共查询到20条相似文献,搜索用时 15 毫秒
1.
Changhyun Jin Hyunsoo Kim Kyungjoon Baek Hyoun Woo Kim Chongmu Lee 《Journal of Materials Science: Materials in Electronics》2010,21(11):1154-1158
TiO2-sheathed Ga2O3 one-dimensional (1D) nanostructures were synthesized by thermal evaporation of GaN powders and then sputter-deposition of
TiO2. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis results indicate that the Ga2O3 cores are of a single crystal nature with a monoclinic structure while the TiO2 shells are amorphous. Photoluminescence (PL) emission is slightly decreased in intensity by TiO2 coating, but it is significantly increased by thermal annealing in an oxygen atmosphere. The emission peak is also shifted
from ~500 to ~550 nm by oxygen annealing. The increase in the green emission is due to the increase in the concentration of
the Ga vacancies in the cores by the inflow of oxygen during oxygen annealing. On the other hand, annealing in a nitrogen
atmosphere leads to a red shift of the emission to ~700 nm originating from nitrogen doping. 相似文献
2.
Kamarajan Thiyagarajan Munisamy Muralidharan Kandasamy Sivakumar 《Journal of Superconductivity and Novel Magnetism》2018,31(1):117-125
A series of reduced graphene oxide (rGO)-WO3 nanocomposites were prepared by hydrothermal method using GO and tungsten complex. The nanocomposites were characterized by powder XRD, Raman spectroscopy, FT-IR spectroscopy, HRTEM, XPS, photoluminescence (PL), and magnetic studies. The structural analysis confirms the hexagonal crystal structure and formation of rGO-WO3 nanocomposites. HRTEM images show rod-like shape WO3 distributed on the wrinkle structure of rGO sheets. XPS results confirm the oxidation state and oxygen vacancies present in the samples. PL spectra of the samples show blue emission and indicate the existence of surface defects and oxygen vacancies. The M–H loop of rGO-WO3 nanocomposites reveal that the co-existence of both ferro and antiferromagnetism at room temperature. The incorporation of rGO sheets notably increase magnetic behavior of composites due to extended C–C bond conducts much stronger coupling between the 5d and 6s orbitals of tungsten and carbon atoms. 相似文献
3.
N. Sai Krishna S. Kaleemulla G. Amarendra N. Madhusudhana Rao C. Krishnamoorthi I. Omkaram D. Sreekantha Reddy 《Journal of Materials Science: Materials in Electronics》2015,26(11):8635-8643
The (In1?xCrx)2O3 powders as well as thin films of x = 0.03, 0.05 and 0.07 were synthesized using a solid state reaction and an electron beam evaporation technique (on glass substrate), respectively. The influence of Cr doping concentration on structural, optical and magnetic properties of the In2O3 samples was systematically studied. The X-ray diffraction results confirmed that all the Cr doped In2O3 samples exist cubic structure of In2O3 without any secondary phases presence. The chemical composition analyses showed that all the Cr doped In2O3 compounds were nearly stoichiometric. The X-ray photoelectron spectroscopy analysis of the Cr doped In2O3 thin films showed an increase of oxygen vacancies with Cr concentration and the existence of Cr as Cr3+ state in the host In2O3 lattice. A small blue shift in the optical band gap was observed in the powder compounds, when the dopant concentration increased from x = 0.03 to x = 0.07. In thin films, the band gap found to increase from 3.63 to 3.74 eV, with an increase of Cr concentration. The magnetic measurements show that the undoped In2O3 bulk powder sample has the diamagnetic property at room temperature. And a trace of paramagnetism was observed in Cr doped In2O3 powders. However (In1?xCrx)2O3 thin films (x = 0.00, 0.03, 0.05 and 0.07) samples shows soft ferromagnetism. The observed ferromagnetism in thin films are attributed to oxygen vacancies created during film prepared in vacuum conditions. The ferromagnetic exchange interactions are established between metal cations via free electrons trapped in oxygen vacancies (F-centers). 相似文献
4.
Jing Wang Yanhe Han Manzhi Feng Jinzhu Chen Xinjun Li Shanqing Zhang 《Journal of Materials Science》2011,46(2):416-421
WO3/TiO2 nanotube array electrode was fabricated by incorporating WO3 with TiO2 nanotube array via a wet impregnation method using ammonium tungstate as the precursor. TiO2 and WO3/TiO2 nanotube arrays were characterized by field emission scanning electron microscopy, X-ray diffraction, and energy dispersive
X-ray analysis. In order to characterize the photoelectrochemical properties of WO3/TiO2 electrode, electrochemical impedance spectroscopy, and steady-state photocurrent (i
ss) measurement at a controlled potential were performed in the supporting electrolyte containing different concentrations of
glucose. The photoelectrochemical characterization results reveal that WO3/TiO2 nanotube array electrode possesses a much higher separation efficiency of the photogenerated electron–hole pairs and could
generate more photoholes on the electrode surface compared with the pure TiO2 nanotube array electrode. The i
ss for glucose oxidation at WO3/TiO2 nanotube array electrode is much higher than that at the pure TiO2 nanotube array electrode. 相似文献
5.
