A detailed theoretical model and
experimental study are presented
that formulate and prove the existence of a robust ponderomotive force
(PMF) near the interfaces in a granular dielectric material under
microwave radiation. The model calculations show that the net direction
of the PMF is pore angle-dependent. For most of the pore angles, the
net force is towards the interface creating a mass transport that
fills the interfacial pores and facilitates densification. For small
ranges of angles, near 180o and 360o, PMF drives
the ions in the reverse direction and depletes the pores. However,
the net force for such ranges of angles is small. The PMF also enhances
the diffusion of the mobile ionic species and, consequently, accelerates
the solid-state reaction by increasing the collision probability.
The proof-of-concept experiments show that a mixture of elemental
powders can diffuse, react, and form dense materials when radiated
by the microwave in just a few minutes. Such characteristics, together
with field-induced decrystallization, offer a novel and simple approach
for the synthesis of nanostructured compounds, which can have practical
implications in ceramic technologies and thermoelectric materials.