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1.
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 E
opt for all types of electronic transitions and refractive index have been determined and discussed. The real and imaginary parts
ε1 and ε2 of dielectric constant have been determined. 相似文献
2.
Yan Wang Jinghong Ma Dong Liang Meimei Zhou Fuxiang Li Ruifeng Li 《Journal of Materials Science》2009,44(24):6736-6740
Super-acid catalyst, SO4 2?/ZrO2–SiO2, with high zirconium loading was synthesized and the nature of the surface acid was investigated by FT-IR of pyridine adsorption. With the increasing ZrO2 content, the Lewis and Brønsted acid sites increased and reached the maximum when Zr/Si (molar ratio) = 1.3. The sample with Zr/Si = 1.3 showed the strongest IR adsorption band in the S=O stretching region (1,300–1,400 cm?1). Pyrosulfate and monosulfate species existed on the surface of the catalysts and the acidic strength could be enhanced by induction effect of their S=O groups. And there were two kinds of Brønsted acid sites on the surface of the catalysts. 相似文献
3.
E. N. Galashov V. V. Atuchin T. A. Gavrilova I. V. Korolkov Y. M. Mandrik A. P. Yelisseyev Zhiguo Xia 《Journal of Materials Science》2017,52(22):13033-13039
Garnet phosphor Y3Al5O12:Ce3+ is prepared in the Y2O3–Al metal–CeO2 ternary system by the solid-state reaction method in the air. For the first time, metal Al is used as a source of aluminum for the reaction instead of traditional oxide Al2O3. It is shown that the chemical reaction can be realized at lower temperatures and without use of special reducing atmosphere. The structural and spectroscopic properties of the prepared powder phosphor are very close to those earlier reported for the Y3Al5O12:Ce3+ single crystal. 相似文献
4.
Herein, we report the results of the in vitro dissolution tests, which were carried out by immersing the selected glass-ceramic samples in artificial saliva (AS) for various time periods of up to 42 days. In our experiments, the SiO(2)-MgO-Al(2)O(3)-K(2)O-B(2)O(3)-F glass ceramics with different crystal morphology and crystal content were used and a comparison is also made with the baseline glass samples (without any crystals). The bioactivity of the samples was probed by measuring the changes in pH, ionic conductivity and ionic concentration of AS following in vitro dissolution experiments. High resistance of the selected glass-ceramic samples against in vitro leaching has been demonstrated by minimal weight loss (<1%) and insignificant density change, even after 6 weeks of dissolution in artificial saliva. While XRD analysis reveals the change in surface texture of the crystalline phase, FT-IR analysis weakly indicated the Ca-P compound formation on the leached surface. The experimental measurements further indicate that the leaching of F(-), Mg(2+) ions from the sample surface commonly causes the change in the surface chemistry. Furthermore, the presence of (Ca, P, O)-rich mineralized deposits on the leached glass-ceramic surface as well as the decrease in Ca(2+) ion concentrations in the leaching solutions (compared to that in the initial AS solution) provide evidences of the moderate bioactive or mild biomineralisation behaviour of investigated glass-ceramics. 相似文献
5.
Hui-Juan Wang Tilman Zscheckel Bo-Tao Li Hui-Xing Lin Christian Bocker Christian Rüssel Lan Luo 《Journal of Materials Science》2017,52(3):1330-1347
Crystallization and microstructure of glasses with the molar compositions 1MgO·1.2Al2O3·2.8SiO2·1.2TiO2·xLa2O3 (x = 0.1 and 0.4) were thermally treated at different temperatures in the range from 950 to 1250 °C and then analyzed by X-ray diffraction and scanning electron microscopy, in combination with energy-dispersive X-ray spectroscopy and electron backscatter diffraction. It was found that the microstructure is first homogeneous with the precipitation of randomly distributed crystals and then indialite domains with embedded perrierite and rutile crystals are formed. For higher temperatures or prolonged times, more domains appear and expand into the bulk of the sample. Finally, the entire sample consists of the indialite domains and the boundaries that are enriched in rutile, perrierite, and magnesium aluminotitanate. Nevertheless, very distinct differences are observed between the samples with different La2O3 concentrations. For the sample with x = 0.4, the domains were detected at lower temperatures, while the quantity and size of the domains increase faster due to the promoted precipitation of indialite. For the sample with x = 0.1, in addition to the domain boundaries, secondary boundaries between the “regions” (assemblages of the domains) are observed in a larger length scale. The average size of the crystalline phases found between the “regions” is larger than that typically observed at the domain boundaries. The sizes of the crystals at the boundaries decrease with higher concentrations of La2O3, and the crystals (especially perrierite) within the domains become larger, resulting in a more homogeneous microstructure. This results in better dielectric properties, i.e., much higher quality factor for the sample with x = 0.4 in comparison to that with x = 0.1 after heat-treatment at 1150 or 1250 °C. 相似文献
6.
