Structure, antiferro/ferro-electric transformation and relaxor behaviour in (1-x)Pb(Yb1/2Nb1/2)O3-xPb(Mg1/2W1/2)O3 ceramics

The superlattice structure and dielectric relaxor behaviour were simultaneously observed in (1-x)Pb(Yb1/2Nb1/2)O-3-xPb(Mg1/2W1/2)O-3 ((1-x)PYN-xPMW) ceramics composed by highly ordered end members. Orthorhombic perovskite structure was determined by X-ray diffraction for the compositions of x=00-02 and 08-10 with two sets of superlattice. For intermediate compositions, the superlattice peaks were still preserved with weakening in intensity. Strong dielectric relaxor behaviour seemed to be independent with the superlattice and well fitted by Vogel-Fulcher equation for x=03-07. It indicated that the polar microregions in (1-x)PYN-xPMW undergo the dipole glass-like and freezing state analogous to the prototypical relaxor Pb(Mg1/3Nb2/3)O-3. Slim ferroelectric hysteresis loops, seemingly made up with ferroelectric and antiferroelectric together, were obtained for the relaxor compositions using huge external field. The antiferroelectric compositions related to superlattice were determined through double ferroelectric polarisation loops. A schematic diagram was sketched to describe the structure transform and generation of relaxor behaviour.