The depolarization decaying currents were measured for the PZT compound with morphotropic composition modified by the Fe1/3Sb2/3 cations, i.e., Pb[(Fe1/3Sb2/3)xTiyZrz]O3 with x + y + z = 1, x = 0,1, y = 0,44 (morphotropic boundary) and y = 0,47. The measurements were performed at room temperature and a few temperatures above (up to 473 K), as well as at a few lower temperatures (down to 77 K). The samples were poling at fields 0.02 kV/cm and 0.2 kV/cm at higher and lower temperatures, respectively. In the high temperature range, the time dependence depolarization current follows the fractional power law with two different exponents (n < 1 and m > 1), while in the low temperature range with a single exponent (n). The appropriate procedure has been used to transform the results obtained in the time domain into the frequency domain in order to calculate real and imaginary parts of the dielectric permittivity in the frequency range 5 x 105 - 0,1 Hz. The possible dielectric relaxation mechanisms have been discussed.
