The particle sizes of ultrafine powders are between cluster and fine powders, with theparticle diameters generally in the range of 1--100nm. When compared with commonmaterials consisting of bigger particles, materials...The particle sizes of ultrafine powders are between cluster and fine powders, with theparticle diameters generally in the range of 1--100nm. When compared with commonmaterials consisting of bigger particles, materials consisting of nanometer-size particleshave many special properties. These include small-sized effect, surface and interface展开更多
By comprehensively determining the lattice parameter, XPS, Mssbauer spectrum, relationship between the resistance and the temperature, oxygen content and the thermal decomposition temperature of the samples of YBa_2Cu...By comprehensively determining the lattice parameter, XPS, Mssbauer spectrum, relationship between the resistance and the temperature, oxygen content and the thermal decomposition temperature of the samples of YBa_2Cu_(3-x)Sn_xO_(7+y) system, it is discovered that Sn occupies the site of Cuin the form of Sn^(4+) oxidation state. The change of crystalline structure as well as T_c are very little for x<0.4. The oxygen content of the samples is increased by the substitution of Sn for Cu, which influences the valence of Cu obviously, and makes the Cu be in the Cu^(3+) state. The experimental results give some important information on understanding the origin of superconductivity from the structure, oxygen deficiency, and electronic state. From analysis, it is suggested that the coupling strength between metals and oxygen determines the superconductivity.展开更多
基金National Natural Science Foundaion of ChinaChinese Academy of Sciences
文摘The particle sizes of ultrafine powders are between cluster and fine powders, with theparticle diameters generally in the range of 1--100nm. When compared with commonmaterials consisting of bigger particles, materials consisting of nanometer-size particleshave many special properties. These include small-sized effect, surface and interface
文摘By comprehensively determining the lattice parameter, XPS, Mssbauer spectrum, relationship between the resistance and the temperature, oxygen content and the thermal decomposition temperature of the samples of YBa_2Cu_(3-x)Sn_xO_(7+y) system, it is discovered that Sn occupies the site of Cuin the form of Sn^(4+) oxidation state. The change of crystalline structure as well as T_c are very little for x<0.4. The oxygen content of the samples is increased by the substitution of Sn for Cu, which influences the valence of Cu obviously, and makes the Cu be in the Cu^(3+) state. The experimental results give some important information on understanding the origin of superconductivity from the structure, oxygen deficiency, and electronic state. From analysis, it is suggested that the coupling strength between metals and oxygen determines the superconductivity.
