DIELECTRIC-RELAXATION IN FERROELECTRIC (CH3)2NH2AL(SO4)26H2O CRYSTAL

This paper presents the results of the investigation of dielectric dispersion and ultrasonic velocity in the ferroelectric (CH3)2NH2A1(SO4)2. 6H2O crystal. The crystal shows a critical slowing down process of polarization with an extremely long relaxation time of the dipole system (τ= 1.66 10-7s at the phase transition point). The dielectric response over the frequency range up to 56 GHz in the paraelectric phase can be well described in terms of a monodispersive Debye-type formula. The activation energy of dipoles in the paraelectric phase is 0.11 eV = 8.5 kTc. The results show that the proper ferroelectric phase transition is nearly critical and of the order-disorder type. © 1991, Taylor & Francis Group, LLC. All rights reserved.