Abstract:
It is a noted fact that the composition of a mixed solid phase grown at non-equilibrium can deviate from the equilibrium composition due to the very low diffusion rate in the solid phase. We present an analytical model for the determination of the kinetic composition of a binary solid phase that is growing from a solution at a given supersaturation, giving rise to kinetic phase diagrams. The model is derived for growth at rough surfaces but is expected to apply also to growth at non-roughened surfaces. Kinetic phase diagrams for different undercooling and excess energy parameters are presented and discussed. If the interaction parameters, describing the excess free energy, are large the model equations can have two stable solutions, which implies the simultaneous growth of two solid phases with different compositions. This kinetic phase separation depends on the undercooling and the composition dependence of the attachment probabilities.