Interfacial ponderomotive force in solids leads to field induced dissolution of materials and formation of non-equilibrium nanocomposites

We report that microwave radiation can decompose continuous solid-solution materials into their constituent phases - a process that is thermodynamically unfavorable at equilibrium. A detailed analysis of the interaction of the electromagnetic wave with the material showed that a strong ponderomotive force preferentially separates the constituent phases via an enhanced mass transport process amplified particularly near the interfaces. The proof of concept experiments showed that the material, whether it is a solid-solution of two elements, e.g. (Si1-xGex), or two compounds, e.g. (Bi2Te3)(1-x)(Sb2Te3)(x), decomposes into the constituent phases when radiated by a polarized microwave field. The dissolution happens in the bulk of the material and even below the melting point. The degree of decomposition can be controlled by radiation parameters to produce structures composed of gradient phases of the solid-solution. This offers a novel and facile method for synthesizing gradient composite and complex structures for application in thermoelectricity as well as fabrication of core-shell structures for catalysts and biomedical applications. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.