Study of Complex Ferroelectric and Antiferroelectric Systems

Rhombohedral (R), monoclinic (MA/MC) and tetragonal (T) phases are found in coexistence in a compositionally segregated xPb(In1/2Nb1/2)O3- yPb(Mg1/3Nb2/3)O3- zPbTiO3 (PIN-PMN-PT) (nominal composition x/y/z = 30/35/35) single crystal. Polarized light (PLM) measurements and X-ray diffraction (XRD) on both single crystal and ceramic series confirms the existence of 2 different monoclinic phases. A phase diagram in the MPB region of the PIN-PMN-PT solid solution is proposed based on both single crystals and ceramic material.Further study on the temperature driven rhombohedral (R) (R3m)  monoclinic (MA) phase transition in the single crystals and ceramics with MPB composition are carried out. It was found that the rhombohedral domain is able to return to its original state after annealed at above the RMA phase transition temperature (TR-M) but below the Currie temperature (TC). A polarization reversal model is proposed based on the polarization rotation theory.Solid solutions of (1-x)Pb(Mg1/2W1/2)O3-xPb(M1/2W1/2)O3(M = Zn2+ and Mn2+) have been prepared by solid state reaction with composition x up to 30% for Zn and 50% for Mn. The influence of Zn2+ and Mn2+ on structure, electrical and magnetic properties are revealed. (1-x)PbZrO3-xPb(Mn1/2W1/2)O3 (x = 0 - 0.1) as another new solid solution system was also prepared by the solid state reaction method. Its crystal structure, dielectric properties and antiferroelectricity were investigated and it was proven to be an excellent candidate for energy storage devices.In summary, the study for PIN-PMN-PT ternary solid solution near its MPB composition shall provide a general guideline for designing high performance peizocrystals. The study of PZ-based and PMW-based antiferroelectric solid solutions provided better understanding of antiferroelectric perovskites and provides a different approach for the design of soft antiferroelectric material with high energy density.