Shumian Xu Sha-sha Liu Cong Zhao Tao Han Dachuan Zhu 《Journal of Materials Science: Materials in Electronics》2017,28(14):10061-10066
The Ba2P2O7:Tb3+, R (R?=?Eu2+, Ce3+) phosphors were synthesized by use of a co-precipitation method. Crystal phase, excitation and emission spectra of sample phosphors are analyzed by means of XRD and FL, respectively. The emission spectra of Ba2P2O7:Ce3+, Tb3+ phosphors exhibit four linear peaks attributed to the 5D4?→?7FJ (J?=?6–3) transition of Tb3+ while four broad emission bands are observed in the emission spectra of Ba2P2O7:Eu2+, Tb3+ phosphors. The effects of Eu2+ concentration on the luminescent properties of Ba2P2O7:Tb3+, R (R?=?Eu2+, Ce3+) are studied. Ce3+ affects the luminescent properties of Ba2P2O7:Ce3+, Tb3+ phosphors just as the sensitizer. However, Eu2+ is considered both as the sensitizer and the activator in Ba2P2O7:Eu2+, Tb3+ phosphors. The chromaticity coordinates of Eu2+ and Tb3+ co-doped phosphors gather around the white light field with the CCT approximate to 5000 K, indicating that the luminescent property of Ba2P2O7:Eu2+, Tb3+ phosphors may approach to a desired level needed for white LED application. 相似文献
7.
Cyril Koughia Gokulakrishnan Soundararajan Safa Kasap Trevor Allen Chris Haugen Ray Decorby N. Ohrui Takeshi Aoki C. Fujihashi 《Journal of Materials Science: Materials in Electronics》2009,20(1):19-22
The positions of Stark levels have been determined, using a step-by-step procedure, in the 4I9/2 and 4F3/2 manifolds of Nd3+ ions from absorption and photoluminescence measurements in the 12–293 K temperature range. This data has been used to calculate the emission cross-section for which the maximum value turns out to be ~2.3 × 10?20 cm2. The radiative recombination time, calculated using Judd–Ofelt analysis, of the 4F3/2 manifold is in close vicinity to the experimentally determined times that were measured by the conventional decay of PL after interruption of excitation and by QFRS. Moreover, the peak time defined by QFRS is independent of temperature. Therefore, the dominant relaxation mechanism from the 4F3/2 excited manifold of Nd3+ ions in GaLaS glass is believed to be by radiative emission. 相似文献
8.
Rajendra Kumar Singh A. Srinivasan G. P. Kothiyal 《Journal of materials science. Materials in medicine》2009,20(1):147
Magnetic bioglass ceramics (MBC) are being considered for use as thermoseeds in hyperthermia treatment of cancer. While the bioactivity in MBCs is attributed to the formation of the bone minerals such as crystalline apatite, wollastonite, etc. in a physiological environment, the magnetic property arises from the magnetite [Fe3O4] present in these implant materials. A new set of bioglasses with compositions 41CaO · (52 ? x)SiO2 · 4P2O5 · xFe2O3 · 3Na2O (2 ≤ x ≤ 10 mol% Fe2O3) have been prepared by melt quenching method. The as-quenched glasses were then heat treated at 1050°C for 3 h to obtain the glass-ceramics. The structure and microstructure of the samples were characterized using X-ray diffraction and microscopy techniques. X-ray diffraction data revealed the presence of magnetite in the heat treated samples with x ≥ 2 mol% Fe2O3. Room temperature magnetic property of the heat treated samples was investigated using a Vibrating Sample Magnetometer. Field scans up to 20 kOe revealed that the glass ceramic samples had a high saturation magnetization and low coercivity. Room temperature hysteresis cycles were also recorded at 500 Oe to ascertain the magnetic properties at clinically amenable field strengths. The area under the magnetic hysteresis loop is a measure of the heat generated by the MBC. The coercivity of the samples is another important factor for hyperthermia applications. The area under the loop increases with an increase in Fe2O3 molar concentration and the. coercivity decreases with an increase in Fe2O3 molar concentration The evolution of magnetic properties in these MBCs as a function of Fe2O3 molar concentration is discussed and correlated with the amount of magnetite present in them. 相似文献
9.
