Ferroelectric and antiferroelectric materials with pyrochlore structure

Abstract
Several compounds with the pyrochlore structure have been investigated. Dielectric and structural studies of the compound Cd2NB2O6S show the existence of three phase transitions at 106°C, 184°C and 282°C. The ferroelectric properties have been studied by several methods (x-Ray, DTA, dielectric and dilatometric methods, second harmonic generation). We also discuss some structural hypotheses. Bi2MIIIMvO7, oxides (MIII=Cr, Fe, In, Sc; Mv=Nb, Ta, Sb) with the cubic pyrochlore structure have been prepared. Some compounds exhibit broad maxima in the temperature dependence of the dielectric constant and the tangent of dielectric loss angle.