电子型超导体(Ln_(1.85)Ce_(0.15))CuO_(4-y)的结构和超导性  

STRUCTURE AND SUPERCONDUCTIVITY ON N-TYPE SUPERCONDUCTORS (Ln_(1.85)Ce_(0.15)) CuO_(4-y)

作　　者：张玉芬[1] 林勤[2] 刘尊孝[2] 

机构地区：[1]北京大学物理化学研究所应用物化研究室,北京100871 [2]北京大学物理系

出　　处：《物理化学学报》1991年第6期641-645,共5页Acta Physico-Chimica Sinica

基　　金：国家超导研究开发中心和国家自然科学基金

摘　　要：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CuO_2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_(1.85)Ce_(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_(1.85)Th_(0.15))CuO_(4-y)和(Eu_(1.85)Ce_(0.15))CuO_(4-y)(Nd_(1.85)Th_(0.15))CuO_(4-y),Nd_2CuO_(4-y)Fy。这类超导体的Tc都在20K左右,载流子是电子,CuO_2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K_2NiF_4型的La_(2-x)Sr_xCuO_4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。In comparison with the structure of hole-doped T phase (La_(2-x)Sr_x)CuO_4, electron-doped superconductors (Ln_(1.85)Ce_(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 LnO_2Ln 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 N_2 atmosphere and superconductivity.

关 键 词：电子型 超导体 结构 超导性 

分 类 号：TM262[一般工业技术—材料科学与工程]