Zengzhe Xi Amin Han Pinyang Fang Wei Long Xiaojuan Li Qianqian Bu 《Journal of Materials Science: Materials in Electronics》2016,27(5):4223-4229
Ho3+-modified Pb(Zn1/3Nb2/3)O3–9PbTiO3 (PZN–9PT) single crystals were grown through a flux method. Phase structure and microstructural morphology of the as-grown single crystals were performed by X-ray diffraction analysis and scanning electron microscopy. The refinement of the lattice parameters were obtained by the Rietveld method. The electrical properties of PZN–9PT single crystals were improved significantly by the modification of Ho3+ ions. The rhombohedral–tetragonal phase transition temperature, Curie temperature, coercive field at 15 kV cm?1, and remnant polarization of Ho3+-modified PZN–9PT single crystals were increased by 14, 42 K, 2.4 kV cm?1, and 7.5 μC cm?2, respectively (i.e., 375.45, 448.45 K, 5.9 kV cm?1, and 38.40 μC cm?2, respectively). Furthermore, Lorentz-type law was used to describe the dielectric relaxor behavior of the as-grown single crystals. 相似文献
10.
Subrata Das A. Amarnath Reddy S. Surendra Babu G. Vijaya Prakash 《Journal of Materials Science》2011,46(24):7770-7775
Potassium calcium borate, KCaBO3:Eu3+ phosphors with various Dy3+ concentrations (0–3 wt%) were synthesized by solid state reaction and studied for the first time. Under various UV–violet
excitations, the obtained single monoclinic phased Dy3+–Eu3+ co-doped KCaBO3 polycrystalline phosphors emit a combination of yellow–blue and red–orange wavelength giving intense white light, which can
easily be controlled by varying the concentration of Dy3+. The increase in white light emission with the increase of Dy3+ concentration indicates the efficient energy inter-ion transfer from Dy3+ to Eu3+ ions. Furthermore, the observed emission lifetimes and the intense white light emission are suggestive exploration for the
present phosphor for potential optoelectronic applications such as white light-emitting phosphor for blue LEDs chips. 相似文献
11.
Shaaban M. Salem E. M. Antar A. G. Mostafa S. M. Salem S. A. El-badry 《Journal of Materials Science》2011,46(5):1295-1304
(10Li2O–20GeO2–30ZnO–(40-x)Bi2O3–xFe2O3 where x = 0.0, 3, 6, and 9 mol%) glasses were prepared. A number of studies, viz. density, differential thermal analysis, FT-IR spectra,
DC and AC conductivities, and dielectric properties (constant ε′, loss tan δ, AC conductivity, σ
ac, over a wide range of frequency and temperature) of these glasses were carried out as a function of iron ion concentration.
The analysis of the results indicate that, the density and molar volume decrease with an increasing of iron content indicates
structural changes of the glass matrix. The glass transition temperature T
g and onset of crystallization temperature T
x increase with the variation of concentration of Fe2O3 referred to the growth in the network connectivity in this concentration range, while glass-forming ability parameter ΔT decrease with increase Fe2O3 content, indicates an increasing concentration of iron ions that take part in the network-modifying positions. The FT-IR
spectra evidenced that the main structural units are BiO3, BiO6, ZnO4, GeO4, and GeO6. The structural changes observed by varying the Fe2O3 content in these glasses and evidenced by FTIR investigation suggest that the iron ions play a network modifier role in these
glasses while Bi2O3, GeO2, and ZnO play the role of network formers. The temperature dependence of DC and AC conductivities at different frequencies
was analyzed using Mott’s small polaron hopping model and, the high temperature activation energies have been estimated and
discussed. The dielectric constant and dielectric loss increased with increase in temperature and Fe2O3 content. 相似文献
12.
