【摘要】 对不同组分及烧结条件下的Ba_xY_1-xCuO_3-y多相和Ba₂YCu₃O_9-δ单相超导氧化物分别作了电阻、交流磁化率和比热随温度的变化,以及X射线衍射、X射线光电子谱的测量。结果支持样品中存在大块超导电性的观点,其中对超导起主要作用的是Ba₂YCu₃O（9-δ）相。并且对于较高Tc的样品具有较大的Fermi面态密度。但含Ba量仅为0.5％（x= 0.005）的样品仍可导致非界面的高温超导电性。因此不能排除Ba以杂质原子身份影响电子结构,从而导致超导电性的可能性。另外,在x=0处观察到可能由电子推动的金属-半导体相变。更多还原

【Abstract】 The temperature dependence of resistance, a.c. susceptibility, specific heat, XPS and X-ray diffraction were measured respectively both in single-phase Ba₂YCu₃O_9-δ and multi-phase Ba_xY_1-xCuO_3-y samples with different compositions prepared at various sintering conditions. The experimental results support such a view that a bulk superconductivity exists in these compounds. We also found the Ba₂YCu₃O_9-δphase plays an important part in the superconductivity of the multi-phase samples, and the high density of electronic state at Fermi level is usually associated with the high Tc. But only 0.5% （x=0.005） content of Ba still leads to high Tc superconductivity which should not attribute to the interface. As a result, we may not rule out the possibility that Ba atom acts as an impurity to affect the electronic structure, thus leading to supercoductivity. It has also been observed that the M-S （Metal-Semiconductor） transition, which might be driven by the electrons, occurs near x=0.更多还原