MARTENSITE LIKE PHASE TRANSITIONS DUE TO POLAR REGION STRUCTURE IN DISORDERED FERROELECTRIC CERAMICS
MARTENSITE-LIKE PHASE TRANSITIONS DUE TO POLAR REGION STRUCTURE IN DISORDERED FERROELECTRIC CERAMICS

Clear experimental evidence for phase transitions was shown in titanium doped lead magnesium niobate compositional disordered ferroelectric ceramics. One is the diffused phase transition around the temperature of dielectric permittivity maxima, which is often assumed as the characteristics of relaxor ferroelectrics. Another is a first order transition from frequency dispersion relaxor ferroelectrics to normal ferroelectrics, corresponding to a zero field spontaneous polar micro macrodomain switching. According to the x ray diffraction, thermal analysis and transmission electron microscope results, it is pointed out that the relaxor state corresponds to a coexistence of cubic parent phase and nucleating rhombohedral ferroelectric microregion which is similar to a precursor martensite. After the spontaneous relaxor normal ferroelectrics transition, the lower symmetry phase is sure to be a long range rhombohedral phase. Thus a dynamic behavior of polar microregions is suggested to explain the phenomena, which is more similar to a stress induced martensitic transformations from cubical stabilized perovskite parent phase.