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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。
This paper studies the formation mechanism of high Tc (2223) phase in Bi-based superconductors. It is proposed that the high Tc phase of Bi-based oxide superconductor is formed by first reacting Sr-Ca-Cu oxide (Ca 0.85 Sr 0.15 CuO 2) with low T c (2212) to form a nucleus with a high Tc phase, The inner 2223-phase core grows into 2223-phase crystal grains in the same manner as the crystal growth in crystallography. There are two routes for the formation of Sr-Ca-Cu oxides in 2223 phase: one is formed from the equilibrium of Ca2CuO3 and SrCaCu5O8 by solid-state reaction and the other is from liquid phase reaction of 2212, Ca2PbO4 and CuO The reaction between the formation of direct. The rate of solid-phase reaction is far less than that of the liquid-phase reaction, so that the formation rate of 2223 phase nucleus is accelerated in the liquid phase reaction. Through the formation mechanism of high Tc phase, it is proposed that the effect of Pb on the formation of high Tc phase in Bi-based superconductors is that it accelerates the nucleation of 2223 phase and does not contribute to the growth of 2223 phase. Finally, using 2223 phase formation mechanism, the texture of the sample is fired.