Hemisphere-like F-doped anatase TiO2 has been synthesized by hydrothermal treatment of TiF4 aqueous solution in the presence of starch at 130 °C for 10 h, and then calcined at 450 °C for 2.5 h in air. The as-synthesized
product has been investigated by photocatalytic reaction test and characterized by powder X-ray diffraction (XRD), scanning
electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray photoelectron
spectroscopy (XPS), and UV–Vis diffuse reflectance spectra (DRS). The results showed that fluorine was successfully doped
into the TiO2 hemispheres. The F-doped TiO2 hemispheres showed high visible light activity in degradation of acid orange II, which could be attributed to the creation
of oxygen vacancies and good crystallinity. 相似文献
6.
X. H. Zheng J. Xiao X. Huang D. P. Tang X. L. Liu 《Journal of Materials Science: Materials in Electronics》2011,22(8):1116-1119
The formation behavior of CaCu3Ti4O12 (CCTO) had been investigated via solid state reaction from CaTiO3, CuO and TiO2 powders. In the temperature range from 750 to 1,200 °C, the reaction sequence was traced by XRD, and the microstructure evolution
of calcined powders was also investigated by SEM. CCTO began to form owing to the reaction between CaTiO3, CuO and TiO2 at around 850 °C, and became the major phase at 1,000 °C. Finally, the single phase CCTO was obtained at 1,150 °C. However,
CCTO was decomposed at CaTiO3, CuO and TiO2 when the temperature increased to 1,200 °C. In addition, no other intermediate phases occurred in the synthesized process.
The formation behaviors indicated that CaTiO3 prevented the formation and growth of CCTO. 相似文献
7.
Double perovskite La2NiMnO6 thin films were prepared on Pt/TiO2/SiO2/Si substrates by the pulsed laser deposition process, and the crystal structure and microstructures were investigated. The
temperature and the oxygen pressure played the primary roles dominating the crystallization behavior and the morphology of
La2NiMnO6 thin films. The well crystallized La2NiMnO6 thin films could be obtained at 873 and 923 K under all oxygen pressures investigated here, and the fine morphology was obtained
under the oxygen pressures equal to or higher than 50 and 100 Pa, respectively, while phase constitution was significantly
affected by the oxygen pressure for La2NiMnO6 thin films prepared at 1,023 K where the higher oxygen pressure led to the appearance of some secondary phase. 相似文献
8.
A. I. Stognij N. N. Novitskii O. L. Golikova A. V. Bespalov R. Gieniusz A. Maziewski A. Stupakiewicz M. N. Smirnova V. A. Ketsko 《Inorganic Materials》2017,53(10):1069-1074
Amorphous yttrium iron garnet films ranging in thickness from 100 to 600 nm have been produced on single-crystal silicon substrates by sputtering a polycrystalline target with the composition Y3Fe5O12 (yttrium iron garnet) by a mixture of argon and oxygen ions. Before film growth, AlO x or SiO2 buffer layers up to 0.8 μm in thickness were grown on the Si surface. The heterostructures were crystallized by annealing in air at a temperature of 950°C for 30 min. The properties of the films were studied by magneto-optical techniques, using Kerr effect and ferromagnetic resonance measurements. The Gilbert damping parameter reached 2.8 × 10–3 and the effective planar magnetic anisotropy field was independent of the nature of the buffer layer. This suggests that the thin-film heterostructures obtained in this study are potentially attractive for use in spin-wave semiconductor devices. 相似文献
9.
xBaTiO3 + (1 − x)Ni0.93Co0.02Cu0.05Fe2O4 (x = 0.5, 0.6, 0.7, 0.8) composites with ferroelectric–ferromagnetic characteristics were synthesized by the ceramic sintering
technique. The presence of constituent phases in the composites was confirmed by X-ray diffraction studies. The average grain
size was calculated by using a scanning electron micrograph. The dielectric characteristics were studied in the 100 kHz to
15 MHz. The dielectric constant changed higher with ferroelectric content increasing; and it was constant in this frequency
range. The relation of dielectric constant with temperature was researched at 1, 10, 100 kHz. The Curie temperature would
be higher with frequency increasing. The hysteresis behavior was studied to understand the magnetic properties such as saturation
magnetization (M
s). The composites were a typical soft magnetic character with low coercive force. Both the ferroelectric and ferromagnetic
phases preserve their basic properties in the bulk composite, thus these composites are good candidates as magnetoelectric
materials. 相似文献
10.
