固相反应时Bi_(1.92)Pb_(0.32)Sr_2Ca_(1.7)Mg_(0.3)Cu_(3.07)O_x超导体中2223相的生长

GROWTH OF 2223 PHASE IN Bi_(1.92)Pb_(0.32)Sr_2Ca_(1.7)Mg_(0.3)Cu_(3.07)O_x SUPERCONDUCTOR IN THE PROCESS OF SOLID STATE REACTION

用固相反应法合成了名义组分为Bi_(1.92)Pb_(0.32)Sr_2Ca_(1.7)Mg_(0.3)Cu_(3.67)O_5的块状样品。X射线衍射谱(XRD)、扫描电子显微镜(SEM)和电子探计X射线分析(EDAX)结果以及块状和粉状试样的交流磁化率测量表明,样品中存在110和85K两个超导相;2223相(110K)首先在2212相(85K)晶体的晶界和外部区域生成。本文认为,最初存在于2212相中的2223相相当于堆垛层错,随着位错攀移,CaCuO_2层插入2212相晶格中从而使2223相形成和长大。实验数据的计算结果支持了这一观点。

Samples with nominal composition Bi1.92 Pb0.32 Sr2 Ca1.7 Mg0.3 Gu3.07 Ox were synthesized by solid state reaction. The results of XRD, SEM, EDAX and ac susceptibility measurement on the block and the power samples showed that in the samples there coexisted the 110K and 85K superconducting phases. The 2223 phase (110K) is considered to form at first at boundaries and in the outer region of the crystals of the 2212 phase (85K). We also believe that the origin of the structure of 2223 phase may initally exist in the 2212 phase grains and dact ad certain kind of stacking faults, and the 2223 phase finally forms and grows through the intercalation of the CaCuO2 layers in the crystal lattice of the 2212 phase together with climbing of dislocations. A calculation pased on experimental data supports this point of view.