A DIELECTRIC STUDY OF THE DOMAIN FREEZING IN KD2ASO4

The temperature- and frequency-dependent dielectric susceptibility of KD(2)ASO(4) was studied in the ferroelectric phase. A dispersion which is related to the dipole reversal was found in the high-frequency ran ge (10(7) Hz). The dispersion is described by a Gaussian distribution of relaxation times [1] which show Vogel-Fulcher temperature dependenc es. The high value of the dielectric constant below the phase transiti on is related to the mobility of the domain walls. This mobility steep ly decreases near the freezing temperature T-f and therefore a sudden decrease in the susceptibility takes place. A non-linear superposition of the piezoelectric resonance and the relaxational dispersion was ob served.