Relaxor behavior and dielectric relaxation in Pb(Ba_(1/3)Nb_(2/3))O_3: A phase pure new relaxor material

摘要

Pb(Ba_(1/3)Nb_(2/3))O_3 was prepared by two steps solid state reaction route. Material stabilized in orthorhombic perovskite phase with lattice constants a=4.0849(3) ?, b=11.8469(4) ?, and c = 10.6818(9) ?. The scanning electron micrograph exhibits heterogeneous grain distribution with average grain size of 1-3 μm. Temperature dependent dielectric constant exhibits a broad peak at 316 K (ε_m=2250) that shows frequency dependent shifts toward higher temperature-typical relaxor behavior. Modified Curie-Weiss law is used to fit the dielectric data that exhibits almost complete diffuse phase transition characteristics. The dielectric relaxation obeys the Vogel-Fulcher relationship with the freezing temperature 286 K. In addition to relaxation observed due to transformation of the material into ergodic relaxor phase below Burn temperature, significant dielectric dispersion is observed in low frequency regime in both components of dielectric response and a small dielectric relaxation peak is observed in the temperature range (423-598 K) that is associated with defect related hopping process. Cole-Cole plots indicate polydispersive nature of this dielectric relaxation; the relaxation distribution increasing with temperature.