Addition Of GeO2 Research Articles

Visible and near infrared photoluminescence of Pr3+ doped oxy-chalcohalide glasses

We observe the seldom reported near infrared (NIR) emissions at 870nm (FWHM=53nm) and 1037nm (FWHM=67nm) which are in the spectral response region of crystalline silicon photovoltaic solar cells. The emissions are much enhanced with the addition of GeO2, and the possible mechanisms for the photoluminescence spectra evolution are discussed. The decay curves are monitored at both the visible and NIR emissions of Pr3+ doped glasses and lifetimes are calculated using a second-order exponential decay model. Raman spectra are used to characterize some interesting structural evolutions which are responsible for the GeO2 induced luminescence property changes.

Properties of the GeS2–Ga2S3–CsCl–GeO2 oxy-chalcohalide glasses

In the present paper, the effects of GeO2 on properties of GeS2–Ga2S3–CsCl chalcohalide glasses are presented. The absorption spectra, density, microhardness, DSC and the chemical durability are measured. Results show that the addition of GeO2 remarkably improves the physical and chemical properties of the chalcohalide glass while the visible transmission spectrum is influenced little. The oxy-chalcohalide glass was also used as matrix for doping Tm3+ (0.1mol%) which shows the similar NIR luminescence spectrum as the GeS2–Ga2S3–CsCl chalcohalide counterpart. Some interesting structural evolutions are characterized by Raman spectra. The possible mechanism corresponding to the improved properties is discussed.

Synthesis and characterization of BaTi1−xSnxO3–0.5 mol%GeO2

Microcrystalline BaTi1−xSnxO3–0.5mol%GeO2x=0, 0.1, 0.3, 0.5 (BTSx–0.5Ge) and BaTiO3 (BT) ceramics (1–0.5μm) were prepared by a conventional solid-state reaction method. The crystalline structure of the samples was examined using XRD, the microstructure was analyzed by means of electron microscope and the density was measured by the Archimede’s method. The sintered ceramic disks have a tetragonal symmetry for BT, pseudo cubic for BTS1–0.5Ge and cubic symmetry for the other studied materials, with a gradual increase of unit cell dimensions. Small addition of GeO2 can improve the density of BT ceramics: 97.9% for BT–0.5Ge, and 96.21% for pure BT. The highest degree of densification in the case of tin doping is achieved for BTS1–0.5Ge (96.93%). The formation of a liquid phase can lead to an anomalous grain growth, and in the case of BT–0.5Ge the grains are completely surrounded by a frozen eutectic melt. For the dielectric constant, while increasing the Sn concentration, the TC gradually shifts towards lower temperatures, and the peak of this transition becomes broader. The lowering of TC is mostly due to the concentration of tin ions and in a much delicate way to Ge ions. Anomalies are noticed for the orthorhombic transition, where the permittivity is higher than the same transition of the matrix (BT), with a shift towards higher temperatures. The BTS3–0.5Ge and BTS5–0.5Ge are the most stable compositions in terms of dielectric behavior, since in the temperature range 200–400K, ε′r is almost constant. Therefore, these compositions can be used for devices that operate over a wide range of temperatures and frequencies.

Effects of GeO2 addition on physical and electrical properties of BaFe0.5Nb0.5O3 ceramic

This paper presents the effect of GeO2 glass former on the physical and electrical properties of BaFe0.5Nb0.5O3 (BFN) perovskite ceramics. The BFN powder was prepared by a conventional mixed-oxide method and the GeO2 contents, ranging from 1 to 5wt.%, were subsequently added to the calcined BFN powder. The mixtures were pressed and sintered to form dense ceramics. We showed that, with the addition of GeO2, the maximum density was achieved at lower sintering temperature, approximately 200–225°C lower than those required by the pure BFN ceramic. However, the densities of these GeO2 doped BFN ceramics were slightly lower than those of pure BFN due to the occurrence of pores. We also found that the addition of GeO2 reduces the dielectric loss at room temperature from 4.29 to 0.39–0.79 but the dielectric constant at room temperature decreased with the increased GeO2 concentrations. With small amount of added GeO2, ferroelectric property of BFN ceramics was also obtained, as confirmed by their hysteresis loops.