Si‐Ming Wu Xiao‐Long Liu Xi‐Liang Lian Ge Tian Christoph Janiak Yue‐Xing Zhang Yi Lu Hao‐Zheng Yu Jie Hu Hao Wei Heng Zhao Gang‐Gang Chang Gustaaf Van Tendeloo Li‐Ying Wang Xiao‐Yu Yang Bao‐Lian Su 《Advanced materials (Deerfield Beach, Fla.)》2018,30(32)
The homojunction of oxygen/metal vacancies and its interfacial n–p effect on the physiochemical properties are rarely reported. Interfacial n–p homojunctions of TiO2 are fabricated by directly decorating interfacial p‐type titanium‐defected TiO2 around n‐type oxygen‐defected TiO2 nanocrystals in amorphous–anatase homogeneous nanostructures. Experimental measurements and theoretical calculations on the cell lattice parameters show that the homojunction of oxygen and titanium vacancies changes the charge density of TiO2; a strong EPR signal caused by oxygen vacancies and an unreported strong titanium vacancies signal of 2D 1H TQ‐SQ MAS NMR are present. Amorphous–anatase TiO2 shows significant performance regarding the photogeneration current, photocatalysis, and energy storage, owing to interfacial n‐type to p‐type conductivity with high charge mobility and less structural confinement of amorphous clusters. A new “homojunction of oxygen and titanium vacancies” concept, characteristics, and mechanism are proposed at an atomic‐/nanoscale to clarify the generation of oxygen vacancies and titanium vacancies as well as the interface electron transfer. 相似文献
11.
The effect of Ca substitution for Sr on the phase, microstructure and microwave dielectric properties of the Sr5−x
Ca
x
Nb4TiO17 composition series was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), an LCR meter, and
vector network analyzer. Below 1450 °C, Sr5−x
Ca
x
Nb4TiO17 (x = 1, 2, 3, or 4) compositions formed single-phase Sr4CaNb4TiO17, Sr3Ca2Nb4TiO17, Sr2Ca3Nb4TiO17, and SrCa4Nb4TiO17 ceramics, respectively. At x = 0 and 5, Sr5Nb4TiO17 and Ca5Nb4TiO17 formed, but along with Sr2Nb2O7 (at x = 0) and CaNbO3 and CaNb2O6 (at x = 5) secondary phases. Above 1450 °C, all the compositions formed two-phase ceramics. At low frequencies, a phase transition
was observed in the composition Sr5Nb4TiO17. The substitution of Ca for Sr enabled processing of highly dense Sr2Ca3Nb4TiO17, with εr ~ 53.4, τf ~ −6.5 ppm/°C and Q
u
× f
o
~ 1166 GHz. Further investigations are required to improve the quality factor of these ceramics for possible microwave applications. 相似文献
12.
We developed a process for preparing SiO2/TiO2 fibers by means of precursor transformation method. After mixing PCS and titanium alkoxide, continuous SiO2/TiO2 fibers were fabricated by the thermal decomposition of titanium-modified PCS (PTC) precursor. The tensile strength and diameter
of SiO2/TiO2 fibers are 2.0 GPa, 13 μm, respectively. Based on X-ray diffraction (XRD), scanning electron microscopy (SEM), and high resolution
transmission electron microscopy (HRTEM) measurements, the microstructure of the SiO2/TiO2 fibers is described as anatase–TiO2 nanocrystallites with the mean size of ~10 nm embedded in an amorphous silica continuous phase. 相似文献
13.
W. F. Qin J. Zhu J. Xiong J. L. Tang W. J. Jie X. H. Wei Y. Zhang Y. R. Li 《Journal of Materials Science: Materials in Electronics》2007,18(12):1217-1220
Ba0.6Sr0.4TiO3 (BST) and 1.5 at% Y-doped Ba0.6Sr0.4TiO3 (Y-BST) thin films have been deposited on single-crystal (100) oriented LaAlO3 substrates using pulsed-laser deposition technique (PLD), respectively. X-ray diffraction (XRD) scanning revealed that the
two kinds of films could be epitaxially grown in pure single-oriented perovskite phases, but Y-BST thin films showed an enhanced
crystallization effect. The dielectric properties of the pure and Y-BST thin films were measured at 10 kHz and 300 K with
a parallel-plate capacitor configuration. The results revealed that the addition of Y as an acceptor doping is very effective
to increase dielectric tunability, and to reduce leakage current of BST thin films. The figure-of-merit (FOM) factor value
increases from 17.32 for BST to 25.84 for Y-BST under an applied electric field of 300 kV/cm. The leakage current density
of the BST thin films at a negative bias field of 300 kV/cm decreases from 2.45 × 10−4 A/cm2 to 1.55 × 10−6 A/cm2 by Y doping. The obtained results indicated that the Y-doped BST thin film is a promising candidate material for tunable
microwave devices. 相似文献
14.
