Resistance as a function of temperature for optimally doped manganese perovskites is simulated based on a random resistor network model which is generated through the Monte Carlo method by identifying neighbours in ea...Resistance as a function of temperature for optimally doped manganese perovskites is simulated based on a random resistor network model which is generated through the Monte Carlo method by identifying neighbours in each cubic lattice randomly occupied by ferromagnetic metallic particles. Only one parameter, i.e. the number density of ferromagnetic particles, is used as an adjustable parameter, and it is shown that the model yields excellent agreement with measured resistance data in (La_(1-x)Y_(x))_(2/3)Ca_(1/3)MnO_(3) (0 ≤ x ≤ 0.2) for temperatures covering the whole range from the high-T insulating bebaviour to the low-T metallic state.展开更多
The reduction of CuO with different amount of carbon(CuO:C=2:1,2:1.5,and 2:2,in molar ratio)induced by ball milling is examined by x-ray diffraction and transmission electron microscopy.It is found that reduction proc...The reduction of CuO with different amount of carbon(CuO:C=2:1,2:1.5,and 2:2,in molar ratio)induced by ball milling is examined by x-ray diffraction and transmission electron microscopy.It is found that reduction process is closely related to the carbon content.CuO can be completely converted into Cu if an excessive C is used(i.e.,C=1.5 or 2.0mol).However,the reduction of CuO follows a two-step process,CuO→Cu→Cu2O,if the mixture only contains a nominal C content(i.e.,C=1 mol).A tentative model in terms of solid state reaction at the interfaces is proposed to explain the effect of carbon content on the mechanoreduction of CuO.展开更多
We study the effects of film thickness on lattice parameters, direct band gap and photovoltaic outputs in the sol-gel derived BiFeO3 thin films. With the change of the film thickness, the great transitions will take p...We study the effects of film thickness on lattice parameters, direct band gap and photovoltaic outputs in the sol-gel derived BiFeO3 thin films. With the change of the film thickness, the great transitions will take place in the preferred orientation and lattice parameters. Furthermore, the photovoltaic outputs are significantly dependent on the film thickness. The results show that the open circuit voltage gradually increases and the short circuit current reciprocally decreases with the increase of film thickness. In particular, we demonstrate for the first time that there are tunable photovoltaic outputs with external electric field polarization switching in the polycrystalline BiFeO3 film, which is critical for the future device applications based on the photovoltaic properties of BiFeO3 films.展开更多
基金Supported by the Trans-Century Training Programme Foundation for Talents by the Ministry of Education.
文摘Resistance as a function of temperature for optimally doped manganese perovskites is simulated based on a random resistor network model which is generated through the Monte Carlo method by identifying neighbours in each cubic lattice randomly occupied by ferromagnetic metallic particles. Only one parameter, i.e. the number density of ferromagnetic particles, is used as an adjustable parameter, and it is shown that the model yields excellent agreement with measured resistance data in (La_(1-x)Y_(x))_(2/3)Ca_(1/3)MnO_(3) (0 ≤ x ≤ 0.2) for temperatures covering the whole range from the high-T insulating bebaviour to the low-T metallic state.
文摘The reduction of CuO with different amount of carbon(CuO:C=2:1,2:1.5,and 2:2,in molar ratio)induced by ball milling is examined by x-ray diffraction and transmission electron microscopy.It is found that reduction process is closely related to the carbon content.CuO can be completely converted into Cu if an excessive C is used(i.e.,C=1.5 or 2.0mol).However,the reduction of CuO follows a two-step process,CuO→Cu→Cu2O,if the mixture only contains a nominal C content(i.e.,C=1 mol).A tentative model in terms of solid state reaction at the interfaces is proposed to explain the effect of carbon content on the mechanoreduction of CuO.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11174092 and 11374181, the Doctoral Program of the Ministry of National Education under Grant No 20100142110068, and the Fundamental Research Funds for the Central Universities under Grant No HUST 0118012006.
文摘We study the effects of film thickness on lattice parameters, direct band gap and photovoltaic outputs in the sol-gel derived BiFeO3 thin films. With the change of the film thickness, the great transitions will take place in the preferred orientation and lattice parameters. Furthermore, the photovoltaic outputs are significantly dependent on the film thickness. The results show that the open circuit voltage gradually increases and the short circuit current reciprocally decreases with the increase of film thickness. In particular, we demonstrate for the first time that there are tunable photovoltaic outputs with external electric field polarization switching in the polycrystalline BiFeO3 film, which is critical for the future device applications based on the photovoltaic properties of BiFeO3 films.
