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

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Abstract
In measurements of the dielectric dispersion carried out on single crystals of antiferroelectric lead zirconate a polar relaxation mode in the frequency range from to has been found. Using the Cole - Cole relation for the complex 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 with . 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 . 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 perovskites is known to appear only in those with ferroelectric properties.