Charged defects and ferroelectricity in (1−x)PbZrO3−x(Na1/2Bi1/2)TiO3 solid solution

The crystal structure, dielectric/ferroelectric properties, and domain configuration of (1−x) PbZrO3−x(Na1/2Bi1/2)TiO3 solid solution with 0.14⩽x⩽0.4 were investigated using x-ray powder diffraction, D-E hysteresis, εr(T) measurements, and transmission electron microscopy. A sluggish transition from normal ferroelectric to relaxor state was observed as a function of composition. With an increasing amount of (Na1/2Bi1/2)TiO3, this transition was accompanied by changes in crystal structure (rhombohedral to pseudocubic), domain size and morphology (normal micron-size domain to polar nanodomain), and thermal phase transition behavior (normal ferroelectric transition to diffuse transition behavior with polarization relaxation). For intermediate compositions (i.e., x=0.25) between normal ferroelectric (x=0.16) and relaxor (x=0.4), a spontaneous relaxor-to-normal ferroelectric transition occurred at 80 °C in the εr(T) curve. It is suggested that this transition originates from the introduction of charged defects such as NaPb′ and BiPb•, resulting in the disturbance of long-range interactions among polar ordered BO6-octahedra and short-range structural order of charged defects (i.e., NaPb′−BiPb•).