Ultrasonic studies of (CH3)2NH2Al(SO4)2 • 6H2O crystals irradiated by γ quanta and electrons

The temperature dependence of the longitudinal-ultrasound velocities in (CH3)(2)NH2Al(SO4)(2) . 6H(2)O crystals was studied using the echo-pulse technique in the 90-300 K range. The measurements were carried out along mutually perpendicular crystallographic directions X, Y, Z on samples both unirradiated and irradiated to various doses by gamma quanta and an electron beam. The ultrasound velocity V in this crystal was shown to be anisotropic, with V-YY > V-XX > V-ZZ. The V-XX= f (T), V-YY = f (T) , and V-ZZ = f (T) curves exhibit anomalies in the form of breaks at the ferroelectric phase transition (PT) at T-c1 = 152 K, as well as in the region of T-c2 = 218 K. It was established that as the irradiation dose increases, the PT temperature T-c1 decreases and the anomalies in the temperature dependences of the ultrasound velocities are smeared. (C) 2001 MAIK "Nauka/ Interperiodica".