Impedance spectroscopy of Bi4Ti3O12 ceramic produced by self-propagating high-temperature synthesis technique

Bi4Ti3O12 (bismuth titanate-BIT) ferroelectric ceramic was synthesized by self-propagating high-temperature synthesis (SHS) technique. The microstructure, electric and dielectric properties were determined and the results were compared to a reference sample produced by solid state reaction. The powders from SHS had agglomerated particles with average size of 200 nm. Bi4Ti3O12 100% crystalline phase was reached after SHS reaction followed by sintering at 1050 degreesC/2 h. The sintered bodies presented high relative density (98%) and small grain size (around 5 microns). The electrical and dielectric properties of the samples were studied using the impedance spectroscopy technique, and the three observed semicircles in the complex impedance diagrams were associated to the bulk, plate boundaries and grain boundaries of the sintered ceramics. The samples produced through SHS presented the same bulk conductivity as the reference one, and lower conductivity of the grain and plate boundaries. The same dielectric constant epsilon'= 200, at 300 degreesC and f = 1 MHz, was found for SHS sample and for the reference. For higher temperatures, at this same frequency, SHS samples presented higher relative permittivity than the reference, and for temperatures above T. both samples presented the same Curie-Weiss parameters. The differences observed in the electrical conductivity and relative permittivity, were attributed to the differences in the grain size and defect concentration. The anomaly in the permittivity curves near 550 degreesC is also discussed. (C) 2003 Elsevier Ltd. All rights reserved.