摘要
用固态反应法制备了YBa2 Cu3 -xFexOy(x =0— 0 .5 )一系列样品 ,反应在空气中进行 .运用正电子湮没技术、扫描电子显微镜和X射线衍射进行了研究 ,并测定了氧含量 .正电子湮没结果发现 ,x =0 .12时短寿命分量τ1和长寿命分量τ2 都存在一异常变化 .X射线衍射和扫描电子显微镜研究分别表明 ,材料在x =0 .12— 0 .15区间内发生正交 四方相变 ,晶粒尺寸突然由小变大 .通过对上述实验结果的分析可以得到 ,在该类材料中 ,正电子对结构相变十分敏感 ;另外 ,当Fe掺杂量增大到一定程度时 。
A series of YBa2Cu3-xFexOy (x = 0-0.5)samples were prepared in air by the standard solid-state-reaction method. The crystal structures and physical properties have been studied by means of positron annihilation technology (PAT), scan electronic microscope (SEM) and X-ray diffraction (XRD). Oxygen contents of the samples were determined by a volumetric method. The results of PAT show that the short lifetime component tau (1) and long lifetime component tau (2) are all changed anomalously between x = 0.12 and 0.15 where the compounds undergo the orthorhombic-tetragonal (O-T) phase transition. In addition,the grain size of the sample with x = 0.15 is much larger than that of samples with x<0.15. Based on the experimental results,we obtain the following conclusions. The positron can be used as a sensitive probe for O-T phase transition in this system. When x>0.15, the doped Fe atoms and incoming oxygens tend to associate into clusters rather than to randomly distribute over the crystal lattice. The cluster behavior is in agreement with the results of theory and other experimental results.
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2001年第4期769-774,共6页
Acta Physica Sinica
基金
国家重点基础研究专项基金 !(批准号 :NKBRSF -G19990 64 6)
国家自然科学基金 !(批准号 :198740 17)资助的课题&&
