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1.
Magnetic properties of glass ceramics derived from glasses with composition 41CaO·(52− x)SiO 2·4P 2O 5· xFe 2O 3·3Na 2O (2? x?10 mol% iron oxide (Fe 2O 3)) are reported. Structural investigation revealed the presence of nanocrystalline magnetite phase in the heat-treated samples containing x?2 mol% Fe 2O 3. Magnetic hysteresis cycles of the glass-ceramic samples were obtained with a maximum applied field of ±20 kOe as well as a low field of ±500 Oe, in order to evaluate the potential of these glass ceramics for hyperthermia treatment of cancer. Samples with x>2 mol% of iron oxide exhibited magnetic behavior similar to soft magnetic materials with low coercivity. The evolution of magnetic properties in these samples as a function of iron oxide molar concentration is correlated with the amount and crystallite size of magnetite phase present in them. 相似文献
2.
The characteristics of a BaO–Al 2O 3–B 2O 3–SiO 2–La 2O 3 glass ceramic prepared by spray pyrolysis were studied. Glass powders with spherical shape and amorphous phase were prepared
by complete melting at a preparation temperature of 1 500°C. The mean size and geometric standard deviation of the powders
prepared at the temperature of 1 500°C were 0.6 μm and 1.3. The glass powders had similar composition to that of the spray
solution. The glass transition temperature ( T
g) of the glass powders was 600.3°C. Two crystallization exothermic peaks were observed at 769.3 and 837.8°C. Densification
of the specimen started at a sintering temperature of 600°C, in which Ba 4La 6O(SiO 4) 6 as main crystal structure was observed. Complete densification of the specimen occurred at a sintering temperature of 800°C.
The specimens sintered at temperatures above 800°C had main crystal structure of BaAl 2Si 2O 8. 相似文献
3.
Fourier transform infrared (FT-IR) spectra of xBaO–15Na 2O–(70− x)B 2O 3–15SiO 2 glass system with x=0, 5, 10, 15 and 20 (mol%) has been measured in the spectral range 400–4000 cm −1 at room temperature in order to understand the characteristic frequencies of the chemical bonds and bonding mechanisms, which are susceptible to the structural and spectral changes. The effect of gamma irradiation in the dose range 0.1 kGy–60 kGy on the infrared absorption spectra of these glasses is also reported. The change in the glass structure due to the effect of composition is also discussed. It has been observed that irradiation of the glasses with the gamma rays increases the BO 3 groups and the non bridging oxygens which make the network loose. 相似文献
4.
We study the Zee–Babu two-loop neutrino mass generation model and look for a possible flavor symmetry behind the tri-bimaximal neutrino mixing. We find that there probably exists the μ– τ symmetry in the case of the normal neutrino mass hierarchy, whereas there may not be in the inverted hierarchy case. We also propose a specific model based on a Froggatt–Nielsen-like Z 5 symmetry to naturally accomplish the μ– τ symmetry on the neutrino mass matrix for the normal hierarchy case. 相似文献
5.
TiO 2, RuO 2, and IrO 2 transition metal oxides have many applications in the field of applied electrochemistry. In this work, the mixed solid solutions of TiO 2–RuO 2–IrO 2 coatings have been electrodeposited from aqueous–unaqueous baths. 相似文献
6.
A model-independent analysis of anomalous gauge coupling constants of W
± bosons is presented and the corresponding restrictions on them and on the electromagnetic characteristics of W
± bosons following from the experiments on measuring the e+ e- ? W+ W- ? ( e | / |
m, [`(v)] ) ?( q,[`(q)] ) {e^{+} }{e^{-} } \to {W^{+} }{W^{-} } \to \left( {{{e} \left/ {{\mu, \bar{v}}} \right.}} \right) \oplus \left( {q,\bar{q}} \right) process on the e
+
e
− International Linear Collider are obtained. The method of obtaining the model-independent restrictions on the anomalous gauge
constants is based on the use of the polarization scattering cross sections for different initial and final polarization states. 相似文献
8.
