  We consider a model of a nanocomposite based on non-interacting spherical
single-domain ferroelectric nanoparticles of various sizes embedded in a
dielectric matrix. The size distribution function of these nanoparticles is
selected as a part of the Gaussian distribution from minimum to maximum radius
(truncated normal distribution). For such nanocomposites, we calculate the
dependences of the reversible part of the electric polarization, the
electrocaloric temperature change, and the dielectric permittivity on the
external electric field, which have the characteristic form of hysteresis
loops. We then analyze the change in the shape of the hysteresis loops relative
to the particle size distribution parameters. We demonstrate that for the same
mean-square dispersion, the remanent polarization, coercive field, dielectric
permittivity maximums, maximums and minimums of the electrocaloric temperature
change depend most strongly on the most probable radius, moderately depend on
the dispersion, and have the weakest dependency on the nanoparticle maximum
radius. We calculated and analyzed the dependences of pyroelectric figures of
merit on the average radius of the nanoparticles in the composite. The
dependences confirm the presence of a phase transition induced by the size of
the nanoparticles, which is characterized by the presence of a maxima near the
critical average radius of the particles, the value of which increases with
increasing dispersion of the distribution function.