Spontaneous Scrolling of Kaolinite Nanosheets into Halloysite Nanotubes in an Aqueous Suspension in the Presence of GeO2

Despite the natural occurrence of aluminosilicate nanotubes as mineral halloysite, suitable hydrothermal methods for their preparation are still undeveloped due to their lower thermodynamic stability under hydrothermal conditions. The effect of addition of GeO2 to the reaction mixture of SiO2 and Al(OH)3 on the distribution of the morphologies of nanostructured aluminosilicates obtained under hydrothermal treatment at pH 2 and 220 °C has been systematically studied. It was found that the formation of multilayered nanotubes of halloysite (Al2Si2O5(OH)4) occurs at 0.2 Ge/(Si + Ge) molar fraction after 7 days of hydrothermal treatment. The as-obtained halloysite nanotubes are characterized by a high degree of crystallinity, a multilayered (25–40 layers) wall structure, and a typical inner diameter of 5–15 nm. A further increase in Ge/(Si + Ge) molar fraction to 0.5 results in precipitation of single-walled nanotubes analogous to germanium-containing imogolite (Al2SixGe1–xO3(OH)4, x ≈ 0.65) characterized with an average inner diameter of 0.9–1.2 nm. At a lower molar ratio (0.05, 0.1), partially curved, multilayer nanosheets of kaolinite are produced. The complete analysis of structure and morphology of all products was performed using TEM, EDX, SAED, FTIR, and nitrogen adsorption. The mechanism governing the precipitation of Al2Si2O5(OH)4 nanotubes in the presence of Ge(IV) is discussed.

Efficiency Improvement of Organic Solar Cells by Tuning Hole Transport Layer with Germanium Oxide

Improving optical property is critical for optimizing the power conversion efficiency of organic solar cells. In the present research, we show that modification of poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) layer with GeO2 leads to 15% improvement of power conversion efficiency in a polymer solar cells through enhancement of short circuit currents. Modified PEDOT:PSS layer with optimized concentration of GeO2 assists active layer absorbing much light by playing a role of optical spacer. Using AFM and grazing incidence X-ray diffraction (GIXD) data, we also present the evidence that an addition of GeO2 does not affect crystallinity of active layer.

Microstructure and Electrical Properties of BaFe0.5Nb0.5O3 Doped with GeO2 (1–5 wt.%)

In this work, the effects of GeO2 dopant on the electrical properties of BaFe0.5Nb0.5O3 (BFN) perovskite ceramics were investigated. The BFN powder was prepared by a conventional mixed-oxide method using stoichiometric amounts of BaCO3, Fe2O3 and Nb2O5. Afterward the GeO2 contents, ranging from 1 to 5 wt.%, were added to the calcined BFN powder and mixed via vibro-milling method. The mixtures were pressed and sintered at 1125–1150°C for 4 h to form dense ceramics. We showed that the addition of GeO2 caused a reduction of grain size and formation of secondary phases: Ba3Fe2Ge4O14 and BaGeO3. The maximum densities of these BFN doped with GeO2 ceramics were slightly lower than those of the pure BFN due to the occurrence of pores. We also found that the GeO2 doping could improve the dielectric properties of these ceramics at room temperature (25°C). The 1 wt.% GeO2 doped sample exhibited higher dielectric constant of about 1800 and lower dielectric loss of 0.45 comparing to that of pure BFN. However, the dielectric constant values of these ceramics at high temperature (>25°C) were decreased significantly with the increase of GeO2 concentration. In addition, the GeO2 additive gave a weak ferroelectric behavior, leading to change in the pyroelectric coefficient and spontaneous polarization of the GeO2 doped BFN ceramics.