We have studied the structure, electric resistance, and magnetoresistance of 30-nm-thick (110)La0.67Ca0.33MnO3 (LCMO) films grown by laser deposition on (001)-oriented LaAlO3 substrates. The unit cell parameters a and b (along the [100] and [010]LCMO axes, respectively) of these manganite films are significantly (by ∼1.2%) increased as compared
to the corresponding values in the pseudocubic unit cell of bulk stoichiometric LCMO crystals. At T < 150 K, the temperature dependence of the resistivity of LCMO films is well described by the relation ρ = ρ1 + ρ2 (H) T
4.5. The value of ρ 2 decreases with increasing magnetic field and is close to the analogous coefficient for manganite films
grown on substrates with small lattice misfit. 相似文献
15.
Qi Xiao Zhichun Si Jiang Zhang Chong Xiao Zhiming Yu Guanzhou Qiu 《Journal of Materials Science》2007,42(22):9194-9199
Sm3+-doped TiO2 nanocrystalline was synthesized by a sol–gel auto-combustion method and characterized by X-ray diffraction, Brunauer-Emmett-Teller
method (BET), UV–vis diffuse reflectance spectroscopy (DRS), and also photoluminescence (PL) emission spectroscopy. The photocatalytic
activity of Sm3+–TiO2 catalyst was evaluated by measuring degradation rates of methylene blue (MB) under either UV or visible light. The results
showed that doping with the samarium ions significantly enhanced the photocatalytic activity for MB degradation under UV or
visible light irradiation. This was ascribed to the fact that a small amount of samarium dopant simultaneously increased MB
adsorption capacity and separation efficiency of electron-hole pairs. The results of DRS showed that Sm3+-doped TiO2 had significant absorption between 400 nm and 500 nm, which increased with the increase of samarium ion content. The adsorption
experimental demonstrated that Sm3+–TiO2 had a higher MB adsorption capacity than undoped TiO2 and adsorption capacity of MB increased with the increase of samarium ion content. It is found that the stronger the PL intensity,
the higher the photocatalytic activity. This could be explained by the points that PL spectra mainly resulted from surface
oxygen vacancies and defects during the process of PL, while surface oxygen vacancies and defects could be favorable in capturing
the photoinduced electrons during the process of photocatalytic reactions, so that the recombination of photoinduced electrons
and holes could be effectively inhibited. 相似文献
16.
T. Dhandayuthapani R. Sivakumar R. Ilangovan 《Journal of Materials Science: Materials in Electronics》2017,28(20):15074-15080
With arousing interest in the preparation of defect rich TiO2 films for several green energy applications, various methods have emerged in recent days. Herein, we report the properties of blue anatase TiO2 films obtained by combined solvent evaporation and subsequent calcination. The X-ray diffraction and Raman studies indicated the formation of anatase TiO2 films, while the field emission scanning electron microscopic images confirmed the distribution of spherical particles. X-ray photoelectron spectroscopic data revealed the presence of surplus Ti3+ ions and the associated oxygen vacancies. These defect related informations are further evident from the photoluminescence study. The optical study confirmed the extended absorption in the visible region of the blue TiO2 films. These intrinsic defects play a major role in effective charge carrier separation and in tailoring the band gap absorption properties. 相似文献
17.
Novel Bi12TiO20/g-C3N4 composite was successfully prepared with Bi12TiO20 nanoparticles embedded within the fluffy crumpled g-C3N4 nanosheets. Bi12TiO20/g-C3N4 composites exhibit superior photoactivity and stability. As compared with g-C3N4 and Bi12TiO20, the photocatalytic efficiency of Bi12TiO20/g-C3N4 is effectively enhanced about 1.8- and 4.9-fold, respectively. Based on the trapping experiment, ·OH and ·O2? radicals are the dominant reactive oxygen species involved in the photocatalytic process. The proposed Z-scheme mechanism of charge transfer markedly promotes the carriers’ migration and separation, leading to the enhanced photocatalytic performance. 相似文献
18.
