A SYNCHROTRON X-RAY STUDY OF FERROELECTRIC SWITCHING, DOMAIN REVERSALAND PIEZOELECTRIC MODULI IN CSTIOASO4 UNDER AN APPLIED ELECTRIC-FIELD

Single crystals of caesium titanyl arsenate (CTA, CsTiOAsO4), with spa ce group Pna2(1) and isomorphous with potassium titanyl phosphate (KTP , KTiOPO4), have been studied using high-resolution synchrotron X-rays . During the experiments, an electric field was applied along the pola r axis [001]. Single-crystal plates, between 300 and 450 mu m thick al ong [001], were polarized by a variable square wave of frequency 20 Hz alternately applied to each side of the plate. A field-induced splitt ing of the + / - peaks for reflections hkl with l not equal 0 was obse rved. This splitting provides information about the coercive field, po larizability and the piezoelectric strain tenser. Two of the piezoelec tric coefficients of CTA could be estimated as d(31) similar or equal to 1 and d(33) similar or equal to 27 pm V-1. Whereas the coercive fie lds were estimated at 2300 Vmm(-1) the held necessary to reverse the d omains just once in CTA was found to be either 560 or 1550 V mm(-1), d epending on the polarity of the reversed domain in relation to the pol arity of the nonswitched part of the crystal.