A model is presented to describe a compensation mechanism for semi-insulating 6H-SiC grown with the intentional doping of vanadium. Because we found nitrogen to be the principal shallow donor impurity in SiC by second...A model is presented to describe a compensation mechanism for semi-insulating 6H-SiC grown with the intentional doping of vanadium. Because we found nitrogen to be the principal shallow donor impurity in SiC by secondary ion mass spectroscopy （SIMS） measurements, semi-insulating properties in SiC are achieved by compensating the nitrogen donor with the vanadium deep acceptor level. The presence of different vanadium charge states V^3＋ and V^4＋ is detected by electron paramagnetic resonance and optical absorption measurements,which coincides with the results obtained by SIMS measurements. Both optical absorption and low temperature photoluminescence measurements reveal that the vanadium acceptor level is located at 0.62eV below the conduction band in 6H-SiC.展开更多
6H-SiC bulk crystals have been prepared by sublimation method in an inductively heated growth reactor. The effect of nitrogen doping on absorption for 6H-SiC was investigated. The absorption measurement based on optic...6H-SiC bulk crystals have been prepared by sublimation method in an inductively heated growth reactor. The effect of nitrogen doping on absorption for 6H-SiC was investigated. The absorption measurement based on optical method is a non-destructive and non-contact method. The band-gap narrowing with higher doping concentration was observed. For n-type doping below band-gap absorption band at 623 nm for 6H-SiC was observed. The peak intensity of the absorption band increased with increasing charge carrier concentration obtained from Hall measurements. It is also found that the nitrogen doping level decreased in the radial direction and it was the highest at the beginning of growth.展开更多
W<sup>6+</sup>-doped TiO<sub>2</sub> was prepared by sodium tungsten (VI) and titanium sulfate with sodium dodecyl sulfate as surfactant under microwave irradiation. The samples were characteri...W<sup>6+</sup>-doped TiO<sub>2</sub> was prepared by sodium tungsten (VI) and titanium sulfate with sodium dodecyl sulfate as surfactant under microwave irradiation. The samples were characterized by X-ray diffraction (XRD) and Scanning electron micrograph (SEM). The results showed that the as-prepared nanocomposite of inventory molar ratio of 2% calcined at 500°C for 2 h was anatase. The SEM showed that the majority of the catalyst was a relatively flake structure, and some fine particles attached to it. We also studied the photocatalytic activity of the as-prepared samples by using degradation of methyl orange. The factors including inventory molar ratio and concentration of W<sup>6+</sup>-doped, calcined temperature, amount of hydrogen peroxide and acidity of solution were investigated. When the catalyst was 1.0 g/L, pH was 2, C(H<sub>2</sub>O<sub>2</sub>) was 3 mL/L, the degradation rate of TiO<sub>2</sub> for methyl orange of 20 mg/L reached 79.63% in 40 min.展开更多
The rare earth ion Yb^3+ doped Bi2WO6 photocatalysts were synthesized by hydrothermal method.Moreover,XRD,XPS,FESEM,TEM,Ramam,N2 adsorption-desorption isotherm measurements and UV-vis diffusion reflectance spectra wer...The rare earth ion Yb^3+ doped Bi2WO6 photocatalysts were synthesized by hydrothermal method.Moreover,XRD,XPS,FESEM,TEM,Ramam,N2 adsorption-desorption isotherm measurements and UV-vis diffusion reflectance spectra were used to characterize the Yb^3+ doped Bi2WO6 photocatalysts.The morphology,specific surface area,and pore volume distribution were greatly affected after Yb3+ ions doping.Photocatalytic performance of Bi2WO6 was effectively enhanced after Yb3+ ions doping,6% Yb^3+ doped Bi2WO6 had the best photocatalytic performance,and 96.2% Rhodamine B was degradated after irradiated 30 min,which was 1.29 times that of the pristine one.The enhanced photocatalytic performance was due to the increased specific surface area,decreased energy band gap and inhibition of photoelectron-hole recombination after Yb3+ ions doping.展开更多
Thermoelectric properties of Li-doped Sr0.70Ba0.30Nb2O6-δ ceramics were investigated in the temperature range from 323 K to 1073 K. The electrical conductivity increases significantly after lithium interstitial dopin...Thermoelectric properties of Li-doped Sr0.70Ba0.30Nb2O6-δ ceramics were investigated in the temperature range from 323 K to 1073 K. The electrical conductivity increases significantly after lithium interstitial doping. However, both of the magnitudes of Seebeck coefficient and electrical conductivity vary non-monotonically but synchronously with the doping contents, indicating that doped lithium ions may not be fully ionized and oxygen vacancy may also contribute to carriers. The lattice thermal conductivity increases firstly and then decreases as the doping content increases, which is affected by competing factors.Thermoelectric performance is enhanced by lithium interstitial doping due to the increase of the power factor and the thermoelectric figure of merit reaches maximum value （0.21 at 1073 K） in the sample Sr0.70Ba0.30Li0.10Nb2O6.展开更多
