Preparation, structure and ferroelectric properties of Ba(Fe0.5Nb0.5)O3 powders by sol-gel method

Relaxor-type of ferroelectric material Ba(Fe1/2Nb1/2)O-3 were fabricated by a sol-gel technique. The powders of Ba(Fe1/2Nb1/2)O-3 heated at temperature greater than 550 degrees C were crystallized into a perovskite structure containing the pyrochlore phase. A pure perovskite phase was formed as the temperature increased to 850 degrees C. The activation energy of crystallization of Ba(Fe1/2Nb1/2)O-3 is 64.25kJ/mol calculated from Kissinger's equation. The average grain sizes increased with heating temperature (from 20 nm to 30 nm). The sample sintered at 1250 degrees C for 3 h, a dielectric constant, epsilon'(max) of similar to 20 000 and loss tangent of similar to 0.2 were obtained at room temperature. Among the measured temperature, BFN is observed to have higher dielectric constant in room temperature than PMN or PFN. From the hysteresis loops (P-E curve) a large remnant polarization P-r of 0.2 mu C/cm(2) and coercive field V, of 5 V/mu m, were measured. All of the properties clearly show that the BFN is a ferroelectric material. (c) 2005 Elsevier B.V. All rights reserved.