro-phosphate glasses are prepared and characterized. • Spectroscopic properties have been determined using Judd–Ofelt and Mc-Cumber theory. • Prominent laser transition Er{sup 3+}:{sup 4}I{sub 13/2} → {sup 4}I{sub 15/2} is observed at 1.53 μm. - Abstract: Different fluoro-phosphate glasses doped with 0.5 mol% Er{sup 3+} doped are prepared by melt quenching method. Both structural and spectroscopic properties have been characterized in order to evaluate their potential as both laser source and amplifier materials. Optical absorption measurements are carried out and analyzed through Judd–Ofelt and Mc-Cumber theories where spectroscopic parameters such as intensity parameters Ω{sub l} (λ = 2,4,6), transition probabilities, radiative lifetimes, stimulated absorption cross-sections and emission cross-sections at 1.5 μm have been evaluated for Er{sup 3+} doped different fluorophosphate glasses. The various luminescence and gain properties are explained from photoluminescence studies. The decay curve analysis have been done for obtaining the decay time constants of Er{sup 3+} excited level {sup 4}I{sub 13/2} in all the fluoro-phosphate glasses. The obtained results of each glass matrix are compared with the equivalent parameters for several other host glasses. These fluoro-phosphate glasses are found to be suitable candidates for laser and amplifier applications.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Compositional investigation of ∼2 μm luminescence of Ho{sup 3+}-doped lead silicate glass

Graphical abstract: Ho{sup 3+}-doped lead silicate glass with lowest maximum phonon energy possesses highest ∼2 μm luminescence intensity. - Highlights: • With increment of lead oxide, maximum phonon energy in lead silicate glass decreased. • ∼2 μm luminescent intensity of Ho{sup 3+} increased with increment of lead oxide. • Lowest lead oxide content glass possesses highest quantum efficiency due to low maximum phonon energy. - Abstract: Lead silicate glass samples with varying lead oxide content were prepared in this study, and their luminescent properties were examined and analyzed. It was found that with increasing lead oxide content, the maximum phonon energies of the glass samples decreased, while their spontaneous transition probabilities first increased and then decreased. The influence of the spontaneous transition rate, A{sub 10}, and the multi-phonon relaxation rate, W{sub 10}, on the sample luminescent properties was analyzed using rate equations. As a result, it was found that with increasing lead oxide content, W{sub 10}/A{sub 10} decreased, while the quantum efficiency increased. Thus, the luminescent intensity at ∼2 μm increased in the glass samples with increased lead oxide content. The high luminescent intensity and long lifetime indicate that silicate glasses containing high levels of lead oxide could potentially be used in ∼2 μm lasers.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Photoluminescence investigations on Sm3+ ions doped borate glasses for tricolor w-LEDs and lasers

Highlights: • Borate glasses with Sm3+ ions were synthesized by melt quenching technique. • Under 402 nm excitation Borate glasses show reddish orange luminescence. • Energy transfer through cross-relaxation leads to fall in decay time of Sm3+ ions. • I-H model confirms energy transfer between Sm3+ ions as dipole-dipole in nature. • 1 mol% Sm3+ ions in these glasses are apt for red photonic device applications. - Abstract: This work describes mainly the optical absorption, photoluminescence (PL) and decay spectral properties of Sm{sup 3+} ions doped borate glasses to understand their possible usage in tricolor w-LEDs and lasers.The XRD spectrum recorded for an un-doped glass confirms glassy nature of the as prepared glass. The Judd-Ofelt (J-O) intensity parameters evaluated from experimental oscillator strengths were used in estimating the various radiative parameters. Under 402 nm excitation, the PL spectra exhibit intense emission at 600 nm for which the decay spectral profiles were recorded.The decay profiles are converting from single exponential to non-exponential with increase in Sm{sup 3+} ion concentration ensuing decrease in experimental lifetimes which may be attributed to the efficient energy transfer through cross-relaxation process. The non-exponential decay curves fitted to I-H model reveals the interaction between the Sm{sup 3+} ions as dipole-dipole in nature. From the evaluated emission cross-sections, quantum efficiency, branching ratios and CIE co-ordinates, it is concluded that 1 mol% Sm{sup 3+} ions in these glasses are aptly suitable to fabricate reddish-orange luminescent devices.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