  The perovskite (1-x)YMnO$_3$-xBiFeO$_3$ binary system is very promising
because of its multiferroic end members. Nanocrystalline phases have been
recently obtained by mechanosynthesis across the system, and the perovskite
structural evolution has been described. Two continuous solid solutions with
orthorhombic Pnma and rhombohedral R3c symmetries were found, which coexist
within a broad compositional interval of 0.5 < x < 0.9. This might be a
polar-nonpolar morphotropic phase boundary region, at which strong phase-change
magnetoelectric responses can be expected. A major issue is phase decomposition
at moderate temperatures that highly complicates ceramic processing. This is
required for carrying out a sound electrical characterization and also for
their use in devices. We present here the application of Spark Plasma Sintering
to the ceramic processing of YMnO$_3$-BiFeO$_3$ phases. This advanced
technique, when combined with nanocrystalline powders, allowed densifying
phases at reduced processing temperatures and times, so that perovskite
decomposition was avoided. Electrical measurements were accomplished, and the
response was shown to be mostly dominated by conduction. Nonetheless, the
intrinsic dielectric permittivity was obtained, and a distinctive enhancement
in the phase coexistence region was revealed. Besides, Rayleigh-type behaviour
characteristic of ferroelectrics was also demonstrated for all rhombohedral
phases. Magnetic characterization was performed in this region, and
antiferromagnetism was shown.
