Perovskite phase formation, microstructure and improvement of dielectric properties in iron-containing ferroelectrics

Pure perovskite-phase lead iron scandium niobate, Pb(Fe1/4Sc1/4Nb1/2)O-3 (PFScN), ceramics have been prepared by a conventional solid-state reaction method via a B-site oxide mixing route. Although synthesis conditions have been tailored to optimization, strong frequency dispersion of the dielectric properties cannot be improved by modifying ceramic processing, which is considered as correlating to the nature of iron-containing ferroelectrics. Sintering in an O-2 atmosphere and MnO2 and Li2CO3 dopings tend to decrease the dielectric loss of the iron-containing dielectrics. The strong frequency dispersion of the dielectric response and the abnormally recurrent increase of the dielectric constant and loss in the paraelectric region are correspondingly suppressed. This improvement of dielectric properties in the iron-containing ferroelectrics is interpreted by an electron compensation mechanism, in which the generation of donor electrons is based on different ionization paths. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.