(1− x− y)Bi 0.5Na 0.5TiO 3– xBi 0.5K 0.5TiO 3– yBi 0.5Li 0.5TiO 3 lead-free piezoelectric ceramics have been prepared by an ordinary sintering technique, and their structure, electrical properties,
and temperature characteristics have been studied systematically. The ceramics can be well-sintered at 1050–1150 °C. The increase
in K + concentration decreases the grain-growth rate and promotes the formation of grains with a cubic shape, while the addition
of Li + decreases greatly the sintering temperature and assists in the densification of BNT-based ceramics. The results of XRD diffraction
show that K + and Li + diffuse into the Bi 0.5Na 0.5TiO 3 lattices to form a solid solution with a pure perovskite structure. As x increases from 0.05 to 0.50, the ceramics transform gradually from rhombohedral phase to tetragonal phase and consequently
a morphotropic phase boundary (MPB) is formed at 0.15≤ x≤0.25. The concentration y of Li + has no obvious influence on the crystal structure of the ceramics. Compared with pure Bi 0.5Na 0.5TiO 3, the partial substitution of K + and Li + for Na + lowers greatly the coercive field E
c and increases the remanent polarization P
r of the ceramics. Because of the MPB, lower E
c and large P
r, the piezoelectricity of the ceramics is improved significantly. For the ceramics with the compositions near the MPB ( x=0.15–0.25 and y=0.05–0.10), the piezoelectric properties become optimum: piezoelectric coefficient d
33=147–231 pC/N and planar electromechanical coupling factor k
P=20.2–41.0%. In addition, the ceramics exhibit relaxor characteristic, which probably results from the cation disordering
in the 12-fold coordination sites. The depolarization temperature T
d shows a strong dependence on the concentration x of K + and reaches the lowest values at the MPB. The temperature dependences of the ferroelectric and dielectric properties at high
temperatures may imply that the ceramics may contain both the polar and non-polar regions at temperatures above T
d. 相似文献
9.
xCeO 2–30Bi 2O 3–(70− x) B 2O 3 glasses are synthesized by using the melt quench technique. A number of studies such as XRD, density, molar volume, optical band gap, refractive index and FTIR spectroscopy are employed to characterize the glasses. The band gap decreases from 2.15 to 1.61 eV, refractive index increases from 2.67 to 2.93 and density increases from 4.151 to 4.633 g/cm 3. The decrease in band gap with CeO 2 doping approaches the semiconductor behavior. FTIR spectroscopy reveals that incorporation of CeO 2 into glass network helps to convert the structural units of [BO 3] into [BO 4] and results in Bi–O bond vibration of [BiO 6]. 相似文献
10.
The broadband near-IR emission has been investigated in a series of Er/Tm co-doped Bi 2O 3–SiO 2–Ga 2O 3 (BSG) glasses with 800 nm laser diode as an excitation source. A broadband emission extending from 1350 to 1650 nm with a full width at half maximum (FWHM) around 165 nm is obtained in 0.2 wt% Er 2O 3 and 1.0 wt% Tm 2O 3 co-doped BSG glass. The fluorescence decay curves of glasses are measured and maximum energy transfer efficiency from Er 3+ to Tm 3+ reaches 71% when Tm 3+ concentration is 1.0 wt%. The temperature dependence of the broadband emission spectra in Er 3+–Tm 3+ co-doped BSG glass is also recorded to further understand the energy-transfer processes between Er 3+ and Tm 3+. The present work suggests that Er/Tm co-doped BSG glasses can be a potential candidate for broadband integrated amplifier. 相似文献
11.