The nitrogen-doped porous TiO2 layer on Ti6Al4V substrate was fabricated by plasma-based ion implantation of He, O and N. In order to increase the photodegradation efficiency of TiO2 layer, two methods were used in th...The nitrogen-doped porous TiO2 layer on Ti6Al4V substrate was fabricated by plasma-based ion implantation of He, O and N. In order to increase the photodegradation efficiency of TiO2 layer, two methods were used in the process by forming mesopores to increase the specific surface area and by nitrogen doping to increase visible light absorption. Importantly, TiO2 formation, porosity architectures and nitrogen doping can be performed by implantation of He, O and N in one step. After implantation, annealing at 650 ℃ leads to a mixing phase of anatase with a little rutile in the implanted layer. By removing the near surface compact layer using argon ion sputtering, the meso-porous structure was exposed on surfaces. Nitrogen doping enlarges the photo-response region of visible light. Moreover, the nitrogen dose of 8×1015 ion/cm2 induces a stronger visible light absorption. The photodegradation of rhodamine B solution with visible light sources indicates that the mesopores on surfaces and nitrogen doping contribute to an apparent increase of photocatalysis efficiency.展开更多
Zr4＋ doped Bi2WO6 was prepared by a fast microwave-assisted hydrothermal method and used for photocatalytic degradation of organic dyes. The as-prepared samples were characterized by X-ray diffraction（XRD）, transmi...Zr4＋ doped Bi2WO6 was prepared by a fast microwave-assisted hydrothermal method and used for photocatalytic degradation of organic dyes. The as-prepared samples were characterized by X-ray diffraction（XRD）, transmission electron microscopy（TEM） and UV-Vis spectroscopy. The results indicate that cell volume of Bi2WO6 has a slight increase dependent on the substitution of W6＋ by Zr4＋ with increasing the Zr doping amount. The photocatalytic performance of Zr4＋ doped Bi2WO6 was evaluated by the photodegradation of MO under visible light irradiation. Compared with samples obtained with traditional hydrothermal method as well as pure Bi2WO6, an obviously improved photocatalytic efficiency of Zr4＋ doped Bi2WO6 is achieved by this microwave-assisted hydrothermal way. The 3% Zr doped Bi2WO6 sample exhibited the best photocatalytic activity, which is probably because of the appropriate proportion of components and optimum amount of oxygen vacancies of the sample.展开更多
文摘A model is presented to describe a compensation mechanism for semi-insulating 6H-SiC grown with the intentional doping of vanadium. Because we found nitrogen to be the principal shallow donor impurity in SiC by secondary ion mass spectroscopy （SIMS） measurements, semi-insulating properties in SiC are achieved by compensating the nitrogen donor with the vanadium deep acceptor level. The presence of different vanadium charge states V^3＋ and V^4＋ is detected by electron paramagnetic resonance and optical absorption measurements,which coincides with the results obtained by SIMS measurements. Both optical absorption and low temperature photoluminescence measurements reveal that the vanadium acceptor level is located at 0.62eV below the conduction band in 6H-SiC.
基金the National Natural Science Foundation of China (No. 50472068)Natural Science Foundation of Shandong Province,(No. Y2006F15)+1 种基金Shandong Provincial Significant Science and Technology Attack Project (No. 2005GG2107001)Shandong Provincial Independent Innovation Significant Science and Technology Special Plan (No. 2006GG1103046)
文摘6H-SiC bulk crystals have been prepared by sublimation method in an inductively heated growth reactor. The effect of nitrogen doping on absorption for 6H-SiC was investigated. The absorption measurement based on optical method is a non-destructive and non-contact method. The band-gap narrowing with higher doping concentration was observed. For n-type doping below band-gap absorption band at 623 nm for 6H-SiC was observed. The peak intensity of the absorption band increased with increasing charge carrier concentration obtained from Hall measurements. It is also found that the nitrogen doping level decreased in the radial direction and it was the highest at the beginning of growth.
文摘W<sup>6+</sup>-doped TiO<sub>2</sub> was prepared by sodium tungsten (VI) and titanium sulfate with sodium dodecyl sulfate as surfactant under microwave irradiation. The samples were characterized by X-ray diffraction (XRD) and Scanning electron micrograph (SEM). The results showed that the as-prepared nanocomposite of inventory molar ratio of 2% calcined at 500°C for 2 h was anatase. The SEM showed that the majority of the catalyst was a relatively flake structure, and some fine particles attached to it. We also studied the photocatalytic activity of the as-prepared samples by using degradation of methyl orange. The factors including inventory molar ratio and concentration of W<sup>6+</sup>-doped, calcined temperature, amount of hydrogen peroxide and acidity of solution were investigated. When the catalyst was 1.0 g/L, pH was 2, C(H<sub>2</sub>O<sub>2</sub>) was 3 mL/L, the degradation rate of TiO<sub>2</sub> for methyl orange of 20 mg/L reached 79.63% in 40 min.