Mixed Si/Ge Apatite-Type Phase Produced by Mechanical Alloying

The aim of the present work is to study the influence of the partial substitution of Si by Ge on the formation of the apatite-type La9.33Si2Ge4O26 phase by mechanical alloying and subsequent annealing. Powders of La2O3, GeO2 and SiO2 were dry milled in a planetary ball milling at increasing rotation speeds of 150, 250 and 350 rpm and milling times up to 50 h. The resulting mixtures were subsequently annealed at increasing temperatures up to 1100 °C. Single phase apatite-like La9.33Si2Ge4O26 was obtained during mechanical alloying at high rotation speed. The higher the rotation speed the lower was the time required for the lanthanum germanosilicate phase formation. For the samples in which complete reaction between initial phases did not occur during milling, La9.33Si2Ge4O26 was always obtained during the annealing process. The more severe was the mechanical alloying process the lower was the annealing temperature required for the apatite phase formation. The formation of apatite phase during mechanical alloying did not provoke significant changes in densification behavior of the milled samples. The addition of GeO2 as raw material promotes a faster formation of the apatite phase as compared to the results obtained using only La2O3 and SiO2.

Effect of GeO2 additive on fluorescence intensity enhancement in bismuth-doped silica glass

We observed the enhancement of fluorescence intensity due to the addition of GeO2 in bismuth-doped silica glass (BiSG), which has a peculiar fluorescence at 1.25 μm with a full width at half-maximum of 300 nm. Experimental results revealed that the fluorescence intensity from BiSG with 5.0 mol% GeO2 increased remarkably to be 26.3 times greater than that without GeO2 additive for the same Bi2O3 concentration (0.1 mol%). Furthermore, the enhanced sample showed almost the same intensity as BiSG without GeO2 for 1.0 mol% Bi2O3. These results demonstrate that GeO2 additive effectively promotes the generation of peculiar luminescent centers.

Addition of GeO2to Reduce the Viscosity of Parent Glasses for Low-Expansion, Transparent Glass?Ceramics Containing High-Quartz Solid Solutions

Parent glasses for fabricating glass–ceramics with nanometer-sized crystals usually have high viscosities, resulting in high processing temperatures. In this study, GeO2 was added to a transparent, near-zero thermal-expansion Li2O–Al2O3–SiO2 glass–ceramic to reduce the viscosity of the parent glass. The effects of this compositional modification on the viscosity and crystal-nucleation rate of the parent glasses, and on the crystal size, thermal expansion, and optical transparency of the resulting glass–ceramics were investigated. It was found that addition of GeO2 was useful in reducing the glass viscosity. Owing to the reduced nucleating rate with the increase in the GeO2 content, the nucleating times required for reaching the smallest crystal size, the lowest coefficient of thermal expansion, and the highest transparency were all increased. With increasing GeO2 content, the lowest coefficient of thermal expansion that can be reached for glass–ceramics increased (0.14–2.9 × 10−6 K−1). The highest transparency of the GeO2-containing glass–ceramics is almost as good as that of the GeO2-free glass–ceramic and is almost independent of GeO2 content when the crystal size is smaller than about 65 nm.

980 nm laser-diode-excited intense blue upconversion in Tm3+∕Yb3+-codoped gallate–bismuth–lead glasses

Intense blue-upconversion in Tm3+∕Yb3+-codoped gallate–bismuth–lead glasses has been achieved under an excitation from a commercially available 980nm laser diode. Energy transfer processes and excited-state absorption account for the population of the G41 emitting level of the Tm3+. Although the addition of GeO2 has enhanced the glass thermal stability, the phonon mode associated with vibration of GeO2 has almost no influence on the blue-upconversion intensity and the radiative lifetime of H43 level. The dependence of the phonon energy of the host on contributions from multiphonon decay on the fluorescence has been discussed. Significant enhancement of the blue-upconversion has also been observed in gallate–bismuth–lead glasses with the incorporation of PbF2 content.

Quantitative Identification of Phonon Modes Controlling the Multiphonon Relaxation in Heavy‐Metal Oxide Glasses

The phonon mode(s) controlling the multiphonon relaxation (MPR) in PbO–Bi2O3–Ga2O3 glass was analyzed, and the effect of GeO2 addition on the MPR process was investigated. MPR rates were obtained from the lifetimes of the Tm3+:3H4 level in glasses over the temperature range 20–280 K. In PbO–Bi2O3–Ga2O3 glass, phonons from the bending vibration between GaO4 tetrahedra (∼550 cm−1) controlled the MPR process. On the addition of GeO2, the phonon mode at ∼770 cm−1 due to the stretching vibration of GeO4 tetrahedra started to affect the MPR process. Phonon modes controlling the MPR process in PbO–Bi2O3–Ga2O3–GeO2 glass were both 550 cm−1 and 770 cm−1.