Effects of Fe and La addition on the dielectric, ferroelectric, and piezoelectric properties of Bi0.5Na0.5TiO3–Bi0.5Li0.5TiO3–BaTiO3–Mn ceramics were investigated. Similar to the doping effect in lead-based piezoelectric materials, here the Fe-doped ceramic
created a hard effect with an improved mechanical quality factor (Q
m) ~ 160, coercive field (E
c) ~ 2.9 kV/mm, decreased dielectric constant ( e33T /e0 ) ~ 80 3, \left( {\varepsilon_{33}^{T} /\varepsilon_{0} } \right)\sim 80 3, and loss (tanδ) ~ 0.024 while the La-doped one indicated a soft feature with improved piezoelectric constant (d
33) ~ 184 pC/N, e33T /e0 ~ 983, \varepsilon_{33}^{T} /\varepsilon_{0} \,\sim { 983}, tanδ ~ 0.033, and decreased E
c ~ 2.46 kV/mm. In addition, the temperature dependence of the ferroelectric hysteresis loops and strain response under unipolar
electric field was also studied. Around the depolarization temperature T
d, large strain value was obtained with the normalized d33* d_{33}^{*} up to ~1,000 pC/N, which was suggested originated from the development of the short-range order or non-polar phases in the
ferroelectric matrix. All these would provide a new way to realize high piezoelectric response for practical application in
different temperature scale. 相似文献
19.
Superconducting bulks of MgB2 with addition of Sb2O3 and Sb with different stoichiometric compositions ((MgB2) + (Sb2O3)
x
, x = 0.0025, 0.005, 0.015, and (MgB2) + (Sb)y, y = 0.01) were obtained by the Spark Plasma Sintering (SPS) technique. All added samples have high density, above 95% and critical
temperature, T
c, of 38.1–38.6 K. This result and XRD data suggest that Sb does not enter the lattice of MgB2. Impurity phases are Mg3Sb2, MgO, and MgB4. The optimum addition is Sb2O3 for x = 0.005. This sample shows the critical current density, J
c(5 K, 0 T) = 4 × 105 A/cm2 and J
c(5 K, 7 T) = 6 × 102 A/cm2, while the irreversibility field, H
irr (5 K, 100 A/cm2) = 8.23 T. Indicated values of J
c and H
irr are higher than for the pristine sample. The mechanism of J
c and H
irr increase in the Sb2O3 added samples is complex and composed of opposite effects most probably involving morphology elements, the presence of nano
metric MgB4 and the indirect influence of oxygen or oxygen and Sb. Crystallite size of MgB2 is decreasing when Sb-based additions are introduced and the effect is stronger for the Sb-metal addition. The sample with
Sb-metal addition does not improve J
c and H
irr when compared with pristine sample. 相似文献
20.
Alisson H. M. da Silva Thenner S. Rodrigues Anderson G. M. da Silva Pedro H. C. Camargo Janaina F. Gomes José M. Assaf 《Journal of Materials Science》2017,52(24):13764-13778
Here, we have systematically investigated how the nature of the support influenced the oxygen mobility and activities in catalysts comprised of AgPt nanoshells deposited over inorganic oxides. We first synthesized AgPt nanoshells by galvanic replacement reaction between Ag nanospheres and PtCl6 2? (aq) combined with Pt reduction using hydroquinone as an auxiliary reducing agent. The nanoshells were then supported over TiO2, Al2O3 and CeO2. Through this methodology, we prepared materials with similar metallic nanoparticle AgPt compositions (~0.99 wt% Pt), sizes (43 ± 2 nm diameter), spherical shapes, surface morphologies, number of active sites \( (\sim4.5\;\upmu{\text{mol}}\;{\text{g}}_{{{\text{cat}} .}}^{ - 1} ) \) and uniform distribution over the supports, differing only in terms of the nature of the support. The oxide reduction temperature, its capability of re-oxidation and the presence of oxygen mobility were strongly dependent on the metal–support interaction between AgPt nanoshells and oxide supports. These properties have significantly influenced their catalytic performances toward the CO oxidation. At 230 °C, the CO oxidation TOF was 40.4 ± 0.4, 6.9 ± 1, 1.4 ± 0.8 min?1 for AgPt/CeO2, AgPt/TiO2, AgPt/Al2O3, respectively. These differences were attributed to the concentration of oxygen vacancies in each catalyst, which presented exactly the same trend as that of the catalytic activities. Our results may have important contributions to the design of highly active metal oxide-based catalysts toward gas-phase oxidation transformations. 相似文献