基金the National Natural Science Foundation of China(No.51662005)。
文摘The rare earth ion Yb^3+ doped Bi2WO6 photocatalysts were synthesized by hydrothermal method.Moreover,XRD,XPS,FESEM,TEM,Ramam,N2 adsorption-desorption isotherm measurements and UV-vis diffusion reflectance spectra were used to characterize the Yb^3+ doped Bi2WO6 photocatalysts.The morphology,specific surface area,and pore volume distribution were greatly affected after Yb3+ ions doping.Photocatalytic performance of Bi2WO6 was effectively enhanced after Yb3+ ions doping,6% Yb^3+ doped Bi2WO6 had the best photocatalytic performance,and 96.2% Rhodamine B was degradated after irradiated 30 min,which was 1.29 times that of the pristine one.The enhanced photocatalytic performance was due to the increased specific surface area,decreased energy band gap and inhibition of photoelectron-hole recombination after Yb3+ ions doping.
基金supported by the National Basic Research Program of China(Grant No.2013CB632506)the National Natural Science Foundation of China(Grant Nos.51202132,51231007,and 11374186)
文摘Thermoelectric properties of Li-doped Sr0.70Ba0.30Nb2O6-δ ceramics were investigated in the temperature range from 323 K to 1073 K. The electrical conductivity increases significantly after lithium interstitial doping. However, both of the magnitudes of Seebeck coefficient and electrical conductivity vary non-monotonically but synchronously with the doping contents, indicating that doped lithium ions may not be fully ionized and oxygen vacancy may also contribute to carriers. The lattice thermal conductivity increases firstly and then decreases as the doping content increases, which is affected by competing factors.Thermoelectric performance is enhanced by lithium interstitial doping due to the increase of the power factor and the thermoelectric figure of merit reaches maximum value （0.21 at 1073 K） in the sample Sr0.70Ba0.30Li0.10Nb2O6.
基金Project(20040213048) supported by the Specialized Research Fund for the Doctoral Program of Higher Education of ChinaProject(20090450737) supported by the China Postdoctoral Science Foundation
文摘The nitrogen-doped porous TiO2 layer on Ti6Al4V substrate was fabricated by plasma-based ion implantation of He, O and N. In order to increase the photodegradation efficiency of TiO2 layer, two methods were used in the process by forming mesopores to increase the specific surface area and by nitrogen doping to increase visible light absorption. Importantly, TiO2 formation, porosity architectures and nitrogen doping can be performed by implantation of He, O and N in one step. After implantation, annealing at 650 ℃ leads to a mixing phase of anatase with a little rutile in the implanted layer. By removing the near surface compact layer using argon ion sputtering, the meso-porous structure was exposed on surfaces. Nitrogen doping enlarges the photo-response region of visible light. Moreover, the nitrogen dose of 8×1015 ion/cm2 induces a stronger visible light absorption. The photodegradation of rhodamine B solution with visible light sources indicates that the mesopores on surfaces and nitrogen doping contribute to an apparent increase of photocatalysis efficiency.
基金supported by the China Postdoctoral Science Foundation(2014M550337)Natural Science Foundation of High Education School of Anhui Province(KJ2013A091)+1 种基金Science and Technology Project of Anhui Province(1604a0802122)Fund of Key Laboratory of Optoelectronic Materials Chemistry and Physics,Chinese Academy of Sciences
文摘Zr4＋ doped Bi2WO6 was prepared by a fast microwave-assisted hydrothermal method and used for photocatalytic degradation of organic dyes. The as-prepared samples were characterized by X-ray diffraction（XRD）, transmission electron microscopy（TEM） and UV-Vis spectroscopy. The results indicate that cell volume of Bi2WO6 has a slight increase dependent on the substitution of W6＋ by Zr4＋ with increasing the Zr doping amount. The photocatalytic performance of Zr4＋ doped Bi2WO6 was evaluated by the photodegradation of MO under visible light irradiation. Compared with samples obtained with traditional hydrothermal method as well as pure Bi2WO6, an obviously improved photocatalytic efficiency of Zr4＋ doped Bi2WO6 is achieved by this microwave-assisted hydrothermal way. The 3% Zr doped Bi2WO6 sample exhibited the best photocatalytic activity, which is probably because of the appropriate proportion of components and optimum amount of oxygen vacancies of the sample.