Thermal analysis and optical transition of Yb3+, Er3+ co-doped lead–germanium–tellurite glasses

In this article, we present a study of a new glass system: lead–germanium–tellurite glasses in the form of 0.05K2O–0.1ZnO–0.1BaO–0.2PbO–xGeO2–(0.55 - x)TeO2 with x = 0.1, 0.2, 0.3, 0.4, 0.5, and 0.55. Differential temperature analysis of this glass system shows that increasing GeO2 content raises the glass transition temperature (Tg) and suppresses the crystallization tendency in a large temperature range from Tg to the glass melting temperature. The maximum vibrational frequency is intermediate between germanate and fluoride glasses, in the range of 750 cm−1 to 820 cm−1. Subsequently, Optical absorption, photoluminescence, and upconversion fluorescence were measured for Yb3+, Er3+ co-doped lead–tellurium–germanate glasses. It was found that the full width at half-maximum of the fluorescence spectrum at 1534 nm decreases and the measured radiative lifetime increases with the replacement of TeO2 by GeO2. Excitation at 976 nm into the glass system leads to an intense green emission and a relatively weak red emission. With the addition of GeO2, the increase of red fluorescence and the decrease of green emission in intensity are due to the increase of nonradiative transition rates between the 4S3/2 and 4F9/2 states of Er3+ ions. The quadratic dependence of the green and red emissions on excitation power indicates that two-photon absorption process occurs in this glass system excited at 976 nm.

Local Bonding States of Titanium and Germanium-doped Tetragonal Zirconia Polycrystal and Their Correlation to High Temperature Ductility

bond with oxygen ions rather than Zr‐O bond. Covalency of TZP is more increased by solution of germanium ions than that of titanium ones. In superplastic deformation of TZP, an addition of GeO2 or TiO2 enhances tensile ductility of TZP. Germanium ion is more effective to improve ductility than titanium. The increment of covalency is in a good agreement with the improvement of elongation to failure in doped TZP. Dopant cations segregate at grain boundaries and form no secondary phase. Assuming that a dopant effect on chemical bonding states in grain boundaries is similar to that in grain interior, segregation of germanium or titanium ion increases covalent bonding strength nearby grain boundaries. Such increasing of covalency is likely to enhance cohesion of grain boundaries. The enhancement of grain boundary cohesion suppresses intergranular failure during tensile deformation at elevated temperatures. This must be the reason why an addition of GeO 2 and TiO2 is effective to improve the high temperature ductility of TZP. Our calculation suggests that the covalency nearby grain boundaries have a critical role in the tensile ductility of TZP.

Determination of equilibrium cations for the KTiOPO4 structure

Single crystals with the structure of KTiOPO4 (KTP) were grown from mixtures containing equal concentrations of KSnOPO4 and KGeOPO4 (i), KTiOPO4 and KGeOPO4 (ii), and KTiOPO4 and KTiOAsO4 (iii), respectively. The comparison of the lattice parameters measured and calculated from Vegard's rule shows that structural stability of KTiOAsO4 is higher in comparison with KTiOPO4. It was found that addition of GeO2 to the KTP containing flux is accompanied by increasing all lattice parameters of KTP that correspond to substitution of As5+ by Ge4+.

Effect of IV Group Element Oxides Addition in SnO<sub>2</sub> Thin Film Gas Sensors

The effects of IV group element (Zr, Ti, Ge, Si) oxides addition on the grain growth of SnO2 thin films at elevated temperature (600-1000°C) were investigated. It was found that addition of 10mol% GeO2 controlled the grain growth of SnO2 effectively without changing the resistivity. Addition of GeO2 decreased the response time for 2-methyl-2-butene by the formation of SnO2 thin films with uniform crystallite size.

