Studies of the effects of defect distributions and mobility upon ferro-electric phase transformations were performed by means of transmission electron microscopy, high-resolution electron microscopy and dielectric spectroscopy. Defects which could be randomly quenched-in from temperatures that were significantly above that of the ferro-electric phase transformation resulted in a relaxor ferro-electric behavior that was characterized by polar nano-domains. However, defects which remained mobile, up to temperatures that were significantly lower than the phase transformation, resulted in a normal ferro-electric state which was characterized by domain pinning. Mobile impurities and vacancies were shown to order into chain fragments or clusters which diffused to domain boundaries and resulted in pinning of the boundaries during cooling.

Q.Tan, Z.Xu, J.F.Li, D.Viehland: Applied Physics Letters, 1997, 71[8], 1062-4