G. H. Mhlongo O. M. Ntwaeaborwa M. S. Dhlamini H. C. Swart K. T. Hillie 《Journal of Materials Science》2010,45(19):5228-5236
The successful incorporation of ZnO nanoparticles in Pr3+-doped SiO2 using a sol–gel process is reported. SiO2:Pr3+ gels, with or without ZnO nanoparticles, were dried at room temperature and annealed at 600 °C. On the basis of the X-ray
Diffraction (XRD) results, the SiO2 was amorphous regardless of the incorporation of Pr3+ and nanocrystalline ZnO or annealing at 600 °C. The particles were mostly spherical and agglomerated as confirmed by Field
Emission Scanning Electron Microscopy. Thermogravimetric analysis of dried gels performed in an N2 atmosphere indicated that stable phases were formed at ≥900 °C. Absorption bands ascribed to 3H4-3P(J = 0,1,2), 1I6 and 1D2 in the UV–VIS region were observed from SiO2:Pr3+ colloids. The red cathodoluminescent (CL) emission corresponding to the 3P0 → 3H6 transition of Pr3+ was observed at 614 nm from dried and annealed SiO2:Pr3+ powder samples. This emission was increased considerably when ZnO nanoparticles were incorporated. The CL intensity was measured
at an accelerating voltage of 1-5 keV and a fixed beam current of 8.5 μA. The effects of accelerating voltage on the CL intensity
and the CL degradation of SiO2:Pr3+ and ZnO·SiO2:Pr3+ were also investigated using Auger electron spectroscopy coupled with an Ocean Optics S2000 spectrometer. 相似文献
13.
Keisuke Yasuda Toshiyuki Masui Takahiro Miyamoto Nobuhito Imanaka 《Journal of Materials Science》2011,46(11):4046-4052
Catalytic combustion of methane was investigated on Pt and PdO-supported CeO2–ZrO2–Bi2O3/γ-Al2O3 catalysts prepared by a wet impregnation method in the presence of polyvinylpyrrolidone. The catalysts were characterized
by X-ray fluorescence analysis, X-ray powder diffraction, X-ray photoelectron spectra, transmission electron microscopy, and
BET specific surface area measurements. The Pt/CeO2–ZrO2–Bi2O3/γ-Al2O3 and PdO/CeO2–ZrO2–Bi2O3/γ-Al2O3 catalysts were selective for the total oxidation of methane into carbon dioxide and steam, and no by-products such as HCHO,
CO, and H2 were obtained. The catalytic activities of the PdO/CeO2–ZrO2–Bi2O3/γ-Al2O3 catalysts were relatively higher than those of the Pt-supported catalysts, due to the facile re-oxidation of metallic Pd
into PdO based on lattice oxygen supplied from the CeO2–ZrO2–Bi2O3 bulk. A decrease in the calcination temperature during the preparation process was found to be effective in enhancing the
specific surface area of the catalysts, whereby particle agglomeration was inhibited. Optimization of the PdO amount and calcination
temperature enabled complete oxidation of methane at temperatures as low as 320 °C on the 11.6 wt% PdO/CeO2–ZrO2–Bi2O3/γ-Al2O3 catalyst prepared at 400 °C. 相似文献
14.
S. Bindra Narang Shalini Bahel S. Dash 《Journal of Materials Science: Materials in Electronics》2010,21(11):1186-1190
The influences of Bi substitution on microwave dielectric properties of Ba4(La0.5Sm0.5)9.33Ti18O54 solid solutions were investigated. Dielectric ceramics with general formula Ba4(La(0.5−z)Sm0.5Bi
z
)9.33Ti18O54, z = 0.0–0.2 were prepared by conventional solid state route. The structural analysis of all the samples was carried out by
X-ray diffraction and scanning electron microscopy. The dielectric properties were investigated as a function of Bi contents
using open-ended coaxial probe method in the frequency range 0.3–3.0 GHz at room temperature. Dielectric constant varies from
83 to 88 and loss tangent from 2.1 × 10−3 to 5.5 × 10−3 at 3 GHz with temperature coefficient of resonant frequency changing from 106.7 to −8.4 ppm/oC as Bi contents increases from
z = 0.00–0.20. It has been found that dielectric constant and temperature coefficient of resonant frequency improve whereas
loss tangent is adversely affected with increase in Bi substitution. 相似文献
15.
A. N. Georgobiani V. B. Gutan M. A. Kazaryan A. V. Krotov O. Ya. Manashirov Yu. P. Timofeev 《Inorganic Materials》2009,45(10):1166-1170
Ce3+ doping of Y2O2S:Er3+ can be used to suppress the visible anti-Stokes luminescence of the phosphor under excitation in the range 0.90–0.98 μm.
We take advantage of this effect to create a new, efficient “invisible” IR phosphor emitting in the range 1.5–1.6 μm. 相似文献
16.
