Making amorphous and crystalline alloys by solid state interdiffusion

Abstract

Methods for synthesizing solid-state crystalline alloys and products made therefrom are disclosed. Plural repeat units, each comprising an ordered sequence of superposed layers of preselected solid-state reactants, are formed superposedly on a surface of a solid substrate to form a modulated composite of the reactants. The layers comprising a repeat unit are controllably formed to have relative thicknesses corresponding to the stoichiometry of a preselected solid compound found on a phase diagram of the reactants. Each repeat unit also has a repeat-unit thickness no greater than a critical thickness for a diffusion couple of the reactants, where the repeat-unit thickness is preferably less than or equal to about 100 .ANG.. The modulated composite is then heated to an interdiffusion temperature lower than a nucleation temperature for the reactants for a time sufficient to form an amorphous alloy of the reactants having a stoichiometry corresponding to the preselected solid compound. The amorphous alloy is then heated to a nucleation temperature to initiate crystallization of the alloy. The methods described herein allow control of the outcome of a solid-state synthesis pathway in part by controlling which intermediate(s) are formed.