【摘要】 <正> 自M.K.Wu等发现高T_cYBa₂Cu₃O_7-δ超导体以来,人们从各个不同的角度对这个体系进行了大量的研究工作,对它的制备、结构、性能及应用都有了一定的认识。我们在制备高T_cYBa₂Cu₃O_7-δ超导体时,发现在摄氏900℃以上的高温,烧结温度仅差十几度足以引起超导性能的明显差别,这是令人难以理解的。为此有必要对达个体系在烧结过程中的相变、氧含量变化及各相的结构作进一步的研究,以求弄清YBa₂Cu₃O_7-δ超导相生成的机理。更多还原

【Abstract】 The Y-Ba-Cu mixed oxide system is obtained when any kinds of materials containing Y, Ba, Cu are heated at 850℃. when heated to 900℃, an oxygen-rich tetragonal phase I (YBa₂Cu₃O_6.9) is formed. At 930℃, an oxygen-deficient tetragonal phase Ⅱ （YBa₂Cu₃O₆） appears, and the oxygens at positions （1/2, 0,0） and （0,1/2,0） are almost drived out. The oxygen absorbed above 650℃ are equally distributed onto （1/2,0,0） and （0,1/2,0）, the amount of which varies with temperature. It is absorbed oxygen that migrates easily from （0,1/2,0）to （1/2,0,0）as the tetragonal phase transits into the orthorhombic phase at 650℃, which makes differences in oxygen-ocupancy at these two positions, such that the structure deviates from tetragonality and the superconduting properties are improved.更多还原