  We study electron transport properties of composite ferroelectrics ---
materials consisting of metallic grains embedded in a ferroelectric matrix. In
particular, we calculate the conductivity in a wide range of temperatures and
electric fields, showing pronounced hysteretic behavior. In weak fields,
electron cotunneling is the main transport mechanism. In this case, we show
that the ferroelectric matrix strongly influences the transport properties
through two effects: i) the dependence of the Coulomb gap on the dielectric
permittivity of the ferroelectric matrix, which in turn is controlled by
temperature and external field; and ii) the dependence of the tunneling matrix
elements on the electric polarization of the ferroelectric matrix, which can be
tuned by temperature and applied electric field as well. In the case of strong
electric fields, the Coulomb gap is suppressed and only the second mechanism is
important. Our results are important for i) thermometers for precise
temperature measurements and ii) ferrroelectric memristors.
