【摘要】 <正> 自La-Ba（Sr）-Cu-O高温超导体发现以来,已经得到了许多含铜的氧化物超导体,这些超导体中都含有一个Cu以八面体或四方锥配位的CuO₂平面,载流子是空穴。1989年初日本Tokura等人首先发现了电子型超导体(Ln_1.85Ce_0.15)CuO_4-y,Ln=Pr,Nd,Sm。相继报导了这一系列的其他几个超导体:(Pr_1.85Th_0.15)CuO_4-y和(Eu_1.85Ce_0.15)CuO_4-y(Nd_1.85Th_0.15)CuO_4-y,Nd₂CuO_4-yFy。这类超导体的Tc都在20K左右,载流子是电子,CuO₂面内的Cu为四方形配位。将这一类超导体的结构称为T′相结构,相应地称K₂NiF₄型的La_2-xSr_xCuO₄的结构为T相结构。两种晶体结构示于图1。两年多来,寻找更高T_c的电子型超导体是超导界所关心的问题之一,具更多还原

【Abstract】 In comparison with the structure of hole-doped T phase (La_2-xSr_x)CuO₄, electron-doped superconductors (Ln_1.85Ce_0.15)CuO_4-y, Ln=Pr, Nd, Sm, Eu, possess T phase structure with tetragonal I4/mmm symmetry. Their structural features are that the Cu ion is coordinated by four oxygen ions in square planar form and the Ln ion is located in octa-coordinate cubic site in the fluorite type LnO₂Ln duble layers. In this paper, the effects of preparation condition and cation substitution on the structure and superconductivity have been studied. Average ionic radius of Ln-site is limited in very narrow range. It can be changed by the substitution of larger or smaller ions. Its dimension is very important for structural type, structural stability under N₂ atmosphere and superconductivity.更多还原