Dielectric anomalies in (Bax Sr1-x) 4 Nd2 Ti4 Nb6 O30 ceramics with various radius differences between A1 - And A2 -site ions

Abstract

Dielectric response of tetragonal tungsten bronze dielectrics (Bax Sr1-x) 4 Nd2 Ti4 Nb6 O30 was investigated over a broad temperature and frequency range, and the obvious composition-dependent dielectric anomalies with respect to x value were discussed in detail in association with the radius differences between A1 - and A2 -site ions. With decreasing the magnitude of radius difference between A1 - and A2 -site ions, the normal ferroelectric peak above 400 K became weaker, and two relaxor peaks at lower temperatures became obvious. The low- and high-temperature relaxor behaviors, which followed well the Vogel-Fulcher relationship, were associated with the polar clusters caused by the off-center NbTi displacements and the incommensurate tilting modulation, respectively. © 2007 American Institute of Physics.