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 less than or equal to x less than or equal to 0.4 were investigated using x-ray powder diffraction, D-E hysteresis, epsilon(r)(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 degrees C in the epsilon(r)(T) curve. It is suggested that this transition originates from the introduction of charged defects such as Na'(Pb) and Bi-Pb(.), resulting in the disturbance of long-range interactions among polar ordered BO6-octahedra and short-range structural order of charged defects (i. e., Na'(Pb) - Bi-Pb(.)). (C) 1999 American Institute of Physics. [S0021-8979(98)07024- 8].