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用化学动力学探讨了Bi系超导相形成的机理,提出反应活化能是控制超导相形成的关键因素。在纯Bi系2223名义成份下,2212相的形成满足“晶核形成生长”自催化动力学模型,其动力学方程为α_(2212)=1—exp(—k_(2212)t~(2.5))。2223相的形成较好地符合“收缩晶核界面”反应模型,动力学方程为1—(1—α_(2223))~(1/3)=k_(2223)t。以0.35molPb替代Bi后,2212相形成的动力学规律没有本质改变,但是2223相的形成表现出区域反应的自催化效应,其相应的动力学方程为α_(2223)=1—exp(—k_(2223t)。
The formation mechanism of Bi-based superconducting phases was discussed by chemical kinetics, and the reaction activation energy was the key factor for controlling the formation of superconducting phases. Under the pure Bi 2223 nominal composition, the formation of 2212 phase satisfies the autocatalytic kinetic model of “nucleation and growth” with the kinetic equation of α 2212 = 1-exp (-k 2212) t 2.5, ). The formation of 2223 phase is in good agreement with the model of “shrinking nucleation interface”. The kinetic equation is 1- (1-α 2223) ~ (1/3) = k 2223 t. However, the formation of 2223 phase shows the autocatalytic effect of the regional reaction. The corresponding kinetic equation is α 2223 = 1-exp (-k_ (2223t).