Dielectric behavior of spark plasma sintered BaTi0.7Zr0.3O3 relaxor ferroelectrics

In the present work we have studied the transport and dielectric behavior of BaTi0.7Zr0.3O3 (BTZ30) relaxor ferroelectrics prepared by spark plasma sintering. Nanocrystalline powder of BTZ30 was obtained by solid state reaction followed by mechanical milling. Fine and coarse-grained ceramics of BTZ30 were prepared by spark plasma sintering at 1100 and 1400 degrees C, respectively. The obtained materials were characterized by X-ray diffraction and scanning electron microscopy. The grain size of the BTZ30 ceramics increased from 200 nm to 3-5 mu m as the sintering temperature was increased from 1100 degrees C to 1400 degrees C. The electrical and dielectric properties of BTZ30 ceramics were studied by impedance spectroscopy over -150 to + 200 degrees C temperature range. The dielectric constant exhibits very large values > 10(5) for the spark plasma sintered ceramics associated with very high dielectric loss and electrical conductivity. The insulating nature of the BTZ30 ceramics could be retained by re-oxidation of the samples. The dielectric data of the annealed have been analyzed by the modified Curie-Weiss law and the relaxation process in the materials was fitted by Vogel-Fulcher model.