Trivalent rare earth ions doped borosulfophosphate glasses are in high demand owing to their several unique attributes that are advantageous for applications in diverse photonic devices. Thus, Sm 3+ ion doped calcium sulfoborophosphate glasses with composition of 25CaSO 4–30B 2O 3–(45? x)P 2O 5– xSm 2O 3 (where x?=?0.1, 0.3, 0.5, 0.7 and 1.0 mol%) were synthesized using melt-quenching technique. X-ray diffraction confirmed the amorphous nature of the prepared glass samples. Differential thermal analyses show transition peaks for melting temperature, glass transition and crystallization temperature. The glass stability is found in the range 91?°C to 116?°C which shows increased stability with addition of Sm 2O 3 concentration. The Fourier transform infrared spectral measurements carried out showed the presence of vibration bands due to PO linkage, BO 3, BO 4, PO 4, POP, OPO, SOB, and BOB unit. Glass density showed increase in value from 2.179 to 2.251?g cm ?3 with increase in Sm 2O 3 concentration. The direct, indirect band gap and Urbach energy calculated were found to be within 4.368–4.184?eV, 3.641–3.488?eV and 0.323–0.282?eV energy ranges, respectively. The absorption spectra revealed ten prominent peaks centered at 365, 400, 471, 941, 1075, 1228, 1375, 1477, 1528 and 1597?nm corresponding to 4D 3/2, 6H 5/2→ 4I 11/2, 6P 3/2, 6F 11/2, 6F 9/2, 6F 7/2, 6F 5/2, 6F 3/2, 6H 15/2 and 6F 1/2 transitions respectively. Photoluminescence spectra monitored at the excitation of 398?nm exhibits four emission bands positioned at 559, 596,643 and 709?nm corresponding to 4G 5/2→ 6H 5/2, 6H 7/2, 6H 9/2 and 6H 11/2 transitions respectively. The nephelauxetic parameters calculated showed good influence on the local environment within the samarium ions site and the state of the SmO bond. The Judd–Ofelt intensity parameters calculated for all glass samples revealed that Ω 6?>?Ω 4?>?Ω 2. The emission cross-section and the branching ratios values obtained for 4G 5/2→ 6H 7/2 transition indicate its suitability for LEDs and solid-state laser application. 相似文献
12.
Glasses in the compositions (Li 2O) 25–(BaO) 25–(P 2O 5) 50−x–(V 2O 5) x (with x=0.5,1.0,1.5,2.0,2.5, and 3.0 mol%) have been prepared by the conventional melt quenching technique. X-ray powder diffractrogram show broad peaks which conforms glassy nature of the sample. Differential scanning calorimetry (DSC) thermograms show characteristic glass transition temperature ( Tg) and it increases with increasing substitution of V 2O 5 for P 2O 5. The measured physical parameters like density, refractive index, ionic concentration and electronic polarizability are found to vary linearly with increasing x. Infrared spectra exhibits few bands, which are attributed to (P=O) AS, (P=O) S, (V=O), (P–O–P) AS,P–O–V, (P–O–P) AS and O–P–O vibrations. The optical absorption spectra of VO 2+ ions in these glasses show three bands and are assigned to the 2B 2→ 2E, 2B 2→ 2B 1 and 2B 2→ 2A 1 transitions. Electron paramagnetic resonance spectra of all the glass samples exhibit resonance signals characteristic of VO 2+ ions. The values of Spin-Hamiltonian parameters indicate that the VO 2+ ions are present in octahedral sites with tetragonal compression and belong to C 4V symmetry. 相似文献
13.
We investigate a strongly singular version of the model of irreversible dynamics proposed by Smilansky and Solomyak in which the interaction responsible for an abrupt change of the spectrum is of type. We determine the spectrum in both the subcritical and supercritical regimes and discuss its character as well as its asymptotic properties of the discrete spectrum in terms of the coupling constant. 相似文献
14.
Shell-core Fe–Sr 0.8La 0.2Fe 11.8Co 0.2O 19 composites are prepared by chemical vapor deposition (CVD) for use as microwave absorbing materials. Scanning electron microscopy and X-ray diffraction analyses show that the CVD method yields Sr 0.8La 0.2Fe 11.8Co 0.2O 19 powders with a uniform coating of Fe. Compared with Sr 0.8La 0.2Fe 11.8Co 0.2O 19, Fe–Sr 0.8La 0.2Fe 11.8Co 0.2O 19 composites have higher electrical conductivity, permittivity, and dielectric loss, which gradually increase with increasing Fe content. When Sr 0.8La 0.2Fe 11.8Co 0.2O 19/Fe=7:3, a reflection loss (RL) exceeding −10 dB is obtained in the frequency range of 10–14 GHz at a coating thickness of 2.0 mm. A minimum RL of −30 dB was found at 8.0 GHz, corresponding to a matching thickness of 2.8 mm. 相似文献
15.
