Behaviour of a polar relaxation mode around the phase transition point in the antiferroelectric PbZrO3 single crystal

In measurements of the dielectric dispersion carried out on single crystals of antiferroelectric lead zirconate (PbZrO3) a polar relaxation mode in the frequency range from 10(6) to 10(9) Hz has been found. Using the Cole-Cole relation for the complex epsilon(omega) response the relaxation frequency and dielectric step of the mode have been determined as functions of temperature. In the paraelectric phase the squared relaxation frequency well obeys a relation f(r)(2) similar to (T - T-0) with T-0 = 222.9 degrees C. The temperature dependence of the dielectric step corresponds to a sharp anomaly of the dielectric permittivity observed at the phase transition between the paraelectric and antiferroelectric states in PbZrO3. The phase transition mechanism of order-disorder type is discussed considering a disorder of the Pb sublattice in the paraelectric phase. It should be pointed out that similar dipolar relaxation in ABO(3) perovskites is known to appear only in those with ferroelectric properties.