  In superionic compounds one component pre-melts providing high ionic
conductivity to solid state electrolytes. Here, we find sublattice melting in
colloidal crystals of oppositely charged particles that are highly asymmetric
in size and charge in salt solutions. The small particles in ionic compounds
melt when the temperature increases forming a superionic phase. These
delocalized small particles in a crystal of large oppositely charged particles,
in contrast to superionic phases in atomic systems, form crystals with
non-electroneutral stoichiometric ratios. This generates structures with
multiple domains of ionic crystals in percolated superionic phases with
adjustable stoichiometries.
