Structure and dielectric properties of sodium-doped Ba(FeNb)0.5O3

The lower valence compensation of the Ba1-xNax(Fe0.5Nb0.5)(1+x/4)O-3 (x=0, 0.01, 0.05, 0.10, and 0.20) system was synthesized using a solid-state reaction, and the characteristics, including phase formation, microstructure and dielectric properties, were also investigated. XRD results indicate that the structure of BFN is cubic and transforms to orthorhombic when the Na+ ion concentration is >= 10 mol%. The SEM results indicate that the grain size of Ba1-xNax(Fe0.5Nb0.5)(1+x/4)O-3 samples increase from x=0.0 to 0.05, but decrease from 0.1 to 0.2 which is caused by the formation of acceptors Na-Ba2+(+)' at the grain boundaries that inhibits grain growth. Large and small grains coexist for Ba(FeNb)(0.5)O-3 doped with 5 mol% Na+ ions. The step-like dielectric relaxor curve obtained for the doping concentration is 10 mol%. The dielectric constant and loss of Ba1-xNax(Fe0.5Nb0.5)(1.025)O-3 ceramics are increased from 2 x 10(4)-10(5) to 6 x 10(4)-1.3 x 10(5) and 0.4-1.6 to 0.25 when x is increased from 0.1 to 0.2, respectively. Complex impedance spectroscopy indicated that the orientation and space charge polarization are dominant for the barrier layers Ba1-xNax(Fe0.5Nb0.5)(1+x/4)O-3 dielectric behavior. (C) 2010 Elsevier B.V. All rights reserved.