We report the microstructure change of BaSnO 3 (BSO)–YBa 2Cu 3O 7−x (YBCO) thin film system grown on SrTiO 3 single crystal substrates by pulsed laser deposition with using the “surface-modified-target” and “mixture-target” methods. Although it was confirmed that the thick BSO nanorods incorporated to YBCO films act as strong artificial pinning centers, the formation mechanism of the nanorods is still unclear. The purpose of this work is to extend the structural investigation to higher contents of BSO (up to 71 vol.%) in order to enlighten the relationship among interfacial energy, morphology and pinning performance in binary BSO–YBCO films. 相似文献
18.
本文使用静态扩散法结合常规X射线粉末衍射和电子探针技术,在Ag-In-Se体系中发现了Ag yIn 3.33-y/3Se 5新化合物.其结构属于三方晶系,空间群为P3m1,是二维层状结构,单层晶胞由9个原子量子层按照Se1-In1-Se2-In2-Se3-Ag/In3-Se4-In4-Se5顺序排布构成,层间由弱范德瓦耳斯力结合.烧结的块体样品表现出强烈的取向性,在平行压力方向上具有极低的晶格热导率(在873 K为0.15 W·m -1·K -1).这种本征低的晶格热导率主要源于材料的低声速和低频光学支声子与声学支声子强耦合作用.Ag yIn 3.33-y/3Se 5样品表现为n型传导,室温下电导率约为4×10~4S·m -1,Seebeck系数约为-80μV·K -1,样品在宽温度范围内均表现出较好的电传输性能,在450—800 K范围内的功率因子为5μW·cm -1... 相似文献
19.
Cr 2O 3 doped SnO 2–Zn 2SnO 4 composite ceramics were prepared by traditional ceramic processing and the varistor, dielectric properties were investigated. With increasing Cr 2O 3 content, the breakdown electrical field EB increases from 11 to 92 V/mm and the relative dielectric constant εr measured at 1 kHz, 50 °C decreases from 11,028 to 3412, respectively. The barrier height ?B about 0.8–0.84 eV and the decreasing of SnO 2 grain size suggest that the varistor behavior with high εr is originated from SnO 2–SnO 2 or SnO 2–Zn 2SnO 4 grain boundary. In the dielectric spectra lower than 1 kHz, a dielectric peak is presented and depressed with increasing bias voltage. Similarly, at high temperature, the dielectric constant also presents a dielectric peak in the temperature spectra and the peak becomes faint with increasing frequency. The exhibition of the dielectric peak is thought to be attributed to the conduction of grain boundary since it is accompanied by the sharp increase of dielectric loss. In addition, a dielectric relaxation with the activation energy about 0.4–0.5 eV was observed in the temperature range of 20–100 °C. Based on the results, the formation mechanism of Schottky barriers at grain boundaries and the varistor behavior with high dielectric constant are well understood. 相似文献
20.
In the present work, manganite La 0.67Pb 0.33MnO 3 was prepared by the sol–gel method. The difference between metal–insulator transition temperature TMI (217 K) and Curie temperature Tc (342 K) in the sol–gel nanocrystalline manganite is mainly due to the grain boundary effect. The breaking of Mn–O–Mn bonds and strong scattering at the grain boundary cumber the transport. At room temperature 300 K, impedance and resistance increase with increasing frequency of ac currents. The observed dc magnetoresistance in sol–gel La 0.67Pb 0.33MnO 3 is related to the spin-polarized inter-grain tunneling and spin-dependent scattering at grain boundaries. The sol–gel manganite shows the magnetoimpedance characteristics, which are different from those of traditional sintered manganites and metallic giant magnetoimpedance materials. For sol–gel La 0.67Pb 0.33MnO 3 at low frequencies, the impedance experiences a peak under a low longitudinal field. In contrast, at high frequencies the peak phenomenon disappears, and the impedance drops sharply with low fields, which is due to the inter-grain or grain boundary effect. The permeability also sensitively varies with an application of transverse field. The magnetoimpedance effect in sol–gel nanocrystalline manganite is influenced by both field-induced permeability change and dc magnetoresistance. 相似文献
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