Fe/Dy非晶多层膜晶化反应的热力学及动力学研究

由Miedema半经验公式计算出了Fe Dy二元系自由能图以揭示Fe Dy非晶多层膜的晶化本质。晶化受热力学和动力学两种因素控制 ,Fe,Dy晶态自由能低于初始非晶态 ,提供了晶化的热力学驱动力 ,而形核势垒及临界晶核尺寸控制了晶化反应的相选择 ,因而中等温度退火时先出现Fe晶粒 ,继而Dy晶粒 ,不出现金属间化合物。

Thermodynamic and Kinetic Study on Crystallization Reaction of Amorphous Fe/Dy Multilayers

To give further insight into the behaviour of Fe/Dy multilayers in the crystallization from the as deposited amorphous state, the free energy diagram of Fe/Dy system was constructed based on Miedema semiempirical theory. It is shown that the crystallization of the amorphous films is controlled by both thermodynamic and kinetic conditions. The calculated free energies of crystalline Fe and Dy are significantly lower than those of amorphous ones, which supply the thermodynamic driving force for the crystallization. During annealing the phase evolution of the multilayers is controlled by the free energy barrier of nucleation and the radius of critical sized nucleus of new phases. Thus it explains the experimental results that crystallites of Fe formed first and then followed by Dy grains, whereas crystalline intermetallic compounds were not observed during annealing at moderate temperatures.