摘要
本文研究Bi系超导体高Tc(2223)相的形成机制。提出Bi系氧化物超导体高Tc相的形成过程是:首先Sr-Ca-Cu氧化物(Ca_(0.85)Sr_(0.15)CuO_2)与低Tc(2212)相反应形成高Tc相的核,然后样品内2223相核通过象结晶学中晶体生长那样的方式长大成2223相晶粒。2223相成核过程中Sr-Ca-Cu氧化物的形成途径有两条:一条是通过固相反应从Ca_2CuO_3和SrCaCu_5O_8的平衡中形成;另一条是通过液相反应从2212相,Ca_2PbO_4和CuO之间的反应直接形成。固相反应的速度远小于液相反应的速度,从而2223相核的形成速度在液相反应下得到加快。通过高Tc相的形成机制,提出Pb对Bi系超导体高Tc相形成的作用是:它只加速2223相的成核,而对2223相的成长不起作用。最后利用2223相形成机制,烧制出具有织构的样品。
In this paper, the formation process of high-Tc phase in Bi-based supercondutor is investigated by X-ray diffraction etc. The high-Tc phase might be formed in the following manner. At first, the nuclei of hig-Tc (2223) phase are formed by the reaction of Sr-Ca-Cu oxide with low-Tc (2212) phase; Then the nuclei of 2223 phase grows, following the manner of ordinary crystal growth. There are two ways to form Sr-Ca-Cu oxide. One is accomplished by solid state reaction between Ca2CuO3 and Ca3(1-x) Sr3xCu5O8, and the other by liquid-state reaction of Ca2PbO4, 2212 phase and CuO. The liquid-state reaction rate is much quicker than that of solid state reaction. So, the rate of formation of 2223 nuclei can be accderated in liquid-state reaction. Based on this mechanism, we propose that Pb can only accelerate the nucleation of 2223 phase and exert no significant influence on the growth of 2223 phase.
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
1992年第4期649-654,共6页
Acta Physica Sinica
基金
国家超导技术联合研究开发中心资助的课题