Mixed-cation salts of the general composition NaM2[NpO4(OH)2]·4H2O, where M = Rb (I, II) and Cs (III), were synthesized and structurally characterized. The compounds differ from each other in the structural organization. The Np central atom in [NpO4(OH)2]3– anions has oxygen surrounding in the form of a tetragonal bipyramid with the O atoms of hydroxide ions in the apical positions. The hydrated Na+ cations have oxygen surrounding in the form of a distorted octahedron. In the structure of I, there are two independent Rb cations with 10- and 12-vertex coordination polyhedra, and in the structures of II and III the framework of large cations is built of 12-vertex Rb and Cs polyhedra. The coordination polyhedra of the Np and Na atoms, sharing a common edge (I, III), or chains of the coordination polyhedra of the Np and Na atoms, sharing common vertices (II), are accommodated in the channels of the frameworks. Hydrogen bonds influence the crystal packing and the geometric characteristics of the [NpO4(OH)2]3– anions. 相似文献
17.
Gadolinium doped bismuth borate glasses containing up to 30 mol% Y2O3 were prepared by fast melt quenching method. The effect of yttrium on the local order in 3B2O3 · Bi2O3 and B2O3 · Bi2O3 glass matrices, particularly on the bismuth sites, was investigated by infrared (IR) spectroscopy and electron paramagnetic
resonance (EPR) of Gd3+ ions. The IR results show that the local structure is more ordered in the glass system with higher bismuth content and the
progressive addition of yttrium increases the local disorder in both bismuth–borate glass matrices. The EPR results indicate
that Gd3+ ions occupy both bismuth and yttrium sites and reflect the same structural disorder like that suggested by IR results. 相似文献
18.
Mixed-cation salts of the composition NaM2[PuO4(OH)2]·4H2O, where M = Rb (I) and Cs (III), and NaRb5[PuO4(OH)2]2·6H2O (II) were synthesized and structurally characterized. The central Pu atom in [PuO4(OH)2]3– anions has oxygen surrounding in the form of a tetragonal bipyramid with oxygen atoms of hydroxide ions in apical positions. The hydrated Na+ cations have oxygen surrounding in the form of a distorted octahedron. In the structure of I, there are two independent Rb+ cations with 10- and 12-vertex coordination polyhedra (CPs), and in the structure of II, three independent Rb+ cations with the 12-, 11-, and 13-vertex CPs. In the structure of III, the Cs+ cation has a 12-vertex CP. Frameworks of large Rb+ or Cs+ cations can be distinguished in the structure. The CPs of the Pu and Na atoms (I, III) sharing a common edge or the isolated CPs of the Pu and Na atoms (II) are incorporated in these frameworks. Hydrogen bonds influence the crystal packing and the geometric characteristics of the [PuO4(OH)2]3– anions. 相似文献
19.
Yu. A. Barbanel’ R. B. Dushin V. V. Kolin V. P. Kotlin L. G. Mashirov S. N. Nekhoroshkov 《Radiochemistry》2007,49(3):237-240
The absorption spectra of the NpO 2 + (5f 2) ion were examined in the region of the 3H 5 ← 3 H 4 magnetic dipole transition (1530–1760 nm) for series of melts with the UO 2 2+ concentration varied in the opposite directions: (1) NaCl-2CsCl eutectic melt with growing additions of the Cs2UO2Cl4 complex salt and (2) Cs2UO2Cl4 melt with growing additions of the NaCl-2CsCl mixture. Measurements of the integrated intensities of the bands belonging to the NpO 2 + ·UO 2 2+ complex and unbound NpO 2 + throughout the UO 2 2+ concentration range examined (up to 4.4 M in neat Cs2UO2Cl4 melt) and processing of the data obtained in terms of the mass action law showed that the formation-decomposition reaction of the cation-cation complex can be described adequately only using the equation of reaction in the form NpO2Cl 4 3? + UO2Cl 4 2? ? {Cl4ONpO?UO2Cl3}4? = Cl? (with the equilibrium constant of 1.3±0.1). Thus, the formation of the cationcation complex should be treated as replacement of chloride ion in the equatorial plane of uranyl(VI) by neptunyl(V), rather than as simple addition of UO 2 2+ to NpO 2 + . The reverse reaction, decomposition of the cation-cation complex, consists essentially in replacement of neptunyl(V) by chloride ion. 相似文献
20.
D. S. Lipatov A. N. Guryanov M. V. Yashkov M. M. Bubnov M. E. Likhachev 《Inorganic Materials》2018,54(3):276-282
An all-vapor phase MCVD process has been proposed for the fabrication of fiber preforms with a Yb2O3–Al2O3–P2O5–SiO2 multicomponent glass core. We have investigated the tubular preform collapse into a rod and demonstrated approaches capable of preventing P2O5 losses in the central part of the core during the collapse process. Preforms with a flat, perfect step-index profile have been fabricated. 相似文献