Bi_2Sr_2CaCu_2O_(8+δ)的定向凝固及超导转变

DIRECTIONAL SOLIDIFICATION AND SUPERCONDUCTIVE TRANSITION OF Bi_2Sr_2CaCu_2O_(8+δ)

该文利用激光浮区熔化晶体生长法,在0.1到14.0mm/min凝固速度下非平衡凝固出不同组织的Bi_2Sr_2CaCu_2O_(8+δ)定向生长棒。在较慢速度下,能得到较直且长的条状(Sr_(1-x)Ca_x)CuO_2相和富Cu的白点相,并且随着凝固速度的增加,(Sr_(1-x)Ca_x)CuO_2相逐渐变细,富Cu白点相也逐渐变小和弥散分布;当凝固速度很快时,析出另一亚稳相(Sr_(1-x)Ca_x)Cu_2O_3。半导体性质的定向生长棒向超导体转变的退火过程实际上是亚稳相的包析反应,退火温度和时间都对反应有影响。

By using laser floating zone melting technology, Bi2Sr2CaCu2O(?) as -grown fibers with different morphologies were solidified in nonequilibrium condition at rates between 0.1 and 14.0mm/min. At low rate, a (Sr1-xCax)CuO2 phase with long and straight strips in shape and a white Cu-rich having a morphology of dotted shape were found. With increasing cooling rate, the phase (Sr1-xCax)CuO2 becomes thinner and the Cu -rich phase becomes smaller and dispersive. When the cooling rate is fast, another unstable phase (Sr1-xCax)Cu2O3 occurred.As a matter of fact,the annealing temperature and time influence the transition of the semicond-uctive as-grown fiber to superconductor which is a peritectoid reaction.