Low Temperature Sintering of Ba<sub>2</sub>Ti<sub>9</sub>O<sub>20</sub> Dielectric Ceramics with GeO<sub>2</sub> and B<sub>2</sub>O<sub>3</sub> Additives

Ba2Ti9O20 with GeO2 and B2O3 was synthesized by an ordinary sintering method. Fired densities, dielectric constants and dielectric losses were measured. Ba2Ti9O20 containing B2O3 sintered at lower temperatures and Ba2Ti9O20 containing GeO2 showed more excellent dielectric properties than a single phase of Ba2Ti9O20. However, Ba2Ti9O20 containing GeO2 and B2O3 showed no improvement in the sinterability and dielectric properties by low temperature firing. A two-step addition process, i.e., separate addition of GeO2 and B2O3 before and after the calcination, respectively, was effective in reducing the firing temperature without affecting the dielectric properties. XRD (X-ray diffraction) analysis and SEM (scanning electron microscope) observation were carried out on those samples. The sintering mechanism of Ba2Ti9O20 containing GeO2 and/or B2O3 was proposed and the relationship between the microstructures and dielectric characteristics was discussed.

Preparation and Physical Properties of V2 O5 Aerogels

ABSTRACTMonolithic aerogels and aerogel coatings of hydrated V2O5 containing 0 to 10 mol% GeO2 were prepared from metal alkoxides by hydrolysis and autoclave drying. The bulk aerogels of high porosity, more than 90 %, were obtained. On the other hand, the porosity of the aerogel coatings, about 50 nm in thickness, was about 50 %. The aerogels consisted of micro fibrils, less than 20 nm in diameter. Diffraction peaks of crystalline vanadium oxides were not observed for the as-dried aerogels. Dynamic microhardness of the bulk aerogels was very low, but increased with addition of GeO2· Dc electrical conductivity of the bulk aerogels was lower than that of the bulk xerogels by one order of magnitude, and was isotropie. The aerogels were surface fractal with Ds ≅ 2.7.

Characteristics of pure silica core single-mode fiber

Abstract Single-mode fibers with low attenuation and sufficient reliability are especially important for long-span optical transmission systems. Conventionally, GeO2 has been added to the fiber core region in order to make a refractive index difference between the core and cladding. However, the addition of GeO2 increases Rayleigh scattering loss [1], and deteriorates the chemical stability against hydrogen atmosphere and γ-ray irradiation to bring about an increase in attenuation. [2][3] Therefore, pure silica core single-mode fiber was considered to be an ideal type of fiber, and it was succeeded in being fabricated by utilizing fluorine containing SiO2 cladding.

Raman Spectral Characterization of Pure and Doped Fused Silica Optical Fibers

The utility of Raman spectroscopy as a means of characterizing the properties of pure and doped fused silica has been investigated. Laser-Raman spectra were obtained by forward scattering from solid optical fibers ∼35 to 85 m in length using 514.5 nm excitation with an “image slicer” and a Cary model 81 instrument. Clad and unclad fibers of fused silica and doped fibers having SiO2-GeO2 and SiO2-GeO2-B2O3 cores were examined. Raman spectra were also obtained from bulk samples of glasses, including pure GeO2, pure B2O3, and various compositions of SiO2-GeO2, SiO2-B2O3, and SiO2-GeO2-B2O3. The addition of dopants to fused silica was found to alter the Raman spectrum both by the appearance of new bands, roughly proportional to dopant concentration and not common either to the fused silica or to the dopant alone, and by the marked alteration of other Raman bands, which is indicative of changes in the local intermolecular order. Thus, addition of GeO2 produces new Raman bands at ∼675 and ∼1000 cm−1; and of B2O3, new bands at ∼940 and ∼1350 cm−1. Addition of GeO2 and/or B2O3 weakens the relatively sharp Raman lines near 485 and 600 cm−1 (and a similar but small effect was also noted with increasing OH content). GeO2 and B2O3 together also produce observable narrowing of the broad intense 440 cm−1 Raman contour. These spectral effects are interpreted, respectively, in terms of a decrease in the concentrations of [Formula: see text] and [Formula: see text] defects produced by dopant addition and of a concomitant reordering of the silica structure. Raman spectroscopy thus appears to be a useful optical technique for elucidating the properties of dopants that have been especially chosen for good optical transmission and hence are not easily detectable by absorption measurements.